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==================================
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How to use the QAPI code generator
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==================================
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2011-07-19 23:50:46 +04:00
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2021-07-21 02:56:17 +03:00
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..
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Copyright IBM Corp. 2011
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Copyright (C) 2012-2016 Red Hat, Inc.
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This work is licensed under the terms of the GNU GPL, version 2 or
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later. See the COPYING file in the top-level directory.
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Introduction
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============
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2011-07-19 23:50:46 +04:00
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QAPI is a native C API within QEMU which provides management-level
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functionality to internal and external users. For external
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users/processes, this interface is made available by a JSON-based wire
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format for the QEMU Monitor Protocol (QMP) for controlling qemu, as
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well as the QEMU Guest Agent (QGA) for communicating with the guest.
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The remainder of this document uses "Client JSON Protocol" when
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referring to the wire contents of a QMP or QGA connection.
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To map between Client JSON Protocol interfaces and the native C API,
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we generate C code from a QAPI schema. This document describes the
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QAPI schema language, and how it gets mapped to the Client JSON
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Protocol and to C. It additionally provides guidance on maintaining
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Client JSON Protocol compatibility.
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The QAPI schema language
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========================
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The QAPI schema defines the Client JSON Protocol's commands and
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events, as well as types used by them. Forward references are
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allowed.
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It is permissible for the schema to contain additional types not used
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by any commands or events, for the side effect of generated C code
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used internally.
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There are several kinds of types: simple types (a number of built-in
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types, such as ``int`` and ``str``; as well as enumerations), arrays,
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complex types (structs and unions), and alternate types (a choice
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between other types).
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Schema syntax
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-------------
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Syntax is loosely based on `JSON <http://www.ietf.org/rfc/rfc8259.txt>`_.
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Differences:
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* Comments: start with a hash character (``#``) that is not part of a
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string, and extend to the end of the line.
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* Strings are enclosed in ``'single quotes'``, not ``"double quotes"``.
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* Strings are restricted to printable ASCII, and escape sequences to
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just ``\\``.
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* Numbers and ``null`` are not supported.
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A second layer of syntax defines the sequences of JSON texts that are
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a correctly structured QAPI schema. We provide a grammar for this
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syntax in an EBNF-like notation:
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* Production rules look like ``non-terminal = expression``
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* Concatenation: expression ``A B`` matches expression ``A``, then ``B``
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* Alternation: expression ``A | B`` matches expression ``A`` or ``B``
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* Repetition: expression ``A...`` matches zero or more occurrences of
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expression ``A``
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* Repetition: expression ``A, ...`` matches zero or more occurrences of
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expression ``A`` separated by ``,``
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* Grouping: expression ``( A )`` matches expression ``A``
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* JSON's structural characters are terminals: ``{ } [ ] : ,``
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* JSON's literal names are terminals: ``false true``
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* String literals enclosed in ``'single quotes'`` are terminal, and match
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this JSON string, with a leading ``*`` stripped off
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* When JSON object member's name starts with ``*``, the member is
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optional.
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* The symbol ``STRING`` is a terminal, and matches any JSON string
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* The symbol ``BOOL`` is a terminal, and matches JSON ``false`` or ``true``
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* ALL-CAPS words other than ``STRING`` are non-terminals
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The order of members within JSON objects does not matter unless
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explicitly noted.
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A QAPI schema consists of a series of top-level expressions::
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SCHEMA = TOP-LEVEL-EXPR...
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The top-level expressions are all JSON objects. Code and
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documentation is generated in schema definition order. Code order
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should not matter.
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A top-level expressions is either a directive or a definition::
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TOP-LEVEL-EXPR = DIRECTIVE | DEFINITION
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There are two kinds of directives and six kinds of definitions::
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DIRECTIVE = INCLUDE | PRAGMA
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DEFINITION = ENUM | STRUCT | UNION | ALTERNATE | COMMAND | EVENT
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These are discussed in detail below.
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Built-in Types
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--------------
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The following types are predefined, and map to C as follows:
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============= ============== ============================================
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Schema C JSON
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============= ============== ============================================
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``str`` ``char *`` any JSON string, UTF-8
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``number`` ``double`` any JSON number
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``int`` ``int64_t`` a JSON number without fractional part
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that fits into the C integer type
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``int8`` ``int8_t`` likewise
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``int16`` ``int16_t`` likewise
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``int32`` ``int32_t`` likewise
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``int64`` ``int64_t`` likewise
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``uint8`` ``uint8_t`` likewise
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``uint16`` ``uint16_t`` likewise
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``uint32`` ``uint32_t`` likewise
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``uint64`` ``uint64_t`` likewise
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``size`` ``uint64_t`` like ``uint64_t``, except
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``StringInputVisitor`` accepts size suffixes
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``bool`` ``bool`` JSON ``true`` or ``false``
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``null`` ``QNull *`` JSON ``null``
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``any`` ``QObject *`` any JSON value
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``QType`` ``QType`` JSON string matching enum ``QType`` values
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============= ============== ============================================
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2014-05-07 22:46:15 +04:00
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Include directives
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------------------
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Syntax::
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INCLUDE = { 'include': STRING }
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The QAPI schema definitions can be modularized using the 'include' directive::
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{ 'include': 'path/to/file.json' }
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The directive is evaluated recursively, and include paths are relative
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to the file using the directive. Multiple includes of the same file
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are idempotent.
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As a matter of style, it is a good idea to have all files be
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self-contained, but at the moment, nothing prevents an included file
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from making a forward reference to a type that is only introduced by
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an outer file. The parser may be made stricter in the future to
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prevent incomplete include files.
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.. _pragma:
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Pragma directives
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-----------------
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Syntax::
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PRAGMA = { 'pragma': {
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'*doc-required': BOOL,
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'*command-name-exceptions': [ STRING, ... ],
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'*command-returns-exceptions': [ STRING, ... ],
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'*member-name-exceptions': [ STRING, ... ] } }
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The pragma directive lets you control optional generator behavior.
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Pragma's scope is currently the complete schema. Setting the same
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pragma to different values in parts of the schema doesn't work.
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Pragma 'doc-required' takes a boolean value. If true, documentation
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is required. Default is false.
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Pragma 'command-name-exceptions' takes a list of commands whose names
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may contain ``"_"`` instead of ``"-"``. Default is none.
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Pragma 'command-returns-exceptions' takes a list of commands that may
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violate the rules on permitted return types. Default is none.
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Pragma 'member-name-exceptions' takes a list of types whose member
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names may contain uppercase letters, and ``"_"`` instead of ``"-"``.
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Default is none.
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.. _ENUM-VALUE:
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Enumeration types
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-----------------
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Syntax::
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ENUM = { 'enum': STRING,
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'data': [ ENUM-VALUE, ... ],
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'*prefix': STRING,
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'*if': COND,
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'*features': FEATURES }
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ENUM-VALUE = STRING
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'*if': COND,
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'*features': FEATURES }
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Member 'enum' names the enum type.
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Each member of the 'data' array defines a value of the enumeration
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type. The form STRING is shorthand for :code:`{ 'name': STRING }`. The
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'name' values must be be distinct.
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Example::
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{ 'enum': 'MyEnum', 'data': [ 'value1', 'value2', 'value3' ] }
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Nothing prevents an empty enumeration, although it is probably not
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useful.
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On the wire, an enumeration type's value is represented by its
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(string) name. In C, it's represented by an enumeration constant.
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These are of the form PREFIX_NAME, where PREFIX is derived from the
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enumeration type's name, and NAME from the value's name. For the
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example above, the generator maps 'MyEnum' to MY_ENUM and 'value1' to
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VALUE1, resulting in the enumeration constant MY_ENUM_VALUE1. The
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optional 'prefix' member overrides PREFIX.
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The generated C enumeration constants have values 0, 1, ..., N-1 (in
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QAPI schema order), where N is the number of values. There is an
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additional enumeration constant PREFIX__MAX with value N.
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Do not use string or an integer type when an enumeration type can do
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the job satisfactorily.
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The optional 'if' member specifies a conditional. See `Configuring the
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schema`_ below for more on this.
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The optional 'features' member specifies features. See Features_
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below for more on this.
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.. _TYPE-REF:
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Type references and array types
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-------------------------------
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Syntax::
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TYPE-REF = STRING | ARRAY-TYPE
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ARRAY-TYPE = [ STRING ]
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A string denotes the type named by the string.
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A one-element array containing a string denotes an array of the type
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named by the string. Example: ``['int']`` denotes an array of ``int``.
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Struct types
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------------
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Syntax::
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STRUCT = { 'struct': STRING,
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'data': MEMBERS,
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'*base': STRING,
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'*if': COND,
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'*features': FEATURES }
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MEMBERS = { MEMBER, ... }
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MEMBER = STRING : TYPE-REF
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| STRING : { 'type': TYPE-REF,
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'*if': COND,
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'*features': FEATURES }
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Member 'struct' names the struct type.
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Each MEMBER of the 'data' object defines a member of the struct type.
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.. _MEMBERS:
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The MEMBER's STRING name consists of an optional ``*`` prefix and the
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struct member name. If ``*`` is present, the member is optional.
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The MEMBER's value defines its properties, in particular its type.
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The form TYPE-REF_ is shorthand for :code:`{ 'type': TYPE-REF }`.
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Example::
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{ 'struct': 'MyType',
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'data': { 'member1': 'str', 'member2': ['int'], '*member3': 'str' } }
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A struct type corresponds to a struct in C, and an object in JSON.
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The C struct's members are generated in QAPI schema order.
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The optional 'base' member names a struct type whose members are to be
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|
|
included in this type. They go first in the C struct.
|
2013-09-19 13:56:36 +04:00
|
|
|
|
2021-07-21 02:56:17 +03:00
|
|
|
Example::
|
2019-09-13 23:13:48 +03:00
|
|
|
|
|
|
|
{ 'struct': 'BlockdevOptionsGenericFormat',
|
|
|
|
'data': { 'file': 'str' } }
|
2015-05-04 18:05:26 +03:00
|
|
|
{ 'struct': 'BlockdevOptionsGenericCOWFormat',
|
2013-09-19 13:56:36 +04:00
|
|
|
'base': 'BlockdevOptionsGenericFormat',
|
|
|
|
'data': { '*backing': 'str' } }
|
|
|
|
|
|
|
|
An example BlockdevOptionsGenericCOWFormat object on the wire could use
|
2021-07-21 02:56:17 +03:00
|
|
|
both members like this::
|
2013-09-19 13:56:36 +04:00
|
|
|
|
|
|
|
{ "file": "/some/place/my-image",
|
|
|
|
"backing": "/some/place/my-backing-file" }
|
|
|
|
|
2021-07-21 02:56:19 +03:00
|
|
|
The optional 'if' member specifies a conditional. See `Configuring
|
|
|
|
the schema`_ below for more on this.
|
2019-09-13 23:13:48 +03:00
|
|
|
|
2021-07-21 02:56:19 +03:00
|
|
|
The optional 'features' member specifies features. See Features_
|
2019-09-13 23:13:48 +03:00
|
|
|
below for more on this.
|
|
|
|
|
2015-05-04 18:04:59 +03:00
|
|
|
|
2021-07-21 02:56:17 +03:00
|
|
|
Union types
|
|
|
|
-----------
|
|
|
|
|
|
|
|
Syntax::
|
2013-07-16 15:17:27 +04:00
|
|
|
|
2019-09-13 23:13:48 +03:00
|
|
|
UNION = { 'union': STRING,
|
|
|
|
'base': ( MEMBERS | STRING ),
|
|
|
|
'discriminator': STRING,
|
2021-09-17 17:31:32 +03:00
|
|
|
'data': BRANCHES,
|
2020-03-17 14:54:37 +03:00
|
|
|
'*if': COND,
|
|
|
|
'*features': FEATURES }
|
2019-09-13 23:13:48 +03:00
|
|
|
BRANCHES = { BRANCH, ... }
|
|
|
|
BRANCH = STRING : TYPE-REF
|
|
|
|
| STRING : { 'type': TYPE-REF, '*if': COND }
|
|
|
|
|
|
|
|
Member 'union' names the union type.
|
2013-07-16 15:17:27 +04:00
|
|
|
|
2021-09-17 17:31:32 +03:00
|
|
|
The 'base' member defines the common members. If it is a MEMBERS_
|
|
|
|
object, it defines common members just like a struct type's 'data'
|
|
|
|
member defines struct type members. If it is a STRING, it names a
|
|
|
|
struct type whose members are the common members.
|
|
|
|
|
|
|
|
Member 'discriminator' must name a non-optional enum-typed member of
|
|
|
|
the base struct. That member's value selects a branch by its name.
|
|
|
|
If no such branch exists, an empty branch is assumed.
|
2019-09-13 23:13:48 +03:00
|
|
|
|
|
|
|
Each BRANCH of the 'data' object defines a branch of the union. A
|
|
|
|
union must have at least one branch.
|
|
|
|
|
2021-09-17 17:31:32 +03:00
|
|
|
The BRANCH's STRING name is the branch name. It must be a value of
|
|
|
|
the discriminator enum type.
|
2019-09-13 23:13:48 +03:00
|
|
|
|
|
|
|
The BRANCH's value defines the branch's properties, in particular its
|
2021-09-17 17:31:32 +03:00
|
|
|
type. The type must a struct type. The form TYPE-REF_ is shorthand
|
|
|
|
for :code:`{ 'type': TYPE-REF }`.
|
2019-09-13 23:13:48 +03:00
|
|
|
|
2021-09-17 17:31:32 +03:00
|
|
|
In the Client JSON Protocol, a union is represented by an object with
|
|
|
|
the common members (from the base type) and the selected branch's
|
|
|
|
members. The two sets of member names must be disjoint.
|
2019-09-13 23:13:48 +03:00
|
|
|
|
2021-09-17 17:31:32 +03:00
|
|
|
Example::
|
2013-07-03 17:58:57 +04:00
|
|
|
|
2015-09-03 11:18:06 +03:00
|
|
|
{ 'enum': 'BlockdevDriver', 'data': [ 'file', 'qcow2' ] }
|
2013-07-03 17:58:57 +04:00
|
|
|
{ 'union': 'BlockdevOptions',
|
2016-03-18 01:48:39 +03:00
|
|
|
'base': { 'driver': 'BlockdevDriver', '*read-only': 'bool' },
|
2013-07-03 17:58:57 +04:00
|
|
|
'discriminator': 'driver',
|
2016-03-18 01:48:38 +03:00
|
|
|
'data': { 'file': 'BlockdevOptionsFile',
|
|
|
|
'qcow2': 'BlockdevOptionsQcow2' } }
|
2013-07-03 17:58:57 +04:00
|
|
|
|
2021-07-21 02:56:17 +03:00
|
|
|
Resulting in these JSON objects::
|
2015-05-04 18:04:59 +03:00
|
|
|
|
2016-03-18 01:48:38 +03:00
|
|
|
{ "driver": "file", "read-only": true,
|
2015-05-04 18:04:59 +03:00
|
|
|
"filename": "/some/place/my-image" }
|
2016-03-18 01:48:38 +03:00
|
|
|
{ "driver": "qcow2", "read-only": false,
|
|
|
|
"backing": "/some/place/my-image", "lazy-refcounts": true }
|
2015-05-04 18:04:59 +03:00
|
|
|
|
2021-09-17 17:31:32 +03:00
|
|
|
The order of branches need not match the order of the enum values.
|
|
|
|
The branches need not cover all possible enum values. In the
|
|
|
|
resulting generated C data types, a union is represented as a struct
|
|
|
|
with the base members in QAPI schema order, and then a union of
|
|
|
|
structures for each branch of the struct.
|
2013-07-08 18:14:21 +04:00
|
|
|
|
2021-07-21 02:56:19 +03:00
|
|
|
The optional 'if' member specifies a conditional. See `Configuring
|
|
|
|
the schema`_ below for more on this.
|
2019-09-13 23:13:48 +03:00
|
|
|
|
2021-07-21 02:56:19 +03:00
|
|
|
The optional 'features' member specifies features. See Features_
|
2020-03-17 14:54:37 +03:00
|
|
|
below for more on this.
|
|
|
|
|
2015-05-04 18:04:59 +03:00
|
|
|
|
2021-07-21 02:56:17 +03:00
|
|
|
Alternate types
|
|
|
|
---------------
|
|
|
|
|
|
|
|
Syntax::
|
2013-07-08 18:14:21 +04:00
|
|
|
|
2019-09-13 23:13:48 +03:00
|
|
|
ALTERNATE = { 'alternate': STRING,
|
|
|
|
'data': ALTERNATIVES,
|
2020-03-17 14:54:37 +03:00
|
|
|
'*if': COND,
|
|
|
|
'*features': FEATURES }
|
2019-09-13 23:13:48 +03:00
|
|
|
ALTERNATIVES = { ALTERNATIVE, ... }
|
2020-03-09 17:26:38 +03:00
|
|
|
ALTERNATIVE = STRING : STRING
|
2019-09-13 23:13:48 +03:00
|
|
|
| STRING : { 'type': STRING, '*if': COND }
|
|
|
|
|
|
|
|
Member 'alternate' names the alternate type.
|
|
|
|
|
|
|
|
Each ALTERNATIVE of the 'data' object defines a branch of the
|
|
|
|
alternate. An alternate must have at least one branch.
|
2015-05-04 18:05:12 +03:00
|
|
|
|
2019-09-13 23:13:48 +03:00
|
|
|
The ALTERNATIVE's STRING name is the branch name.
|
|
|
|
|
|
|
|
The ALTERNATIVE's value defines the branch's properties, in particular
|
2021-07-21 02:56:18 +03:00
|
|
|
its type. The form STRING is shorthand for :code:`{ 'type': STRING }`.
|
2019-09-13 23:13:48 +03:00
|
|
|
|
2021-07-21 02:56:17 +03:00
|
|
|
Example::
|
2015-05-04 18:05:12 +03:00
|
|
|
|
2016-03-18 01:48:38 +03:00
|
|
|
{ 'alternate': 'BlockdevRef',
|
2013-07-08 18:14:21 +04:00
|
|
|
'data': { 'definition': 'BlockdevOptions',
|
|
|
|
'reference': 'str' } }
|
|
|
|
|
2019-09-13 23:13:48 +03:00
|
|
|
An alternate type is like a union type, except there is no
|
|
|
|
discriminator on the wire. Instead, the branch to use is inferred
|
|
|
|
from the value. An alternate can only express a choice between types
|
|
|
|
represented differently on the wire.
|
|
|
|
|
|
|
|
If a branch is typed as the 'bool' built-in, the alternate accepts
|
|
|
|
true and false; if it is typed as any of the various numeric
|
2015-05-04 18:05:35 +03:00
|
|
|
built-ins, it accepts a JSON number; if it is typed as a 'str'
|
2017-06-26 20:25:14 +03:00
|
|
|
built-in or named enum type, it accepts a JSON string; if it is typed
|
|
|
|
as the 'null' built-in, it accepts JSON null; and if it is typed as a
|
2019-09-13 23:13:48 +03:00
|
|
|
complex type (struct or union), it accepts a JSON object.
|
2015-05-04 18:05:12 +03:00
|
|
|
|
|
|
|
The example alternate declaration above allows using both of the
|
2021-07-21 02:56:17 +03:00
|
|
|
following example objects::
|
2013-07-08 18:14:21 +04:00
|
|
|
|
|
|
|
{ "file": "my_existing_block_device_id" }
|
|
|
|
{ "file": { "driver": "file",
|
2016-03-18 01:48:38 +03:00
|
|
|
"read-only": false,
|
2013-10-19 20:52:33 +04:00
|
|
|
"filename": "/tmp/mydisk.qcow2" } }
|
2013-07-08 18:14:21 +04:00
|
|
|
|
2021-07-21 02:56:19 +03:00
|
|
|
The optional 'if' member specifies a conditional. See `Configuring
|
|
|
|
the schema`_ below for more on this.
|
2019-09-13 23:13:48 +03:00
|
|
|
|
2021-07-21 02:56:19 +03:00
|
|
|
The optional 'features' member specifies features. See Features_
|
2020-03-17 14:54:37 +03:00
|
|
|
below for more on this.
|
|
|
|
|
2013-07-08 18:14:21 +04:00
|
|
|
|
2021-07-21 02:56:17 +03:00
|
|
|
Commands
|
|
|
|
--------
|
|
|
|
|
|
|
|
Syntax::
|
2011-07-19 23:50:46 +04:00
|
|
|
|
2019-09-13 23:13:48 +03:00
|
|
|
COMMAND = { 'command': STRING,
|
|
|
|
(
|
|
|
|
'*data': ( MEMBERS | STRING ),
|
|
|
|
|
|
|
|
|
'data': STRING,
|
|
|
|
'boxed': true,
|
|
|
|
)
|
|
|
|
'*returns': TYPE-REF,
|
|
|
|
'*success-response': false,
|
|
|
|
'*gen': false,
|
|
|
|
'*allow-oob': true,
|
|
|
|
'*allow-preconfig': true,
|
2020-10-05 18:58:49 +03:00
|
|
|
'*coroutine': true,
|
2019-10-18 11:14:51 +03:00
|
|
|
'*if': COND,
|
|
|
|
'*features': FEATURES }
|
2019-09-13 23:13:48 +03:00
|
|
|
|
|
|
|
Member 'command' names the command.
|
|
|
|
|
2021-07-21 02:56:19 +03:00
|
|
|
Member 'data' defines the arguments. It defaults to an empty MEMBERS_
|
2019-09-13 23:13:48 +03:00
|
|
|
object.
|
|
|
|
|
2021-07-21 02:56:19 +03:00
|
|
|
If 'data' is a MEMBERS_ object, then MEMBERS defines arguments just
|
2019-09-13 23:13:48 +03:00
|
|
|
like a struct type's 'data' defines struct type members.
|
|
|
|
|
|
|
|
If 'data' is a STRING, then STRING names a complex type whose members
|
2021-07-21 02:56:18 +03:00
|
|
|
are the arguments. A union type requires ``'boxed': true``.
|
2019-09-13 23:13:48 +03:00
|
|
|
|
|
|
|
Member 'returns' defines the command's return type. It defaults to an
|
|
|
|
empty struct type. It must normally be a complex type or an array of
|
|
|
|
a complex type. To return anything else, the command must be listed
|
2021-03-23 12:40:16 +03:00
|
|
|
in pragma 'commands-returns-exceptions'. If you do this, extending
|
|
|
|
the command to return additional information will be harder. Use of
|
|
|
|
the pragma for new commands is strongly discouraged.
|
2015-05-04 18:05:35 +03:00
|
|
|
|
2019-09-13 23:13:48 +03:00
|
|
|
A command's error responses are not specified in the QAPI schema.
|
|
|
|
Error conditions should be documented in comments.
|
|
|
|
|
|
|
|
In the Client JSON Protocol, the value of the "execute" or "exec-oob"
|
|
|
|
member is the command name. The value of the "arguments" member then
|
|
|
|
has to conform to the arguments, and the value of the success
|
|
|
|
response's "return" member will conform to the return type.
|
2015-05-04 18:04:59 +03:00
|
|
|
|
2021-07-21 02:56:17 +03:00
|
|
|
Some example commands::
|
2015-05-04 18:04:59 +03:00
|
|
|
|
|
|
|
{ 'command': 'my-first-command',
|
|
|
|
'data': { 'arg1': 'str', '*arg2': 'str' } }
|
2015-05-04 18:05:26 +03:00
|
|
|
{ 'struct': 'MyType', 'data': { '*value': 'str' } }
|
2015-05-04 18:04:59 +03:00
|
|
|
{ 'command': 'my-second-command',
|
|
|
|
'returns': [ 'MyType' ] }
|
|
|
|
|
2021-07-21 02:56:17 +03:00
|
|
|
which would validate this Client JSON Protocol transaction::
|
2015-05-04 18:04:59 +03:00
|
|
|
|
|
|
|
=> { "execute": "my-first-command",
|
|
|
|
"arguments": { "arg1": "hello" } }
|
|
|
|
<= { "return": { } }
|
|
|
|
=> { "execute": "my-second-command" }
|
|
|
|
<= { "return": [ { "value": "one" }, { } ] }
|
|
|
|
|
2019-09-13 23:13:48 +03:00
|
|
|
The generator emits a prototype for the C function implementing the
|
|
|
|
command. The function itself needs to be written by hand. See
|
2021-07-21 02:56:19 +03:00
|
|
|
section `Code generated for commands`_ for examples.
|
2019-09-13 23:13:48 +03:00
|
|
|
|
|
|
|
The function returns the return type. When member 'boxed' is absent,
|
|
|
|
it takes the command arguments as arguments one by one, in QAPI schema
|
|
|
|
order. Else it takes them wrapped in the C struct generated for the
|
2021-07-21 02:56:18 +03:00
|
|
|
complex argument type. It takes an additional ``Error **`` argument in
|
2019-09-13 23:13:48 +03:00
|
|
|
either case.
|
2016-07-14 06:50:20 +03:00
|
|
|
|
|
|
|
The generator also emits a marshalling function that extracts
|
|
|
|
arguments for the user's function out of an input QDict, calls the
|
|
|
|
user's function, and if it succeeded, builds an output QObject from
|
2019-09-13 23:13:48 +03:00
|
|
|
its return value. This is for use by the QMP monitor core.
|
2016-07-14 06:50:20 +03:00
|
|
|
|
2015-05-04 18:04:59 +03:00
|
|
|
In rare cases, QAPI cannot express a type-safe representation of a
|
2015-09-16 14:06:27 +03:00
|
|
|
corresponding Client JSON Protocol command. You then have to suppress
|
2019-09-13 23:13:48 +03:00
|
|
|
generation of a marshalling function by including a member 'gen' with
|
2018-07-03 11:53:58 +03:00
|
|
|
boolean value false, and instead write your own function. For
|
2021-07-21 02:56:17 +03:00
|
|
|
example::
|
2015-05-04 18:04:59 +03:00
|
|
|
|
|
|
|
{ 'command': 'netdev_add',
|
2015-09-16 14:06:26 +03:00
|
|
|
'data': {'type': 'str', 'id': 'str'},
|
2015-05-04 18:04:59 +03:00
|
|
|
'gen': false }
|
|
|
|
|
2018-07-03 11:53:58 +03:00
|
|
|
Please try to avoid adding new commands that rely on this, and instead
|
|
|
|
use type-safe unions.
|
|
|
|
|
2015-05-04 18:04:59 +03:00
|
|
|
Normally, the QAPI schema is used to describe synchronous exchanges,
|
|
|
|
where a response is expected. But in some cases, the action of a
|
|
|
|
command is expected to change state in a way that a successful
|
2019-09-13 23:13:48 +03:00
|
|
|
response is not possible (although the command will still return an
|
|
|
|
error object on failure). When a successful reply is not possible,
|
|
|
|
the command definition includes the optional member 'success-response'
|
|
|
|
with boolean value false. So far, only QGA makes use of this member.
|
2011-07-19 23:50:46 +04:00
|
|
|
|
2019-09-13 23:13:48 +03:00
|
|
|
Member 'allow-oob' declares whether the command supports out-of-band
|
2021-07-21 02:56:17 +03:00
|
|
|
(OOB) execution. It defaults to false. For example::
|
2018-03-09 11:59:44 +03:00
|
|
|
|
|
|
|
{ 'command': 'migrate_recover',
|
|
|
|
'data': { 'uri': 'str' }, 'allow-oob': true }
|
|
|
|
|
2023-05-15 19:22:43 +03:00
|
|
|
See the :doc:`/interop/qmp-spec` for out-of-band execution syntax
|
|
|
|
and semantics.
|
2018-03-09 11:59:44 +03:00
|
|
|
|
2018-07-03 11:53:58 +03:00
|
|
|
Commands supporting out-of-band execution can still be executed
|
|
|
|
in-band.
|
2018-03-09 11:59:44 +03:00
|
|
|
|
2018-07-03 11:53:58 +03:00
|
|
|
When a command is executed in-band, its handler runs in the main
|
|
|
|
thread with the BQL held.
|
2018-03-09 11:59:44 +03:00
|
|
|
|
2018-07-03 11:53:58 +03:00
|
|
|
When a command is executed out-of-band, its handler runs in a
|
|
|
|
dedicated monitor I/O thread with the BQL *not* held.
|
2018-03-09 11:59:44 +03:00
|
|
|
|
2018-07-03 11:53:58 +03:00
|
|
|
An OOB-capable command handler must satisfy the following conditions:
|
2018-03-09 11:59:44 +03:00
|
|
|
|
2018-07-03 11:53:58 +03:00
|
|
|
- It terminates quickly.
|
|
|
|
- It does not invoke system calls that may block.
|
2018-03-09 11:59:44 +03:00
|
|
|
- It does not access guest RAM that may block when userfaultfd is
|
2018-07-03 11:53:58 +03:00
|
|
|
enabled for postcopy live migration.
|
2018-06-20 10:32:21 +03:00
|
|
|
- It takes only "fast" locks, i.e. all critical sections protected by
|
|
|
|
any lock it takes also satisfy the conditions for OOB command
|
|
|
|
handler code.
|
|
|
|
|
|
|
|
The restrictions on locking limit access to shared state. Such access
|
|
|
|
requires synchronization, but OOB commands can't take the BQL or any
|
|
|
|
other "slow" lock.
|
2018-03-09 11:59:44 +03:00
|
|
|
|
2018-07-03 11:53:58 +03:00
|
|
|
When in doubt, do not implement OOB execution support.
|
2011-07-19 23:50:46 +04:00
|
|
|
|
2019-09-13 23:13:48 +03:00
|
|
|
Member 'allow-preconfig' declares whether the command is available
|
2021-07-21 02:56:17 +03:00
|
|
|
before the machine is built. It defaults to false. For example::
|
2018-05-11 19:51:43 +03:00
|
|
|
|
2020-10-27 15:10:26 +03:00
|
|
|
{ 'enum': 'QMPCapability',
|
|
|
|
'data': [ 'oob' ] }
|
2018-05-11 19:51:43 +03:00
|
|
|
{ 'command': 'qmp_capabilities',
|
|
|
|
'data': { '*enable': [ 'QMPCapability' ] },
|
|
|
|
'allow-preconfig': true }
|
|
|
|
|
2018-07-03 11:53:58 +03:00
|
|
|
QMP is available before the machine is built only when QEMU was
|
|
|
|
started with --preconfig.
|
|
|
|
|
2020-10-05 18:58:49 +03:00
|
|
|
Member 'coroutine' tells the QMP dispatcher whether the command handler
|
|
|
|
is safe to be run in a coroutine. It defaults to false. If it is true,
|
|
|
|
the command handler is called from coroutine context and may yield while
|
|
|
|
waiting for an external event (such as I/O completion) in order to avoid
|
|
|
|
blocking the guest and other background operations.
|
|
|
|
|
|
|
|
Coroutine safety can be hard to prove, similar to thread safety. Common
|
|
|
|
pitfalls are:
|
|
|
|
|
2024-01-02 18:35:29 +03:00
|
|
|
- The BQL isn't held across ``qemu_coroutine_yield()``, so
|
2020-10-05 18:58:49 +03:00
|
|
|
operations that used to assume that they execute atomically may have
|
|
|
|
to be more careful to protect against changes in the global state.
|
|
|
|
|
2021-07-21 02:56:18 +03:00
|
|
|
- Nested event loops (``AIO_WAIT_WHILE()`` etc.) are problematic in
|
2020-10-05 18:58:49 +03:00
|
|
|
coroutine context and can easily lead to deadlocks. They should be
|
|
|
|
replaced by yielding and reentering the coroutine when the condition
|
|
|
|
becomes false.
|
|
|
|
|
|
|
|
Since the command handler may assume coroutine context, any callers
|
|
|
|
other than the QMP dispatcher must also call it in coroutine context.
|
2020-10-05 18:58:51 +03:00
|
|
|
In particular, HMP commands calling such a QMP command handler must be
|
2021-07-21 02:56:18 +03:00
|
|
|
marked ``.coroutine = true`` in hmp-commands.hx.
|
2020-10-05 18:58:49 +03:00
|
|
|
|
2021-07-21 02:56:18 +03:00
|
|
|
It is an error to specify both ``'coroutine': true`` and ``'allow-oob': true``
|
2020-10-05 18:58:49 +03:00
|
|
|
for a command. We don't currently have a use case for both together and
|
|
|
|
without a use case, it's not entirely clear what the semantics should
|
|
|
|
be.
|
|
|
|
|
2021-07-21 02:56:19 +03:00
|
|
|
The optional 'if' member specifies a conditional. See `Configuring
|
|
|
|
the schema`_ below for more on this.
|
2019-09-13 23:13:48 +03:00
|
|
|
|
2021-07-21 02:56:19 +03:00
|
|
|
The optional 'features' member specifies features. See Features_
|
2020-03-17 14:54:37 +03:00
|
|
|
below for more on this.
|
|
|
|
|
2019-09-13 23:13:48 +03:00
|
|
|
|
2021-07-21 02:56:17 +03:00
|
|
|
Events
|
|
|
|
------
|
|
|
|
|
|
|
|
Syntax::
|
2014-06-18 10:43:28 +04:00
|
|
|
|
2019-09-13 23:13:48 +03:00
|
|
|
EVENT = { 'event': STRING,
|
|
|
|
(
|
|
|
|
'*data': ( MEMBERS | STRING ),
|
|
|
|
|
|
|
|
|
'data': STRING,
|
|
|
|
'boxed': true,
|
|
|
|
)
|
2020-03-17 14:54:37 +03:00
|
|
|
'*if': COND,
|
|
|
|
'*features': FEATURES }
|
2019-09-13 23:13:48 +03:00
|
|
|
|
|
|
|
Member 'event' names the event. This is the event name used in the
|
|
|
|
Client JSON Protocol.
|
|
|
|
|
|
|
|
Member 'data' defines the event-specific data. It defaults to an
|
|
|
|
empty MEMBERS object.
|
|
|
|
|
|
|
|
If 'data' is a MEMBERS object, then MEMBERS defines event-specific
|
|
|
|
data just like a struct type's 'data' defines struct type members.
|
2015-05-04 18:04:59 +03:00
|
|
|
|
2019-09-13 23:13:48 +03:00
|
|
|
If 'data' is a STRING, then STRING names a complex type whose members
|
2021-07-21 02:56:18 +03:00
|
|
|
are the event-specific data. A union type requires ``'boxed': true``.
|
2014-06-18 10:43:28 +04:00
|
|
|
|
2021-07-21 02:56:17 +03:00
|
|
|
An example event is::
|
2014-06-18 10:43:28 +04:00
|
|
|
|
2021-07-21 02:56:17 +03:00
|
|
|
{ 'event': 'EVENT_C',
|
|
|
|
'data': { '*a': 'int', 'b': 'str' } }
|
2014-06-18 10:43:28 +04:00
|
|
|
|
2021-07-21 02:56:17 +03:00
|
|
|
Resulting in this JSON object::
|
2014-06-18 10:43:28 +04:00
|
|
|
|
2021-07-21 02:56:17 +03:00
|
|
|
{ "event": "EVENT_C",
|
|
|
|
"data": { "b": "test string" },
|
|
|
|
"timestamp": { "seconds": 1267020223, "microseconds": 435656 } }
|
2011-07-19 23:50:46 +04:00
|
|
|
|
2019-09-13 23:13:48 +03:00
|
|
|
The generator emits a function to send the event. When member 'boxed'
|
|
|
|
is absent, it takes event-specific data one by one, in QAPI schema
|
|
|
|
order. Else it takes them wrapped in the C struct generated for the
|
2021-07-21 02:56:19 +03:00
|
|
|
complex type. See section `Code generated for events`_ for examples.
|
2019-09-13 23:13:48 +03:00
|
|
|
|
2021-07-21 02:56:19 +03:00
|
|
|
The optional 'if' member specifies a conditional. See `Configuring
|
|
|
|
the schema`_ below for more on this.
|
2016-07-14 06:50:20 +03:00
|
|
|
|
2021-07-21 02:56:19 +03:00
|
|
|
The optional 'features' member specifies features. See Features_
|
2020-03-17 14:54:37 +03:00
|
|
|
below for more on this.
|
|
|
|
|
2014-09-26 19:20:33 +04:00
|
|
|
|
2021-07-21 02:56:19 +03:00
|
|
|
.. _FEATURE:
|
|
|
|
|
2021-07-21 02:56:17 +03:00
|
|
|
Features
|
|
|
|
--------
|
|
|
|
|
|
|
|
Syntax::
|
2019-06-06 18:37:57 +03:00
|
|
|
|
2019-09-13 23:13:48 +03:00
|
|
|
FEATURES = [ FEATURE, ... ]
|
|
|
|
FEATURE = STRING
|
|
|
|
| { 'name': STRING, '*if': COND }
|
|
|
|
|
2019-06-06 18:37:57 +03:00
|
|
|
Sometimes, the behaviour of QEMU changes compatibly, but without a
|
2019-09-13 23:13:48 +03:00
|
|
|
change in the QMP syntax (usually by allowing values or operations
|
|
|
|
that previously resulted in an error). QMP clients may still need to
|
|
|
|
know whether the extension is available.
|
2019-06-06 18:37:57 +03:00
|
|
|
|
2023-02-13 16:20:08 +03:00
|
|
|
For this purpose, a list of features can be specified for definitions,
|
|
|
|
enumeration values, and struct members. Each feature list member can
|
|
|
|
either be ``{ 'name': STRING, '*if': COND }``, or STRING, which is
|
|
|
|
shorthand for ``{ 'name': STRING }``.
|
2019-06-06 18:37:57 +03:00
|
|
|
|
2021-07-21 02:56:19 +03:00
|
|
|
The optional 'if' member specifies a conditional. See `Configuring
|
|
|
|
the schema`_ below for more on this.
|
2019-06-06 18:37:57 +03:00
|
|
|
|
2021-07-21 02:56:17 +03:00
|
|
|
Example::
|
2019-06-06 18:37:57 +03:00
|
|
|
|
2021-07-21 02:56:17 +03:00
|
|
|
{ 'struct': 'TestType',
|
|
|
|
'data': { 'number': 'int' },
|
|
|
|
'features': [ 'allow-negative-numbers' ] }
|
2019-06-06 18:37:57 +03:00
|
|
|
|
2020-03-17 14:54:29 +03:00
|
|
|
The feature strings are exposed to clients in introspection, as
|
2021-07-21 02:56:19 +03:00
|
|
|
explained in section `Client JSON Protocol introspection`_.
|
2020-03-17 14:54:29 +03:00
|
|
|
|
|
|
|
Intended use is to have each feature string signal that this build of
|
|
|
|
QEMU shows a certain behaviour.
|
|
|
|
|
2019-06-06 18:37:57 +03:00
|
|
|
|
2021-07-21 02:56:17 +03:00
|
|
|
Special features
|
|
|
|
~~~~~~~~~~~~~~~~
|
2020-03-17 14:54:50 +03:00
|
|
|
|
2021-10-25 07:24:02 +03:00
|
|
|
Feature "deprecated" marks a command, event, enum value, or struct
|
|
|
|
member as deprecated. It is not supported elsewhere so far.
|
|
|
|
Interfaces so marked may be withdrawn in future releases in accordance
|
|
|
|
with QEMU's deprecation policy.
|
2020-03-17 14:54:50 +03:00
|
|
|
|
qapi: New special feature flag "unstable"
By convention, names starting with "x-" are experimental. The parts
of external interfaces so named may be withdrawn or changed
incompatibly in future releases.
The naming convention makes unstable interfaces easy to recognize.
Promoting something from experimental to stable involves a name
change. Client code needs to be updated. Occasionally bothersome.
Worse, the convention is not universally observed:
* QOM type "input-barrier" has properties "x-origin", "y-origin".
Looks accidental, but it's ABI since 4.2.
* QOM types "memory-backend-file", "memory-backend-memfd",
"memory-backend-ram", and "memory-backend-epc" have a property
"x-use-canonical-path-for-ramblock-id" that is documented to be
stable despite its name.
We could document these exceptions, but documentation helps only
humans. We want to recognize "unstable" in code, like "deprecated".
So support recognizing it the same way: introduce new special feature
flag "unstable". It will be treated specially by the QAPI generator,
like the existing feature flag "deprecated", and unlike regular
feature flags.
This commit updates documentation and prepares tests. The next commit
updates the QAPI schema. The remaining patches update the QAPI
generator and wire up -compat policy checking.
Management applications can then use query-qmp-schema and -compat to
manage or guard against use of unstable interfaces the same way as for
deprecated interfaces.
docs/devel/qapi-code-gen.txt no longer mandates the naming convention.
Using it anyway might help writers of programs that aren't
full-fledged management applications. Not using it can save us
bothersome renames. We'll see how that shakes out.
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Juan Quintela <quintela@redhat.com>
Reviewed-by: John Snow <jsnow@redhat.com>
Message-Id: <20211028102520.747396-2-armbru@redhat.com>
2021-10-28 13:25:12 +03:00
|
|
|
Feature "unstable" marks a command, event, enum value, or struct
|
|
|
|
member as unstable. It is not supported elsewhere so far. Interfaces
|
|
|
|
so marked may be withdrawn or changed incompatibly in future releases.
|
|
|
|
|
2020-03-17 14:54:50 +03:00
|
|
|
|
2021-07-21 02:56:17 +03:00
|
|
|
Naming rules and reserved names
|
|
|
|
-------------------------------
|
2019-09-13 23:13:45 +03:00
|
|
|
|
|
|
|
All names must begin with a letter, and contain only ASCII letters,
|
|
|
|
digits, hyphen, and underscore. There are two exceptions: enum values
|
|
|
|
may start with a digit, and names that are downstream extensions (see
|
2021-07-21 02:56:19 +03:00
|
|
|
section `Downstream extensions`_) start with underscore.
|
2019-09-13 23:13:45 +03:00
|
|
|
|
2021-07-21 02:56:18 +03:00
|
|
|
Names beginning with ``q_`` are reserved for the generator, which uses
|
2019-09-13 23:13:45 +03:00
|
|
|
them for munging QMP names that resemble C keywords or other
|
2021-07-21 02:56:18 +03:00
|
|
|
problematic strings. For example, a member named ``default`` in qapi
|
|
|
|
becomes ``q_default`` in the generated C code.
|
2019-09-13 23:13:45 +03:00
|
|
|
|
|
|
|
Types, commands, and events share a common namespace. Therefore,
|
|
|
|
generally speaking, type definitions should always use CamelCase for
|
|
|
|
user-defined type names, while built-in types are lowercase.
|
|
|
|
|
2023-12-21 17:57:27 +03:00
|
|
|
Type names ending with ``List`` are reserved for the generator, which
|
|
|
|
uses them for array types.
|
2019-09-13 23:13:45 +03:00
|
|
|
|
2022-05-10 09:16:45 +03:00
|
|
|
Command names, member names within a type, and feature names should be
|
|
|
|
all lower case with words separated by a hyphen. However, some
|
|
|
|
existing older commands and complex types use underscore; when
|
|
|
|
extending them, consistency is preferred over blindly avoiding
|
|
|
|
underscore.
|
2019-09-13 23:13:45 +03:00
|
|
|
|
|
|
|
Event names should be ALL_CAPS with words separated by underscore.
|
|
|
|
|
2021-07-21 02:56:18 +03:00
|
|
|
Member name ``u`` and names starting with ``has-`` or ``has_`` are reserved
|
2019-09-13 23:13:45 +03:00
|
|
|
for the generator, which uses them for unions and for tracking
|
|
|
|
optional members.
|
|
|
|
|
qapi: New special feature flag "unstable"
By convention, names starting with "x-" are experimental. The parts
of external interfaces so named may be withdrawn or changed
incompatibly in future releases.
The naming convention makes unstable interfaces easy to recognize.
Promoting something from experimental to stable involves a name
change. Client code needs to be updated. Occasionally bothersome.
Worse, the convention is not universally observed:
* QOM type "input-barrier" has properties "x-origin", "y-origin".
Looks accidental, but it's ABI since 4.2.
* QOM types "memory-backend-file", "memory-backend-memfd",
"memory-backend-ram", and "memory-backend-epc" have a property
"x-use-canonical-path-for-ramblock-id" that is documented to be
stable despite its name.
We could document these exceptions, but documentation helps only
humans. We want to recognize "unstable" in code, like "deprecated".
So support recognizing it the same way: introduce new special feature
flag "unstable". It will be treated specially by the QAPI generator,
like the existing feature flag "deprecated", and unlike regular
feature flags.
This commit updates documentation and prepares tests. The next commit
updates the QAPI schema. The remaining patches update the QAPI
generator and wire up -compat policy checking.
Management applications can then use query-qmp-schema and -compat to
manage or guard against use of unstable interfaces the same way as for
deprecated interfaces.
docs/devel/qapi-code-gen.txt no longer mandates the naming convention.
Using it anyway might help writers of programs that aren't
full-fledged management applications. Not using it can save us
bothersome renames. We'll see how that shakes out.
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Juan Quintela <quintela@redhat.com>
Reviewed-by: John Snow <jsnow@redhat.com>
Message-Id: <20211028102520.747396-2-armbru@redhat.com>
2021-10-28 13:25:12 +03:00
|
|
|
Names beginning with ``x-`` used to signify "experimental". This
|
|
|
|
convention has been replaced by special feature "unstable".
|
2019-09-13 23:13:45 +03:00
|
|
|
|
2021-07-21 02:56:19 +03:00
|
|
|
Pragmas ``command-name-exceptions`` and ``member-name-exceptions`` let
|
|
|
|
you violate naming rules. Use for new code is strongly discouraged. See
|
|
|
|
`Pragma directives`_ for details.
|
2019-09-13 23:13:45 +03:00
|
|
|
|
|
|
|
|
2021-07-21 02:56:17 +03:00
|
|
|
Downstream extensions
|
|
|
|
---------------------
|
2017-03-01 00:27:09 +03:00
|
|
|
|
|
|
|
QAPI schema names that are externally visible, say in the Client JSON
|
|
|
|
Protocol, need to be managed with care. Names starting with a
|
|
|
|
downstream prefix of the form __RFQDN_ are reserved for the downstream
|
|
|
|
who controls the valid, reverse fully qualified domain name RFQDN.
|
|
|
|
RFQDN may only contain ASCII letters, digits, hyphen and period.
|
|
|
|
|
|
|
|
Example: Red Hat, Inc. controls redhat.com, and may therefore add a
|
2021-07-21 02:56:18 +03:00
|
|
|
downstream command ``__com.redhat_drive-mirror``.
|
2017-03-01 00:27:09 +03:00
|
|
|
|
|
|
|
|
2021-07-21 02:56:17 +03:00
|
|
|
Configuring the schema
|
|
|
|
----------------------
|
|
|
|
|
|
|
|
Syntax::
|
2018-07-03 18:56:35 +03:00
|
|
|
|
2019-09-13 23:13:48 +03:00
|
|
|
COND = STRING
|
2021-08-04 11:30:56 +03:00
|
|
|
| { 'all: [ COND, ... ] }
|
|
|
|
| { 'any: [ COND, ... ] }
|
|
|
|
| { 'not': COND }
|
2019-09-13 23:13:48 +03:00
|
|
|
|
|
|
|
All definitions take an optional 'if' member. Its value must be a
|
2021-08-04 11:30:56 +03:00
|
|
|
string, or an object with a single member 'all', 'any' or 'not'.
|
|
|
|
|
|
|
|
The C code generated for the definition will then be guarded by an #if
|
|
|
|
preprocessing directive with an operand generated from that condition:
|
|
|
|
|
|
|
|
* STRING will generate defined(STRING)
|
|
|
|
* { 'all': [COND, ...] } will generate (COND && ...)
|
|
|
|
* { 'any': [COND, ...] } will generate (COND || ...)
|
|
|
|
* { 'not': COND } will generate !COND
|
2018-07-03 18:56:35 +03:00
|
|
|
|
2021-07-21 02:56:17 +03:00
|
|
|
Example: a conditional struct ::
|
2018-07-03 18:56:35 +03:00
|
|
|
|
|
|
|
{ 'struct': 'IfStruct', 'data': { 'foo': 'int' },
|
2021-08-04 11:30:56 +03:00
|
|
|
'if': { 'all': [ 'CONFIG_FOO', 'HAVE_BAR' ] } }
|
2018-07-03 18:56:35 +03:00
|
|
|
|
2021-07-21 02:56:17 +03:00
|
|
|
gets its generated code guarded like this::
|
2018-07-03 18:56:35 +03:00
|
|
|
|
2021-08-04 11:30:56 +03:00
|
|
|
#if defined(CONFIG_FOO) && defined(HAVE_BAR)
|
2018-07-03 18:56:35 +03:00
|
|
|
... generated code ...
|
2021-08-04 11:30:56 +03:00
|
|
|
#endif /* defined(HAVE_BAR) && defined(CONFIG_FOO) */
|
2018-07-03 18:56:35 +03:00
|
|
|
|
2023-03-16 10:13:25 +03:00
|
|
|
Individual members of complex types can also be made conditional.
|
|
|
|
This requires the longhand form of MEMBER.
|
2018-12-13 15:37:15 +03:00
|
|
|
|
2019-09-13 23:13:48 +03:00
|
|
|
Example: a struct type with unconditional member 'foo' and conditional
|
2021-07-21 02:56:17 +03:00
|
|
|
member 'bar' ::
|
2018-12-13 15:37:15 +03:00
|
|
|
|
2021-09-17 17:31:12 +03:00
|
|
|
{ 'struct': 'IfStruct',
|
|
|
|
'data': { 'foo': 'int',
|
|
|
|
'bar': { 'type': 'int', 'if': 'IFCOND'} } }
|
2018-12-13 15:37:15 +03:00
|
|
|
|
2019-09-13 23:13:48 +03:00
|
|
|
A union's discriminator may not be conditional.
|
2018-12-13 15:37:11 +03:00
|
|
|
|
2023-02-13 16:20:09 +03:00
|
|
|
Likewise, individual enumeration values may be conditional. This
|
|
|
|
requires the longhand form of ENUM-VALUE_.
|
2019-09-13 23:13:48 +03:00
|
|
|
|
|
|
|
Example: an enum type with unconditional value 'foo' and conditional
|
2021-07-21 02:56:17 +03:00
|
|
|
value 'bar' ::
|
2018-12-13 15:37:11 +03:00
|
|
|
|
2021-09-17 17:31:12 +03:00
|
|
|
{ 'enum': 'IfEnum',
|
|
|
|
'data': [ 'foo',
|
|
|
|
{ 'name' : 'bar', 'if': 'IFCOND' } ] }
|
2018-12-13 15:37:11 +03:00
|
|
|
|
2019-09-13 23:13:48 +03:00
|
|
|
Likewise, features can be conditional. This requires the longhand
|
2021-07-21 02:56:19 +03:00
|
|
|
form of FEATURE_.
|
2019-06-06 18:37:57 +03:00
|
|
|
|
2021-07-21 02:56:17 +03:00
|
|
|
Example: a struct with conditional feature 'allow-negative-numbers' ::
|
2019-06-06 18:37:57 +03:00
|
|
|
|
2021-07-21 02:56:17 +03:00
|
|
|
{ 'struct': 'TestType',
|
|
|
|
'data': { 'number': 'int' },
|
|
|
|
'features': [ { 'name': 'allow-negative-numbers',
|
2021-08-04 11:30:56 +03:00
|
|
|
'if': 'IFCOND' } ] }
|
2019-06-06 18:37:57 +03:00
|
|
|
|
2018-07-03 18:56:35 +03:00
|
|
|
Please note that you are responsible to ensure that the C code will
|
|
|
|
compile with an arbitrary combination of conditions, since the
|
2019-09-13 23:13:48 +03:00
|
|
|
generator is unable to check it at this point.
|
2018-07-03 18:56:35 +03:00
|
|
|
|
2019-09-13 23:13:48 +03:00
|
|
|
The conditions apply to introspection as well, i.e. introspection
|
|
|
|
shows a conditional entity only when the condition is satisfied in
|
|
|
|
this particular build.
|
2018-07-03 18:56:35 +03:00
|
|
|
|
|
|
|
|
2021-07-21 02:56:17 +03:00
|
|
|
Documentation comments
|
|
|
|
----------------------
|
2019-09-13 23:13:45 +03:00
|
|
|
|
2021-07-21 02:56:18 +03:00
|
|
|
A multi-line comment that starts and ends with a ``##`` line is a
|
2019-09-13 23:13:48 +03:00
|
|
|
documentation comment.
|
|
|
|
|
2021-07-21 02:56:17 +03:00
|
|
|
If the documentation comment starts like ::
|
2019-09-13 23:13:48 +03:00
|
|
|
|
|
|
|
##
|
|
|
|
# @SYMBOL:
|
|
|
|
|
2021-07-21 02:56:18 +03:00
|
|
|
it documents the definition of SYMBOL, else it's free-form
|
2019-09-13 23:13:48 +03:00
|
|
|
documentation.
|
|
|
|
|
2021-07-21 02:56:19 +03:00
|
|
|
See below for more on `Definition documentation`_.
|
2019-09-13 23:13:48 +03:00
|
|
|
|
|
|
|
Free-form documentation may be used to provide additional text and
|
|
|
|
structuring content.
|
2019-09-13 23:13:45 +03:00
|
|
|
|
2021-07-21 02:56:17 +03:00
|
|
|
|
|
|
|
Headings and subheadings
|
|
|
|
~~~~~~~~~~~~~~~~~~~~~~~~
|
2019-09-13 23:13:45 +03:00
|
|
|
|
2020-09-25 19:23:12 +03:00
|
|
|
A free-form documentation comment containing a line which starts with
|
2021-07-21 02:56:18 +03:00
|
|
|
some ``=`` symbols and then a space defines a section heading::
|
2019-09-13 23:13:45 +03:00
|
|
|
|
2020-09-25 19:23:12 +03:00
|
|
|
##
|
|
|
|
# = This is a top level heading
|
|
|
|
#
|
|
|
|
# This is a free-form comment which will go under the
|
|
|
|
# top level heading.
|
|
|
|
##
|
2019-09-13 23:13:45 +03:00
|
|
|
|
2020-09-25 19:23:12 +03:00
|
|
|
##
|
|
|
|
# == This is a second level heading
|
|
|
|
##
|
2019-09-13 23:13:45 +03:00
|
|
|
|
2020-09-25 19:23:12 +03:00
|
|
|
A heading line must be the first line of the documentation
|
|
|
|
comment block.
|
2019-09-13 23:13:45 +03:00
|
|
|
|
2020-09-25 19:23:12 +03:00
|
|
|
Section headings must always be correctly nested, so you can only
|
|
|
|
define a third-level heading inside a second-level heading, and so on.
|
2019-09-13 23:13:45 +03:00
|
|
|
|
2021-07-21 02:56:17 +03:00
|
|
|
|
|
|
|
Documentation markup
|
|
|
|
~~~~~~~~~~~~~~~~~~~~
|
2020-03-20 12:18:04 +03:00
|
|
|
|
2020-09-25 19:23:12 +03:00
|
|
|
Documentation comments can use most rST markup. In particular,
|
2021-07-21 02:56:18 +03:00
|
|
|
a ``::`` literal block can be used for examples::
|
2019-09-13 23:13:45 +03:00
|
|
|
|
2020-09-25 19:23:12 +03:00
|
|
|
# ::
|
|
|
|
#
|
|
|
|
# Text of the example, may span
|
|
|
|
# multiple lines
|
2019-09-13 23:13:45 +03:00
|
|
|
|
2021-07-21 02:56:18 +03:00
|
|
|
``*`` starts an itemized list::
|
2019-09-13 23:13:45 +03:00
|
|
|
|
|
|
|
# * First item, may span
|
|
|
|
# multiple lines
|
|
|
|
# * Second item
|
|
|
|
|
2021-07-21 02:56:18 +03:00
|
|
|
You can also use ``-`` instead of ``*``.
|
2019-09-13 23:13:45 +03:00
|
|
|
|
2021-07-21 02:56:18 +03:00
|
|
|
A decimal number followed by ``.`` starts a numbered list::
|
2019-09-13 23:13:45 +03:00
|
|
|
|
|
|
|
# 1. First item, may span
|
|
|
|
# multiple lines
|
|
|
|
# 2. Second item
|
|
|
|
|
2020-09-25 19:23:12 +03:00
|
|
|
The actual number doesn't matter.
|
2019-09-13 23:13:45 +03:00
|
|
|
|
2020-09-25 19:23:12 +03:00
|
|
|
Lists of either kind must be preceded and followed by a blank line.
|
|
|
|
If a list item's text spans multiple lines, then the second and
|
|
|
|
subsequent lines must be correctly indented to line up with the
|
|
|
|
first character of the first line.
|
2019-09-13 23:13:45 +03:00
|
|
|
|
2021-07-21 02:56:18 +03:00
|
|
|
The usual ****strong****, *\*emphasized\** and ````literal```` markup
|
|
|
|
should be used. If you need a single literal ``*``, you will need to
|
2023-04-25 09:42:13 +03:00
|
|
|
backslash-escape it.
|
|
|
|
|
|
|
|
Use ``@foo`` to reference a name in the schema. This is an rST
|
|
|
|
extension. It is rendered the same way as ````foo````, but carries
|
|
|
|
additional meaning.
|
2019-09-13 23:13:45 +03:00
|
|
|
|
2021-07-21 02:56:17 +03:00
|
|
|
Example::
|
2019-09-13 23:13:45 +03:00
|
|
|
|
2021-07-21 02:56:17 +03:00
|
|
|
##
|
|
|
|
# Some text foo with **bold** and *emphasis*
|
2023-04-25 09:42:16 +03:00
|
|
|
#
|
2021-07-21 02:56:17 +03:00
|
|
|
# 1. with a list
|
|
|
|
# 2. like that
|
|
|
|
#
|
|
|
|
# And some code:
|
|
|
|
#
|
|
|
|
# ::
|
|
|
|
#
|
|
|
|
# $ echo foo
|
|
|
|
# -> do this
|
|
|
|
# <- get that
|
|
|
|
##
|
2019-09-13 23:13:45 +03:00
|
|
|
|
2023-04-28 13:54:27 +03:00
|
|
|
For legibility, wrap text paragraphs so every line is at most 70
|
|
|
|
characters long.
|
|
|
|
|
|
|
|
Separate sentences with two spaces.
|
|
|
|
|
2019-09-13 23:13:45 +03:00
|
|
|
|
2021-07-21 02:56:17 +03:00
|
|
|
Definition documentation
|
|
|
|
~~~~~~~~~~~~~~~~~~~~~~~~
|
2019-09-13 23:13:45 +03:00
|
|
|
|
2019-09-13 23:13:48 +03:00
|
|
|
Definition documentation, if present, must immediately precede the
|
|
|
|
definition it documents.
|
2019-09-13 23:13:45 +03:00
|
|
|
|
2021-07-21 02:56:19 +03:00
|
|
|
When documentation is required (see pragma_ 'doc-required'), every
|
2019-09-13 23:13:48 +03:00
|
|
|
definition must have documentation.
|
2019-09-13 23:13:45 +03:00
|
|
|
|
2019-09-13 23:13:48 +03:00
|
|
|
Definition documentation starts with a line naming the definition,
|
|
|
|
followed by an optional overview, a description of each argument (for
|
|
|
|
commands and events), member (for structs and unions), branch (for
|
2021-10-26 14:10:23 +03:00
|
|
|
alternates), or value (for enums), a description of each feature (if
|
|
|
|
any), and finally optional tagged sections.
|
2019-09-13 23:13:45 +03:00
|
|
|
|
2023-04-28 13:54:27 +03:00
|
|
|
Descriptions start with '\@name:'. The description text should be
|
|
|
|
indented like this::
|
|
|
|
|
|
|
|
# @name: Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed
|
|
|
|
# do eiusmod tempor incididunt ut labore et dolore magna aliqua.
|
2020-09-25 19:23:00 +03:00
|
|
|
|
2023-04-28 13:54:14 +03:00
|
|
|
.. FIXME The parser accepts these things in almost any order.
|
2020-09-25 19:23:00 +03:00
|
|
|
|
2023-04-28 13:54:14 +03:00
|
|
|
.. FIXME union branches should be described, too.
|
2019-09-13 23:13:45 +03:00
|
|
|
|
2019-09-13 23:13:48 +03:00
|
|
|
Extensions added after the definition was first released carry a
|
2023-04-28 13:54:13 +03:00
|
|
|
"(since x.y.z)" comment.
|
2019-09-13 23:13:45 +03:00
|
|
|
|
2021-10-26 14:10:23 +03:00
|
|
|
The feature descriptions must be preceded by a line "Features:", like
|
|
|
|
this::
|
|
|
|
|
|
|
|
# Features:
|
2023-04-28 13:54:27 +03:00
|
|
|
#
|
2021-10-26 14:10:23 +03:00
|
|
|
# @feature: Description text
|
|
|
|
|
2019-09-13 23:13:45 +03:00
|
|
|
A tagged section starts with one of the following words:
|
2024-01-20 12:53:21 +03:00
|
|
|
"Note:"/"Notes:", "Since:", "Example:"/"Examples:", "Returns:",
|
|
|
|
"TODO:". The section ends with the start of a new section.
|
2019-09-13 23:13:45 +03:00
|
|
|
|
2023-04-28 13:54:27 +03:00
|
|
|
The second and subsequent lines of sections other than
|
|
|
|
"Example"/"Examples" should be indented like this::
|
|
|
|
|
|
|
|
# Note: Ut enim ad minim veniam, quis nostrud exercitation ullamco
|
|
|
|
# laboris nisi ut aliquip ex ea commodo consequat.
|
|
|
|
#
|
|
|
|
# Duis aute irure dolor in reprehenderit in voluptate velit esse
|
|
|
|
# cillum dolore eu fugiat nulla pariatur.
|
2020-09-25 19:23:00 +03:00
|
|
|
|
2023-04-28 13:54:13 +03:00
|
|
|
A "Since: x.y.z" tagged section lists the release that introduced the
|
2019-09-13 23:13:48 +03:00
|
|
|
definition.
|
2019-09-13 23:13:45 +03:00
|
|
|
|
2023-04-28 13:54:27 +03:00
|
|
|
An "Example" or "Examples" section is rendered entirely
|
2023-04-28 13:54:18 +03:00
|
|
|
as literal fixed-width text. "TODO" sections are not rendered at all
|
|
|
|
(they are for developers, not users of QMP). In other sections, the
|
|
|
|
text is formatted, and rST markup can be used.
|
2020-09-25 19:23:12 +03:00
|
|
|
|
2021-07-21 02:56:17 +03:00
|
|
|
For example::
|
|
|
|
|
|
|
|
##
|
|
|
|
# @BlockStats:
|
|
|
|
#
|
|
|
|
# Statistics of a virtual block device or a block backing device.
|
|
|
|
#
|
|
|
|
# @device: If the stats are for a virtual block device, the name
|
2023-04-28 13:54:27 +03:00
|
|
|
# corresponding to the virtual block device.
|
2021-07-21 02:56:17 +03:00
|
|
|
#
|
|
|
|
# @node-name: The node name of the device. (since 2.3)
|
|
|
|
#
|
|
|
|
# ... more members ...
|
|
|
|
#
|
2024-02-05 10:46:55 +03:00
|
|
|
# Since: 0.14
|
2021-07-21 02:56:17 +03:00
|
|
|
##
|
|
|
|
{ 'struct': 'BlockStats',
|
|
|
|
'data': {'*device': 'str', '*node-name': 'str',
|
|
|
|
... more members ... } }
|
|
|
|
|
|
|
|
##
|
|
|
|
# @query-blockstats:
|
|
|
|
#
|
|
|
|
# Query the @BlockStats for all virtual block devices.
|
|
|
|
#
|
2023-04-28 13:54:27 +03:00
|
|
|
# @query-nodes: If true, the command will query all the block nodes
|
|
|
|
# ... explain, explain ... (since 2.3)
|
2021-07-21 02:56:17 +03:00
|
|
|
#
|
|
|
|
# Returns: A list of @BlockStats for each virtual block devices.
|
|
|
|
#
|
2024-02-05 10:46:55 +03:00
|
|
|
# Since: 0.14
|
2021-07-21 02:56:17 +03:00
|
|
|
#
|
|
|
|
# Example:
|
|
|
|
#
|
|
|
|
# -> { "execute": "query-blockstats" }
|
|
|
|
# <- {
|
|
|
|
# ... lots of output ...
|
|
|
|
# }
|
|
|
|
#
|
|
|
|
##
|
|
|
|
{ 'command': 'query-blockstats',
|
|
|
|
'data': { '*query-nodes': 'bool' },
|
|
|
|
'returns': ['BlockStats'] }
|
|
|
|
|
|
|
|
|
2023-04-27 12:53:45 +03:00
|
|
|
Markup pitfalls
|
|
|
|
~~~~~~~~~~~~~~~
|
|
|
|
|
|
|
|
A blank line is required between list items and paragraphs. Without
|
|
|
|
it, the list may not be recognized, resulting in garbled output. Good
|
|
|
|
example::
|
|
|
|
|
|
|
|
# An event's state is modified if:
|
|
|
|
#
|
|
|
|
# - its name matches the @name pattern, and
|
|
|
|
# - if @vcpu is given, the event has the "vcpu" property.
|
|
|
|
|
|
|
|
Without the blank line this would be a single paragraph.
|
|
|
|
|
|
|
|
Indentation matters. Bad example::
|
|
|
|
|
|
|
|
# @none: None (no memory side cache in this proximity domain,
|
|
|
|
# or cache associativity unknown)
|
qapi: Relax doc string @name: description indentation rules
The QAPI schema doc comment language provides special syntax for
command and event arguments, struct and union members, alternate
branches, enumeration values, and features: descriptions starting with
"@name:".
By convention, we format them like this:
# @name: Lorem ipsum dolor sit amet, consectetur adipiscing elit,
# sed do eiusmod tempor incididunt ut labore et dolore
# magna aliqua.
Okay for names as short as "name", but we have much longer ones. Their
description gets squeezed against the right margin, like this:
# @dirty-sync-missed-zero-copy: Number of times dirty RAM synchronization could
# not avoid copying dirty pages. This is between
# 0 and @dirty-sync-count * @multifd-channels.
# (since 7.1)
The description text is effectively just 50 characters wide. Easy
enough to read, but can be cumbersome to write.
The awkward squeeze against the right margin makes people go beyond it,
which produces two undesirables: arguments about style, and descriptions
that are unnecessarily hard to read, like this one:
# @postcopy-vcpu-blocktime: list of the postcopy blocktime per vCPU. This is
# only present when the postcopy-blocktime migration capability
# is enabled. (Since 3.0)
We could instead format it like
# @postcopy-vcpu-blocktime:
# list of the postcopy blocktime per vCPU. This is only present
# when the postcopy-blocktime migration capability is
# enabled. (Since 3.0)
or, since the commit before previous, like
# @postcopy-vcpu-blocktime:
# list of the postcopy blocktime per vCPU. This is only present
# when the postcopy-blocktime migration capability is
# enabled. (Since 3.0)
However, I'd rather have
# @postcopy-vcpu-blocktime: list of the postcopy blocktime per vCPU.
# This is only present when the postcopy-blocktime migration
# capability is enabled. (Since 3.0)
because this is how rST field and option lists work.
To get this, we need to let the first non-blank line after the
"@name:" line determine expected indentation.
This fills up the indentation pitfall mentioned in
docs/devel/qapi-code-gen.rst. A related pitfall still exists. Update
the text to show it.
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Message-Id: <20230428105429.1687850-14-armbru@redhat.com>
Reviewed-by: Juan Quintela <quintela@redhat.com>
[Work around lack of walrus operator in Python 3.7 and older]
2023-04-28 13:54:25 +03:00
|
|
|
# (since 5.0)
|
2023-04-27 12:53:45 +03:00
|
|
|
|
qapi: Relax doc string @name: description indentation rules
The QAPI schema doc comment language provides special syntax for
command and event arguments, struct and union members, alternate
branches, enumeration values, and features: descriptions starting with
"@name:".
By convention, we format them like this:
# @name: Lorem ipsum dolor sit amet, consectetur adipiscing elit,
# sed do eiusmod tempor incididunt ut labore et dolore
# magna aliqua.
Okay for names as short as "name", but we have much longer ones. Their
description gets squeezed against the right margin, like this:
# @dirty-sync-missed-zero-copy: Number of times dirty RAM synchronization could
# not avoid copying dirty pages. This is between
# 0 and @dirty-sync-count * @multifd-channels.
# (since 7.1)
The description text is effectively just 50 characters wide. Easy
enough to read, but can be cumbersome to write.
The awkward squeeze against the right margin makes people go beyond it,
which produces two undesirables: arguments about style, and descriptions
that are unnecessarily hard to read, like this one:
# @postcopy-vcpu-blocktime: list of the postcopy blocktime per vCPU. This is
# only present when the postcopy-blocktime migration capability
# is enabled. (Since 3.0)
We could instead format it like
# @postcopy-vcpu-blocktime:
# list of the postcopy blocktime per vCPU. This is only present
# when the postcopy-blocktime migration capability is
# enabled. (Since 3.0)
or, since the commit before previous, like
# @postcopy-vcpu-blocktime:
# list of the postcopy blocktime per vCPU. This is only present
# when the postcopy-blocktime migration capability is
# enabled. (Since 3.0)
However, I'd rather have
# @postcopy-vcpu-blocktime: list of the postcopy blocktime per vCPU.
# This is only present when the postcopy-blocktime migration
# capability is enabled. (Since 3.0)
because this is how rST field and option lists work.
To get this, we need to let the first non-blank line after the
"@name:" line determine expected indentation.
This fills up the indentation pitfall mentioned in
docs/devel/qapi-code-gen.rst. A related pitfall still exists. Update
the text to show it.
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Message-Id: <20230428105429.1687850-14-armbru@redhat.com>
Reviewed-by: Juan Quintela <quintela@redhat.com>
[Work around lack of walrus operator in Python 3.7 and older]
2023-04-28 13:54:25 +03:00
|
|
|
The last line's de-indent is wrong. The second and subsequent lines
|
|
|
|
need to line up with each other, like this::
|
|
|
|
|
|
|
|
# @none: None (no memory side cache in this proximity domain,
|
|
|
|
# or cache associativity unknown)
|
|
|
|
# (since 5.0)
|
2023-04-27 12:53:45 +03:00
|
|
|
|
|
|
|
Section tags are case-sensitive and end with a colon. Good example::
|
|
|
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|
|
# Since: 7.1
|
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|
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|
|
|
Bad examples (all ordinary paragraphs)::
|
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|
|
# since: 7.1
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|
# Since 7.1
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|
# Since : 7.1
|
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Likewise, member descriptions require a colon. Good example::
|
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|
# @interface-id: Interface ID
|
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|
|
Bad examples (all ordinary paragraphs)::
|
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|
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|
|
# @interface-id Interface ID
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|
# @interface-id : Interface ID
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Undocumented members are not flagged, yet. Instead, the generated
|
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|
|
documentation describes them as "Not documented". Think twice before
|
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|
adding more undocumented members.
|
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|
When you change documentation comments, please check the generated
|
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|
documentation comes out as intended!
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|
2021-07-21 02:56:17 +03:00
|
|
|
Client JSON Protocol introspection
|
|
|
|
==================================
|
qapi: New QMP command query-qmp-schema for QMP introspection
qapi/introspect.json defines the introspection schema. It's designed
for QMP introspection, but should do for similar uses, such as QGA.
The introspection schema does not reflect all the rules and
restrictions that apply to QAPI schemata. A valid QAPI schema has an
introspection value conforming to the introspection schema, but the
converse is not true.
Introspection lowers away a number of schema details, and makes
implicit things explicit:
* The built-in types are declared with their JSON type.
All integer types are mapped to 'int', because how many bits we use
internally is an implementation detail. It could be pressed into
external interface service as very approximate range information,
but that's a bad idea. If we need range information, we better do
it properly.
* Implicit type definitions are made explicit, and given
auto-generated names:
- Array types, named by appending "List" to the name of their
element type, like in generated C.
- The enumeration types implicitly defined by simple union types,
named by appending "Kind" to the name of their simple union type,
like in generated C.
- Types that don't occur in generated C. Their names start with ':'
so they don't clash with the user's names.
* All type references are by name.
* The struct and union types are generalized into an object type.
* Base types are flattened.
* Commands take a single argument and return a single result.
Dictionary argument or list result is an implicit type definition.
The empty object type is used when a command takes no arguments or
produces no results.
The argument is always of object type, but the introspection schema
doesn't reflect that.
The 'gen': false directive is omitted as implementation detail.
The 'success-response' directive is omitted as well for now, even
though it's not an implementation detail, because it's not used by
QMP.
* Events carry a single data value.
Implicit type definition and empty object type use, just like for
commands.
The value is of object type, but the introspection schema doesn't
reflect that.
* Types not used by commands or events are omitted.
Indirect use counts as use.
* Optional members have a default, which can only be null right now
Instead of a mandatory "optional" flag, we have an optional default.
No default means mandatory, default null means optional without
default value. Non-null is available for optional with default
(possible future extension).
* Clients should *not* look up types by name, because type names are
not ABI. Look up the command or event you're interested in, then
follow the references.
TODO Should we hide the type names to eliminate the temptation?
New generator scripts/qapi-introspect.py computes an introspection
value for its input, and generates a C variable holding it.
It can generate awfully long lines. Marked TODO.
A new test-qmp-input-visitor test case feeds its result for both
tests/qapi-schema/qapi-schema-test.json and qapi-schema.json to a
QmpInputVisitor to verify it actually conforms to the schema.
New QMP command query-qmp-schema takes its return value from that
variable. Its reply is some 85KiBytes for me right now.
If this turns out to be too much, we have a couple of options:
* We can use shorter names in the JSON. Not the QMP style.
* Optionally return the sub-schema for commands and events given as
arguments.
Right now qmp_query_schema() sends the string literal computed by
qmp-introspect.py. To compute sub-schema at run time, we'd have to
duplicate parts of qapi-introspect.py in C. Unattractive.
* Let clients cache the output of query-qmp-schema.
It changes only on QEMU upgrades, i.e. rarely. Provide a command
query-qmp-schema-hash. Clients can have a cache indexed by hash,
and re-query the schema only when they don't have it cached. Even
simpler: put the hash in the QMP greeting.
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
2015-09-16 14:06:28 +03:00
|
|
|
|
|
|
|
Clients of a Client JSON Protocol commonly need to figure out what
|
|
|
|
exactly the server (QEMU) supports.
|
|
|
|
|
|
|
|
For this purpose, QMP provides introspection via command
|
|
|
|
query-qmp-schema. QGA currently doesn't support introspection.
|
|
|
|
|
2015-11-11 20:50:02 +03:00
|
|
|
While Client JSON Protocol wire compatibility should be maintained
|
|
|
|
between qemu versions, we cannot make the same guarantees for
|
|
|
|
introspection stability. For example, one version of qemu may provide
|
|
|
|
a non-variant optional member of a struct, and a later version rework
|
|
|
|
the member to instead be non-optional and associated with a variant.
|
|
|
|
Likewise, one version of qemu may list a member with open-ended type
|
|
|
|
'str', and a later version could convert it to a finite set of strings
|
|
|
|
via an enum type; or a member may be converted from a specific type to
|
|
|
|
an alternate that represents a choice between the original type and
|
|
|
|
something else.
|
|
|
|
|
qapi: New QMP command query-qmp-schema for QMP introspection
qapi/introspect.json defines the introspection schema. It's designed
for QMP introspection, but should do for similar uses, such as QGA.
The introspection schema does not reflect all the rules and
restrictions that apply to QAPI schemata. A valid QAPI schema has an
introspection value conforming to the introspection schema, but the
converse is not true.
Introspection lowers away a number of schema details, and makes
implicit things explicit:
* The built-in types are declared with their JSON type.
All integer types are mapped to 'int', because how many bits we use
internally is an implementation detail. It could be pressed into
external interface service as very approximate range information,
but that's a bad idea. If we need range information, we better do
it properly.
* Implicit type definitions are made explicit, and given
auto-generated names:
- Array types, named by appending "List" to the name of their
element type, like in generated C.
- The enumeration types implicitly defined by simple union types,
named by appending "Kind" to the name of their simple union type,
like in generated C.
- Types that don't occur in generated C. Their names start with ':'
so they don't clash with the user's names.
* All type references are by name.
* The struct and union types are generalized into an object type.
* Base types are flattened.
* Commands take a single argument and return a single result.
Dictionary argument or list result is an implicit type definition.
The empty object type is used when a command takes no arguments or
produces no results.
The argument is always of object type, but the introspection schema
doesn't reflect that.
The 'gen': false directive is omitted as implementation detail.
The 'success-response' directive is omitted as well for now, even
though it's not an implementation detail, because it's not used by
QMP.
* Events carry a single data value.
Implicit type definition and empty object type use, just like for
commands.
The value is of object type, but the introspection schema doesn't
reflect that.
* Types not used by commands or events are omitted.
Indirect use counts as use.
* Optional members have a default, which can only be null right now
Instead of a mandatory "optional" flag, we have an optional default.
No default means mandatory, default null means optional without
default value. Non-null is available for optional with default
(possible future extension).
* Clients should *not* look up types by name, because type names are
not ABI. Look up the command or event you're interested in, then
follow the references.
TODO Should we hide the type names to eliminate the temptation?
New generator scripts/qapi-introspect.py computes an introspection
value for its input, and generates a C variable holding it.
It can generate awfully long lines. Marked TODO.
A new test-qmp-input-visitor test case feeds its result for both
tests/qapi-schema/qapi-schema-test.json and qapi-schema.json to a
QmpInputVisitor to verify it actually conforms to the schema.
New QMP command query-qmp-schema takes its return value from that
variable. Its reply is some 85KiBytes for me right now.
If this turns out to be too much, we have a couple of options:
* We can use shorter names in the JSON. Not the QMP style.
* Optionally return the sub-schema for commands and events given as
arguments.
Right now qmp_query_schema() sends the string literal computed by
qmp-introspect.py. To compute sub-schema at run time, we'd have to
duplicate parts of qapi-introspect.py in C. Unattractive.
* Let clients cache the output of query-qmp-schema.
It changes only on QEMU upgrades, i.e. rarely. Provide a command
query-qmp-schema-hash. Clients can have a cache indexed by hash,
and re-query the schema only when they don't have it cached. Even
simpler: put the hash in the QMP greeting.
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
2015-09-16 14:06:28 +03:00
|
|
|
query-qmp-schema returns a JSON array of SchemaInfo objects. These
|
|
|
|
objects together describe the wire ABI, as defined in the QAPI schema.
|
qapi-introspect: Document lack of sorting
qapi-code-gen.txt already claims that types, commands, and
events share a common namespace; set this in stone by further
documenting that our introspection output will never have
collisions with the same name tied to more than one meta-type.
Our largest QMP enum currently has 125 values, our largest
object type has 27 members, and the mean for each is less than
10. These sizes are small enough that the per-element overhead
of O(log n) binary searching probably outweighs the speed
possible with direct O(n) linear searching (a better algorithm
with more overhead will only beat a leaner naive algorithm only
as you scale to larger input sizes).
Arguably, the overall SchemaInfo array could be sorted by name;
there, we currently have 531 entities, large enough for a binary
search to be faster than linear. However, remember that we have
mutually-recursive types, which means there is no topological
ordering that will allow clients to learn all information about
that type in a single linear pass; thus clients will want to do
random access over the data, and they will probably read the
introspection output into a hashtable for O(1) lookup rather
than O(log n) binary searching, at which point, pre-sorting our
introspection output doesn't help the client.
It doesn't help that sorting can be subjective if you introduce
locales into the mix (I'm not experienced enough with Python
to know for sure, but at least it looks like it defaults to
sorting in the C locale even when run under a different locale).
And while our current introspection output is deterministic
(because we visit entities in a sorted order), we may want
to change that order in the future (such as using OrderedDict
to stick to .json declaration order).
For these reasons, we simply document that clients should not
rely on any particular order of items in introspection output.
And since it is now a documented part of the contract, we have
the freedom to later rearrange output if needed, without
worrying about breaking well-written clients.
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <1446791754-23823-13-git-send-email-eblake@redhat.com>
[Commit message tweaked]
Signed-off-by: Markus Armbruster <armbru@redhat.com>
2015-11-06 09:35:36 +03:00
|
|
|
There is no specified order to the SchemaInfo objects returned; a
|
|
|
|
client must search for a particular name throughout the entire array
|
|
|
|
to learn more about that name, but is at least guaranteed that there
|
|
|
|
will be no collisions between type, command, and event names.
|
qapi: New QMP command query-qmp-schema for QMP introspection
qapi/introspect.json defines the introspection schema. It's designed
for QMP introspection, but should do for similar uses, such as QGA.
The introspection schema does not reflect all the rules and
restrictions that apply to QAPI schemata. A valid QAPI schema has an
introspection value conforming to the introspection schema, but the
converse is not true.
Introspection lowers away a number of schema details, and makes
implicit things explicit:
* The built-in types are declared with their JSON type.
All integer types are mapped to 'int', because how many bits we use
internally is an implementation detail. It could be pressed into
external interface service as very approximate range information,
but that's a bad idea. If we need range information, we better do
it properly.
* Implicit type definitions are made explicit, and given
auto-generated names:
- Array types, named by appending "List" to the name of their
element type, like in generated C.
- The enumeration types implicitly defined by simple union types,
named by appending "Kind" to the name of their simple union type,
like in generated C.
- Types that don't occur in generated C. Their names start with ':'
so they don't clash with the user's names.
* All type references are by name.
* The struct and union types are generalized into an object type.
* Base types are flattened.
* Commands take a single argument and return a single result.
Dictionary argument or list result is an implicit type definition.
The empty object type is used when a command takes no arguments or
produces no results.
The argument is always of object type, but the introspection schema
doesn't reflect that.
The 'gen': false directive is omitted as implementation detail.
The 'success-response' directive is omitted as well for now, even
though it's not an implementation detail, because it's not used by
QMP.
* Events carry a single data value.
Implicit type definition and empty object type use, just like for
commands.
The value is of object type, but the introspection schema doesn't
reflect that.
* Types not used by commands or events are omitted.
Indirect use counts as use.
* Optional members have a default, which can only be null right now
Instead of a mandatory "optional" flag, we have an optional default.
No default means mandatory, default null means optional without
default value. Non-null is available for optional with default
(possible future extension).
* Clients should *not* look up types by name, because type names are
not ABI. Look up the command or event you're interested in, then
follow the references.
TODO Should we hide the type names to eliminate the temptation?
New generator scripts/qapi-introspect.py computes an introspection
value for its input, and generates a C variable holding it.
It can generate awfully long lines. Marked TODO.
A new test-qmp-input-visitor test case feeds its result for both
tests/qapi-schema/qapi-schema-test.json and qapi-schema.json to a
QmpInputVisitor to verify it actually conforms to the schema.
New QMP command query-qmp-schema takes its return value from that
variable. Its reply is some 85KiBytes for me right now.
If this turns out to be too much, we have a couple of options:
* We can use shorter names in the JSON. Not the QMP style.
* Optionally return the sub-schema for commands and events given as
arguments.
Right now qmp_query_schema() sends the string literal computed by
qmp-introspect.py. To compute sub-schema at run time, we'd have to
duplicate parts of qapi-introspect.py in C. Unattractive.
* Let clients cache the output of query-qmp-schema.
It changes only on QEMU upgrades, i.e. rarely. Provide a command
query-qmp-schema-hash. Clients can have a cache indexed by hash,
and re-query the schema only when they don't have it cached. Even
simpler: put the hash in the QMP greeting.
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
2015-09-16 14:06:28 +03:00
|
|
|
|
|
|
|
However, the SchemaInfo can't reflect all the rules and restrictions
|
|
|
|
that apply to QMP. It's interface introspection (figuring out what's
|
|
|
|
there), not interface specification. The specification is in the QAPI
|
|
|
|
schema. To understand how QMP is to be used, you need to study the
|
|
|
|
QAPI schema.
|
|
|
|
|
|
|
|
Like any other command, query-qmp-schema is itself defined in the QAPI
|
|
|
|
schema, along with the SchemaInfo type. This text attempts to give an
|
|
|
|
overview how things work. For details you need to consult the QAPI
|
|
|
|
schema.
|
|
|
|
|
2020-03-17 14:54:37 +03:00
|
|
|
SchemaInfo objects have common members "name", "meta-type",
|
|
|
|
"features", and additional variant members depending on the value of
|
|
|
|
meta-type.
|
qapi: New QMP command query-qmp-schema for QMP introspection
qapi/introspect.json defines the introspection schema. It's designed
for QMP introspection, but should do for similar uses, such as QGA.
The introspection schema does not reflect all the rules and
restrictions that apply to QAPI schemata. A valid QAPI schema has an
introspection value conforming to the introspection schema, but the
converse is not true.
Introspection lowers away a number of schema details, and makes
implicit things explicit:
* The built-in types are declared with their JSON type.
All integer types are mapped to 'int', because how many bits we use
internally is an implementation detail. It could be pressed into
external interface service as very approximate range information,
but that's a bad idea. If we need range information, we better do
it properly.
* Implicit type definitions are made explicit, and given
auto-generated names:
- Array types, named by appending "List" to the name of their
element type, like in generated C.
- The enumeration types implicitly defined by simple union types,
named by appending "Kind" to the name of their simple union type,
like in generated C.
- Types that don't occur in generated C. Their names start with ':'
so they don't clash with the user's names.
* All type references are by name.
* The struct and union types are generalized into an object type.
* Base types are flattened.
* Commands take a single argument and return a single result.
Dictionary argument or list result is an implicit type definition.
The empty object type is used when a command takes no arguments or
produces no results.
The argument is always of object type, but the introspection schema
doesn't reflect that.
The 'gen': false directive is omitted as implementation detail.
The 'success-response' directive is omitted as well for now, even
though it's not an implementation detail, because it's not used by
QMP.
* Events carry a single data value.
Implicit type definition and empty object type use, just like for
commands.
The value is of object type, but the introspection schema doesn't
reflect that.
* Types not used by commands or events are omitted.
Indirect use counts as use.
* Optional members have a default, which can only be null right now
Instead of a mandatory "optional" flag, we have an optional default.
No default means mandatory, default null means optional without
default value. Non-null is available for optional with default
(possible future extension).
* Clients should *not* look up types by name, because type names are
not ABI. Look up the command or event you're interested in, then
follow the references.
TODO Should we hide the type names to eliminate the temptation?
New generator scripts/qapi-introspect.py computes an introspection
value for its input, and generates a C variable holding it.
It can generate awfully long lines. Marked TODO.
A new test-qmp-input-visitor test case feeds its result for both
tests/qapi-schema/qapi-schema-test.json and qapi-schema.json to a
QmpInputVisitor to verify it actually conforms to the schema.
New QMP command query-qmp-schema takes its return value from that
variable. Its reply is some 85KiBytes for me right now.
If this turns out to be too much, we have a couple of options:
* We can use shorter names in the JSON. Not the QMP style.
* Optionally return the sub-schema for commands and events given as
arguments.
Right now qmp_query_schema() sends the string literal computed by
qmp-introspect.py. To compute sub-schema at run time, we'd have to
duplicate parts of qapi-introspect.py in C. Unattractive.
* Let clients cache the output of query-qmp-schema.
It changes only on QEMU upgrades, i.e. rarely. Provide a command
query-qmp-schema-hash. Clients can have a cache indexed by hash,
and re-query the schema only when they don't have it cached. Even
simpler: put the hash in the QMP greeting.
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
2015-09-16 14:06:28 +03:00
|
|
|
|
|
|
|
Each SchemaInfo object describes a wire ABI entity of a certain
|
|
|
|
meta-type: a command, event or one of several kinds of type.
|
|
|
|
|
2015-09-16 14:06:29 +03:00
|
|
|
SchemaInfo for commands and events have the same name as in the QAPI
|
|
|
|
schema.
|
qapi: New QMP command query-qmp-schema for QMP introspection
qapi/introspect.json defines the introspection schema. It's designed
for QMP introspection, but should do for similar uses, such as QGA.
The introspection schema does not reflect all the rules and
restrictions that apply to QAPI schemata. A valid QAPI schema has an
introspection value conforming to the introspection schema, but the
converse is not true.
Introspection lowers away a number of schema details, and makes
implicit things explicit:
* The built-in types are declared with their JSON type.
All integer types are mapped to 'int', because how many bits we use
internally is an implementation detail. It could be pressed into
external interface service as very approximate range information,
but that's a bad idea. If we need range information, we better do
it properly.
* Implicit type definitions are made explicit, and given
auto-generated names:
- Array types, named by appending "List" to the name of their
element type, like in generated C.
- The enumeration types implicitly defined by simple union types,
named by appending "Kind" to the name of their simple union type,
like in generated C.
- Types that don't occur in generated C. Their names start with ':'
so they don't clash with the user's names.
* All type references are by name.
* The struct and union types are generalized into an object type.
* Base types are flattened.
* Commands take a single argument and return a single result.
Dictionary argument or list result is an implicit type definition.
The empty object type is used when a command takes no arguments or
produces no results.
The argument is always of object type, but the introspection schema
doesn't reflect that.
The 'gen': false directive is omitted as implementation detail.
The 'success-response' directive is omitted as well for now, even
though it's not an implementation detail, because it's not used by
QMP.
* Events carry a single data value.
Implicit type definition and empty object type use, just like for
commands.
The value is of object type, but the introspection schema doesn't
reflect that.
* Types not used by commands or events are omitted.
Indirect use counts as use.
* Optional members have a default, which can only be null right now
Instead of a mandatory "optional" flag, we have an optional default.
No default means mandatory, default null means optional without
default value. Non-null is available for optional with default
(possible future extension).
* Clients should *not* look up types by name, because type names are
not ABI. Look up the command or event you're interested in, then
follow the references.
TODO Should we hide the type names to eliminate the temptation?
New generator scripts/qapi-introspect.py computes an introspection
value for its input, and generates a C variable holding it.
It can generate awfully long lines. Marked TODO.
A new test-qmp-input-visitor test case feeds its result for both
tests/qapi-schema/qapi-schema-test.json and qapi-schema.json to a
QmpInputVisitor to verify it actually conforms to the schema.
New QMP command query-qmp-schema takes its return value from that
variable. Its reply is some 85KiBytes for me right now.
If this turns out to be too much, we have a couple of options:
* We can use shorter names in the JSON. Not the QMP style.
* Optionally return the sub-schema for commands and events given as
arguments.
Right now qmp_query_schema() sends the string literal computed by
qmp-introspect.py. To compute sub-schema at run time, we'd have to
duplicate parts of qapi-introspect.py in C. Unattractive.
* Let clients cache the output of query-qmp-schema.
It changes only on QEMU upgrades, i.e. rarely. Provide a command
query-qmp-schema-hash. Clients can have a cache indexed by hash,
and re-query the schema only when they don't have it cached. Even
simpler: put the hash in the QMP greeting.
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
2015-09-16 14:06:28 +03:00
|
|
|
|
|
|
|
Command and event names are part of the wire ABI, but type names are
|
2015-09-16 14:06:29 +03:00
|
|
|
not. Therefore, the SchemaInfo for types have auto-generated
|
|
|
|
meaningless names. For readability, the examples in this section use
|
|
|
|
meaningful type names instead.
|
|
|
|
|
2020-03-17 14:54:37 +03:00
|
|
|
Optional member "features" exposes the entity's feature strings as a
|
|
|
|
JSON array of strings.
|
|
|
|
|
2015-09-16 14:06:29 +03:00
|
|
|
To examine a type, start with a command or event using it, then follow
|
|
|
|
references by name.
|
qapi: New QMP command query-qmp-schema for QMP introspection
qapi/introspect.json defines the introspection schema. It's designed
for QMP introspection, but should do for similar uses, such as QGA.
The introspection schema does not reflect all the rules and
restrictions that apply to QAPI schemata. A valid QAPI schema has an
introspection value conforming to the introspection schema, but the
converse is not true.
Introspection lowers away a number of schema details, and makes
implicit things explicit:
* The built-in types are declared with their JSON type.
All integer types are mapped to 'int', because how many bits we use
internally is an implementation detail. It could be pressed into
external interface service as very approximate range information,
but that's a bad idea. If we need range information, we better do
it properly.
* Implicit type definitions are made explicit, and given
auto-generated names:
- Array types, named by appending "List" to the name of their
element type, like in generated C.
- The enumeration types implicitly defined by simple union types,
named by appending "Kind" to the name of their simple union type,
like in generated C.
- Types that don't occur in generated C. Their names start with ':'
so they don't clash with the user's names.
* All type references are by name.
* The struct and union types are generalized into an object type.
* Base types are flattened.
* Commands take a single argument and return a single result.
Dictionary argument or list result is an implicit type definition.
The empty object type is used when a command takes no arguments or
produces no results.
The argument is always of object type, but the introspection schema
doesn't reflect that.
The 'gen': false directive is omitted as implementation detail.
The 'success-response' directive is omitted as well for now, even
though it's not an implementation detail, because it's not used by
QMP.
* Events carry a single data value.
Implicit type definition and empty object type use, just like for
commands.
The value is of object type, but the introspection schema doesn't
reflect that.
* Types not used by commands or events are omitted.
Indirect use counts as use.
* Optional members have a default, which can only be null right now
Instead of a mandatory "optional" flag, we have an optional default.
No default means mandatory, default null means optional without
default value. Non-null is available for optional with default
(possible future extension).
* Clients should *not* look up types by name, because type names are
not ABI. Look up the command or event you're interested in, then
follow the references.
TODO Should we hide the type names to eliminate the temptation?
New generator scripts/qapi-introspect.py computes an introspection
value for its input, and generates a C variable holding it.
It can generate awfully long lines. Marked TODO.
A new test-qmp-input-visitor test case feeds its result for both
tests/qapi-schema/qapi-schema-test.json and qapi-schema.json to a
QmpInputVisitor to verify it actually conforms to the schema.
New QMP command query-qmp-schema takes its return value from that
variable. Its reply is some 85KiBytes for me right now.
If this turns out to be too much, we have a couple of options:
* We can use shorter names in the JSON. Not the QMP style.
* Optionally return the sub-schema for commands and events given as
arguments.
Right now qmp_query_schema() sends the string literal computed by
qmp-introspect.py. To compute sub-schema at run time, we'd have to
duplicate parts of qapi-introspect.py in C. Unattractive.
* Let clients cache the output of query-qmp-schema.
It changes only on QEMU upgrades, i.e. rarely. Provide a command
query-qmp-schema-hash. Clients can have a cache indexed by hash,
and re-query the schema only when they don't have it cached. Even
simpler: put the hash in the QMP greeting.
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
2015-09-16 14:06:28 +03:00
|
|
|
|
|
|
|
QAPI schema definitions not reachable that way are omitted.
|
|
|
|
|
|
|
|
The SchemaInfo for a command has meta-type "command", and variant
|
2020-03-17 14:54:37 +03:00
|
|
|
members "arg-type", "ret-type" and "allow-oob". On the wire, the
|
|
|
|
"arguments" member of a client's "execute" command must conform to the
|
|
|
|
object type named by "arg-type". The "return" member that the server
|
|
|
|
passes in a success response conforms to the type named by "ret-type".
|
|
|
|
When "allow-oob" is true, it means the command supports out-of-band
|
|
|
|
execution. It defaults to false.
|
qapi: New QMP command query-qmp-schema for QMP introspection
qapi/introspect.json defines the introspection schema. It's designed
for QMP introspection, but should do for similar uses, such as QGA.
The introspection schema does not reflect all the rules and
restrictions that apply to QAPI schemata. A valid QAPI schema has an
introspection value conforming to the introspection schema, but the
converse is not true.
Introspection lowers away a number of schema details, and makes
implicit things explicit:
* The built-in types are declared with their JSON type.
All integer types are mapped to 'int', because how many bits we use
internally is an implementation detail. It could be pressed into
external interface service as very approximate range information,
but that's a bad idea. If we need range information, we better do
it properly.
* Implicit type definitions are made explicit, and given
auto-generated names:
- Array types, named by appending "List" to the name of their
element type, like in generated C.
- The enumeration types implicitly defined by simple union types,
named by appending "Kind" to the name of their simple union type,
like in generated C.
- Types that don't occur in generated C. Their names start with ':'
so they don't clash with the user's names.
* All type references are by name.
* The struct and union types are generalized into an object type.
* Base types are flattened.
* Commands take a single argument and return a single result.
Dictionary argument or list result is an implicit type definition.
The empty object type is used when a command takes no arguments or
produces no results.
The argument is always of object type, but the introspection schema
doesn't reflect that.
The 'gen': false directive is omitted as implementation detail.
The 'success-response' directive is omitted as well for now, even
though it's not an implementation detail, because it's not used by
QMP.
* Events carry a single data value.
Implicit type definition and empty object type use, just like for
commands.
The value is of object type, but the introspection schema doesn't
reflect that.
* Types not used by commands or events are omitted.
Indirect use counts as use.
* Optional members have a default, which can only be null right now
Instead of a mandatory "optional" flag, we have an optional default.
No default means mandatory, default null means optional without
default value. Non-null is available for optional with default
(possible future extension).
* Clients should *not* look up types by name, because type names are
not ABI. Look up the command or event you're interested in, then
follow the references.
TODO Should we hide the type names to eliminate the temptation?
New generator scripts/qapi-introspect.py computes an introspection
value for its input, and generates a C variable holding it.
It can generate awfully long lines. Marked TODO.
A new test-qmp-input-visitor test case feeds its result for both
tests/qapi-schema/qapi-schema-test.json and qapi-schema.json to a
QmpInputVisitor to verify it actually conforms to the schema.
New QMP command query-qmp-schema takes its return value from that
variable. Its reply is some 85KiBytes for me right now.
If this turns out to be too much, we have a couple of options:
* We can use shorter names in the JSON. Not the QMP style.
* Optionally return the sub-schema for commands and events given as
arguments.
Right now qmp_query_schema() sends the string literal computed by
qmp-introspect.py. To compute sub-schema at run time, we'd have to
duplicate parts of qapi-introspect.py in C. Unattractive.
* Let clients cache the output of query-qmp-schema.
It changes only on QEMU upgrades, i.e. rarely. Provide a command
query-qmp-schema-hash. Clients can have a cache indexed by hash,
and re-query the schema only when they don't have it cached. Even
simpler: put the hash in the QMP greeting.
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
2015-09-16 14:06:28 +03:00
|
|
|
|
|
|
|
If the command takes no arguments, "arg-type" names an object type
|
|
|
|
without members. Likewise, if the command returns nothing, "ret-type"
|
|
|
|
names an object type without members.
|
|
|
|
|
2021-07-21 02:56:17 +03:00
|
|
|
Example: the SchemaInfo for command query-qmp-schema ::
|
qapi: New QMP command query-qmp-schema for QMP introspection
qapi/introspect.json defines the introspection schema. It's designed
for QMP introspection, but should do for similar uses, such as QGA.
The introspection schema does not reflect all the rules and
restrictions that apply to QAPI schemata. A valid QAPI schema has an
introspection value conforming to the introspection schema, but the
converse is not true.
Introspection lowers away a number of schema details, and makes
implicit things explicit:
* The built-in types are declared with their JSON type.
All integer types are mapped to 'int', because how many bits we use
internally is an implementation detail. It could be pressed into
external interface service as very approximate range information,
but that's a bad idea. If we need range information, we better do
it properly.
* Implicit type definitions are made explicit, and given
auto-generated names:
- Array types, named by appending "List" to the name of their
element type, like in generated C.
- The enumeration types implicitly defined by simple union types,
named by appending "Kind" to the name of their simple union type,
like in generated C.
- Types that don't occur in generated C. Their names start with ':'
so they don't clash with the user's names.
* All type references are by name.
* The struct and union types are generalized into an object type.
* Base types are flattened.
* Commands take a single argument and return a single result.
Dictionary argument or list result is an implicit type definition.
The empty object type is used when a command takes no arguments or
produces no results.
The argument is always of object type, but the introspection schema
doesn't reflect that.
The 'gen': false directive is omitted as implementation detail.
The 'success-response' directive is omitted as well for now, even
though it's not an implementation detail, because it's not used by
QMP.
* Events carry a single data value.
Implicit type definition and empty object type use, just like for
commands.
The value is of object type, but the introspection schema doesn't
reflect that.
* Types not used by commands or events are omitted.
Indirect use counts as use.
* Optional members have a default, which can only be null right now
Instead of a mandatory "optional" flag, we have an optional default.
No default means mandatory, default null means optional without
default value. Non-null is available for optional with default
(possible future extension).
* Clients should *not* look up types by name, because type names are
not ABI. Look up the command or event you're interested in, then
follow the references.
TODO Should we hide the type names to eliminate the temptation?
New generator scripts/qapi-introspect.py computes an introspection
value for its input, and generates a C variable holding it.
It can generate awfully long lines. Marked TODO.
A new test-qmp-input-visitor test case feeds its result for both
tests/qapi-schema/qapi-schema-test.json and qapi-schema.json to a
QmpInputVisitor to verify it actually conforms to the schema.
New QMP command query-qmp-schema takes its return value from that
variable. Its reply is some 85KiBytes for me right now.
If this turns out to be too much, we have a couple of options:
* We can use shorter names in the JSON. Not the QMP style.
* Optionally return the sub-schema for commands and events given as
arguments.
Right now qmp_query_schema() sends the string literal computed by
qmp-introspect.py. To compute sub-schema at run time, we'd have to
duplicate parts of qapi-introspect.py in C. Unattractive.
* Let clients cache the output of query-qmp-schema.
It changes only on QEMU upgrades, i.e. rarely. Provide a command
query-qmp-schema-hash. Clients can have a cache indexed by hash,
and re-query the schema only when they don't have it cached. Even
simpler: put the hash in the QMP greeting.
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
2015-09-16 14:06:28 +03:00
|
|
|
|
2021-07-21 02:56:17 +03:00
|
|
|
{ "name": "query-qmp-schema", "meta-type": "command",
|
|
|
|
"arg-type": "q_empty", "ret-type": "SchemaInfoList" }
|
qapi: New QMP command query-qmp-schema for QMP introspection
qapi/introspect.json defines the introspection schema. It's designed
for QMP introspection, but should do for similar uses, such as QGA.
The introspection schema does not reflect all the rules and
restrictions that apply to QAPI schemata. A valid QAPI schema has an
introspection value conforming to the introspection schema, but the
converse is not true.
Introspection lowers away a number of schema details, and makes
implicit things explicit:
* The built-in types are declared with their JSON type.
All integer types are mapped to 'int', because how many bits we use
internally is an implementation detail. It could be pressed into
external interface service as very approximate range information,
but that's a bad idea. If we need range information, we better do
it properly.
* Implicit type definitions are made explicit, and given
auto-generated names:
- Array types, named by appending "List" to the name of their
element type, like in generated C.
- The enumeration types implicitly defined by simple union types,
named by appending "Kind" to the name of their simple union type,
like in generated C.
- Types that don't occur in generated C. Their names start with ':'
so they don't clash with the user's names.
* All type references are by name.
* The struct and union types are generalized into an object type.
* Base types are flattened.
* Commands take a single argument and return a single result.
Dictionary argument or list result is an implicit type definition.
The empty object type is used when a command takes no arguments or
produces no results.
The argument is always of object type, but the introspection schema
doesn't reflect that.
The 'gen': false directive is omitted as implementation detail.
The 'success-response' directive is omitted as well for now, even
though it's not an implementation detail, because it's not used by
QMP.
* Events carry a single data value.
Implicit type definition and empty object type use, just like for
commands.
The value is of object type, but the introspection schema doesn't
reflect that.
* Types not used by commands or events are omitted.
Indirect use counts as use.
* Optional members have a default, which can only be null right now
Instead of a mandatory "optional" flag, we have an optional default.
No default means mandatory, default null means optional without
default value. Non-null is available for optional with default
(possible future extension).
* Clients should *not* look up types by name, because type names are
not ABI. Look up the command or event you're interested in, then
follow the references.
TODO Should we hide the type names to eliminate the temptation?
New generator scripts/qapi-introspect.py computes an introspection
value for its input, and generates a C variable holding it.
It can generate awfully long lines. Marked TODO.
A new test-qmp-input-visitor test case feeds its result for both
tests/qapi-schema/qapi-schema-test.json and qapi-schema.json to a
QmpInputVisitor to verify it actually conforms to the schema.
New QMP command query-qmp-schema takes its return value from that
variable. Its reply is some 85KiBytes for me right now.
If this turns out to be too much, we have a couple of options:
* We can use shorter names in the JSON. Not the QMP style.
* Optionally return the sub-schema for commands and events given as
arguments.
Right now qmp_query_schema() sends the string literal computed by
qmp-introspect.py. To compute sub-schema at run time, we'd have to
duplicate parts of qapi-introspect.py in C. Unattractive.
* Let clients cache the output of query-qmp-schema.
It changes only on QEMU upgrades, i.e. rarely. Provide a command
query-qmp-schema-hash. Clients can have a cache indexed by hash,
and re-query the schema only when they don't have it cached. Even
simpler: put the hash in the QMP greeting.
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
2015-09-16 14:06:28 +03:00
|
|
|
|
2021-07-21 02:56:17 +03:00
|
|
|
Type "q_empty" is an automatic object type without members, and type
|
|
|
|
"SchemaInfoList" is the array of SchemaInfo type.
|
qapi: New QMP command query-qmp-schema for QMP introspection
qapi/introspect.json defines the introspection schema. It's designed
for QMP introspection, but should do for similar uses, such as QGA.
The introspection schema does not reflect all the rules and
restrictions that apply to QAPI schemata. A valid QAPI schema has an
introspection value conforming to the introspection schema, but the
converse is not true.
Introspection lowers away a number of schema details, and makes
implicit things explicit:
* The built-in types are declared with their JSON type.
All integer types are mapped to 'int', because how many bits we use
internally is an implementation detail. It could be pressed into
external interface service as very approximate range information,
but that's a bad idea. If we need range information, we better do
it properly.
* Implicit type definitions are made explicit, and given
auto-generated names:
- Array types, named by appending "List" to the name of their
element type, like in generated C.
- The enumeration types implicitly defined by simple union types,
named by appending "Kind" to the name of their simple union type,
like in generated C.
- Types that don't occur in generated C. Their names start with ':'
so they don't clash with the user's names.
* All type references are by name.
* The struct and union types are generalized into an object type.
* Base types are flattened.
* Commands take a single argument and return a single result.
Dictionary argument or list result is an implicit type definition.
The empty object type is used when a command takes no arguments or
produces no results.
The argument is always of object type, but the introspection schema
doesn't reflect that.
The 'gen': false directive is omitted as implementation detail.
The 'success-response' directive is omitted as well for now, even
though it's not an implementation detail, because it's not used by
QMP.
* Events carry a single data value.
Implicit type definition and empty object type use, just like for
commands.
The value is of object type, but the introspection schema doesn't
reflect that.
* Types not used by commands or events are omitted.
Indirect use counts as use.
* Optional members have a default, which can only be null right now
Instead of a mandatory "optional" flag, we have an optional default.
No default means mandatory, default null means optional without
default value. Non-null is available for optional with default
(possible future extension).
* Clients should *not* look up types by name, because type names are
not ABI. Look up the command or event you're interested in, then
follow the references.
TODO Should we hide the type names to eliminate the temptation?
New generator scripts/qapi-introspect.py computes an introspection
value for its input, and generates a C variable holding it.
It can generate awfully long lines. Marked TODO.
A new test-qmp-input-visitor test case feeds its result for both
tests/qapi-schema/qapi-schema-test.json and qapi-schema.json to a
QmpInputVisitor to verify it actually conforms to the schema.
New QMP command query-qmp-schema takes its return value from that
variable. Its reply is some 85KiBytes for me right now.
If this turns out to be too much, we have a couple of options:
* We can use shorter names in the JSON. Not the QMP style.
* Optionally return the sub-schema for commands and events given as
arguments.
Right now qmp_query_schema() sends the string literal computed by
qmp-introspect.py. To compute sub-schema at run time, we'd have to
duplicate parts of qapi-introspect.py in C. Unattractive.
* Let clients cache the output of query-qmp-schema.
It changes only on QEMU upgrades, i.e. rarely. Provide a command
query-qmp-schema-hash. Clients can have a cache indexed by hash,
and re-query the schema only when they don't have it cached. Even
simpler: put the hash in the QMP greeting.
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
2015-09-16 14:06:28 +03:00
|
|
|
|
|
|
|
The SchemaInfo for an event has meta-type "event", and variant member
|
|
|
|
"arg-type". On the wire, a "data" member that the server passes in an
|
|
|
|
event conforms to the object type named by "arg-type".
|
|
|
|
|
|
|
|
If the event carries no additional information, "arg-type" names an
|
|
|
|
object type without members. The event may not have a data member on
|
|
|
|
the wire then.
|
|
|
|
|
2019-09-13 23:13:48 +03:00
|
|
|
Each command or event defined with 'data' as MEMBERS object in the
|
2015-09-16 14:06:29 +03:00
|
|
|
QAPI schema implicitly defines an object type.
|
qapi: New QMP command query-qmp-schema for QMP introspection
qapi/introspect.json defines the introspection schema. It's designed
for QMP introspection, but should do for similar uses, such as QGA.
The introspection schema does not reflect all the rules and
restrictions that apply to QAPI schemata. A valid QAPI schema has an
introspection value conforming to the introspection schema, but the
converse is not true.
Introspection lowers away a number of schema details, and makes
implicit things explicit:
* The built-in types are declared with their JSON type.
All integer types are mapped to 'int', because how many bits we use
internally is an implementation detail. It could be pressed into
external interface service as very approximate range information,
but that's a bad idea. If we need range information, we better do
it properly.
* Implicit type definitions are made explicit, and given
auto-generated names:
- Array types, named by appending "List" to the name of their
element type, like in generated C.
- The enumeration types implicitly defined by simple union types,
named by appending "Kind" to the name of their simple union type,
like in generated C.
- Types that don't occur in generated C. Their names start with ':'
so they don't clash with the user's names.
* All type references are by name.
* The struct and union types are generalized into an object type.
* Base types are flattened.
* Commands take a single argument and return a single result.
Dictionary argument or list result is an implicit type definition.
The empty object type is used when a command takes no arguments or
produces no results.
The argument is always of object type, but the introspection schema
doesn't reflect that.
The 'gen': false directive is omitted as implementation detail.
The 'success-response' directive is omitted as well for now, even
though it's not an implementation detail, because it's not used by
QMP.
* Events carry a single data value.
Implicit type definition and empty object type use, just like for
commands.
The value is of object type, but the introspection schema doesn't
reflect that.
* Types not used by commands or events are omitted.
Indirect use counts as use.
* Optional members have a default, which can only be null right now
Instead of a mandatory "optional" flag, we have an optional default.
No default means mandatory, default null means optional without
default value. Non-null is available for optional with default
(possible future extension).
* Clients should *not* look up types by name, because type names are
not ABI. Look up the command or event you're interested in, then
follow the references.
TODO Should we hide the type names to eliminate the temptation?
New generator scripts/qapi-introspect.py computes an introspection
value for its input, and generates a C variable holding it.
It can generate awfully long lines. Marked TODO.
A new test-qmp-input-visitor test case feeds its result for both
tests/qapi-schema/qapi-schema-test.json and qapi-schema.json to a
QmpInputVisitor to verify it actually conforms to the schema.
New QMP command query-qmp-schema takes its return value from that
variable. Its reply is some 85KiBytes for me right now.
If this turns out to be too much, we have a couple of options:
* We can use shorter names in the JSON. Not the QMP style.
* Optionally return the sub-schema for commands and events given as
arguments.
Right now qmp_query_schema() sends the string literal computed by
qmp-introspect.py. To compute sub-schema at run time, we'd have to
duplicate parts of qapi-introspect.py in C. Unattractive.
* Let clients cache the output of query-qmp-schema.
It changes only on QEMU upgrades, i.e. rarely. Provide a command
query-qmp-schema-hash. Clients can have a cache indexed by hash,
and re-query the schema only when they don't have it cached. Even
simpler: put the hash in the QMP greeting.
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
2015-09-16 14:06:28 +03:00
|
|
|
|
2021-07-21 02:56:19 +03:00
|
|
|
Example: the SchemaInfo for EVENT_C from section Events_ ::
|
qapi: New QMP command query-qmp-schema for QMP introspection
qapi/introspect.json defines the introspection schema. It's designed
for QMP introspection, but should do for similar uses, such as QGA.
The introspection schema does not reflect all the rules and
restrictions that apply to QAPI schemata. A valid QAPI schema has an
introspection value conforming to the introspection schema, but the
converse is not true.
Introspection lowers away a number of schema details, and makes
implicit things explicit:
* The built-in types are declared with their JSON type.
All integer types are mapped to 'int', because how many bits we use
internally is an implementation detail. It could be pressed into
external interface service as very approximate range information,
but that's a bad idea. If we need range information, we better do
it properly.
* Implicit type definitions are made explicit, and given
auto-generated names:
- Array types, named by appending "List" to the name of their
element type, like in generated C.
- The enumeration types implicitly defined by simple union types,
named by appending "Kind" to the name of their simple union type,
like in generated C.
- Types that don't occur in generated C. Their names start with ':'
so they don't clash with the user's names.
* All type references are by name.
* The struct and union types are generalized into an object type.
* Base types are flattened.
* Commands take a single argument and return a single result.
Dictionary argument or list result is an implicit type definition.
The empty object type is used when a command takes no arguments or
produces no results.
The argument is always of object type, but the introspection schema
doesn't reflect that.
The 'gen': false directive is omitted as implementation detail.
The 'success-response' directive is omitted as well for now, even
though it's not an implementation detail, because it's not used by
QMP.
* Events carry a single data value.
Implicit type definition and empty object type use, just like for
commands.
The value is of object type, but the introspection schema doesn't
reflect that.
* Types not used by commands or events are omitted.
Indirect use counts as use.
* Optional members have a default, which can only be null right now
Instead of a mandatory "optional" flag, we have an optional default.
No default means mandatory, default null means optional without
default value. Non-null is available for optional with default
(possible future extension).
* Clients should *not* look up types by name, because type names are
not ABI. Look up the command or event you're interested in, then
follow the references.
TODO Should we hide the type names to eliminate the temptation?
New generator scripts/qapi-introspect.py computes an introspection
value for its input, and generates a C variable holding it.
It can generate awfully long lines. Marked TODO.
A new test-qmp-input-visitor test case feeds its result for both
tests/qapi-schema/qapi-schema-test.json and qapi-schema.json to a
QmpInputVisitor to verify it actually conforms to the schema.
New QMP command query-qmp-schema takes its return value from that
variable. Its reply is some 85KiBytes for me right now.
If this turns out to be too much, we have a couple of options:
* We can use shorter names in the JSON. Not the QMP style.
* Optionally return the sub-schema for commands and events given as
arguments.
Right now qmp_query_schema() sends the string literal computed by
qmp-introspect.py. To compute sub-schema at run time, we'd have to
duplicate parts of qapi-introspect.py in C. Unattractive.
* Let clients cache the output of query-qmp-schema.
It changes only on QEMU upgrades, i.e. rarely. Provide a command
query-qmp-schema-hash. Clients can have a cache indexed by hash,
and re-query the schema only when they don't have it cached. Even
simpler: put the hash in the QMP greeting.
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
2015-09-16 14:06:28 +03:00
|
|
|
|
|
|
|
{ "name": "EVENT_C", "meta-type": "event",
|
2016-03-18 01:48:29 +03:00
|
|
|
"arg-type": "q_obj-EVENT_C-arg" }
|
qapi: New QMP command query-qmp-schema for QMP introspection
qapi/introspect.json defines the introspection schema. It's designed
for QMP introspection, but should do for similar uses, such as QGA.
The introspection schema does not reflect all the rules and
restrictions that apply to QAPI schemata. A valid QAPI schema has an
introspection value conforming to the introspection schema, but the
converse is not true.
Introspection lowers away a number of schema details, and makes
implicit things explicit:
* The built-in types are declared with their JSON type.
All integer types are mapped to 'int', because how many bits we use
internally is an implementation detail. It could be pressed into
external interface service as very approximate range information,
but that's a bad idea. If we need range information, we better do
it properly.
* Implicit type definitions are made explicit, and given
auto-generated names:
- Array types, named by appending "List" to the name of their
element type, like in generated C.
- The enumeration types implicitly defined by simple union types,
named by appending "Kind" to the name of their simple union type,
like in generated C.
- Types that don't occur in generated C. Their names start with ':'
so they don't clash with the user's names.
* All type references are by name.
* The struct and union types are generalized into an object type.
* Base types are flattened.
* Commands take a single argument and return a single result.
Dictionary argument or list result is an implicit type definition.
The empty object type is used when a command takes no arguments or
produces no results.
The argument is always of object type, but the introspection schema
doesn't reflect that.
The 'gen': false directive is omitted as implementation detail.
The 'success-response' directive is omitted as well for now, even
though it's not an implementation detail, because it's not used by
QMP.
* Events carry a single data value.
Implicit type definition and empty object type use, just like for
commands.
The value is of object type, but the introspection schema doesn't
reflect that.
* Types not used by commands or events are omitted.
Indirect use counts as use.
* Optional members have a default, which can only be null right now
Instead of a mandatory "optional" flag, we have an optional default.
No default means mandatory, default null means optional without
default value. Non-null is available for optional with default
(possible future extension).
* Clients should *not* look up types by name, because type names are
not ABI. Look up the command or event you're interested in, then
follow the references.
TODO Should we hide the type names to eliminate the temptation?
New generator scripts/qapi-introspect.py computes an introspection
value for its input, and generates a C variable holding it.
It can generate awfully long lines. Marked TODO.
A new test-qmp-input-visitor test case feeds its result for both
tests/qapi-schema/qapi-schema-test.json and qapi-schema.json to a
QmpInputVisitor to verify it actually conforms to the schema.
New QMP command query-qmp-schema takes its return value from that
variable. Its reply is some 85KiBytes for me right now.
If this turns out to be too much, we have a couple of options:
* We can use shorter names in the JSON. Not the QMP style.
* Optionally return the sub-schema for commands and events given as
arguments.
Right now qmp_query_schema() sends the string literal computed by
qmp-introspect.py. To compute sub-schema at run time, we'd have to
duplicate parts of qapi-introspect.py in C. Unattractive.
* Let clients cache the output of query-qmp-schema.
It changes only on QEMU upgrades, i.e. rarely. Provide a command
query-qmp-schema-hash. Clients can have a cache indexed by hash,
and re-query the schema only when they don't have it cached. Even
simpler: put the hash in the QMP greeting.
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
2015-09-16 14:06:28 +03:00
|
|
|
|
2016-03-18 01:48:29 +03:00
|
|
|
Type "q_obj-EVENT_C-arg" is an implicitly defined object type with
|
qapi: New QMP command query-qmp-schema for QMP introspection
qapi/introspect.json defines the introspection schema. It's designed
for QMP introspection, but should do for similar uses, such as QGA.
The introspection schema does not reflect all the rules and
restrictions that apply to QAPI schemata. A valid QAPI schema has an
introspection value conforming to the introspection schema, but the
converse is not true.
Introspection lowers away a number of schema details, and makes
implicit things explicit:
* The built-in types are declared with their JSON type.
All integer types are mapped to 'int', because how many bits we use
internally is an implementation detail. It could be pressed into
external interface service as very approximate range information,
but that's a bad idea. If we need range information, we better do
it properly.
* Implicit type definitions are made explicit, and given
auto-generated names:
- Array types, named by appending "List" to the name of their
element type, like in generated C.
- The enumeration types implicitly defined by simple union types,
named by appending "Kind" to the name of their simple union type,
like in generated C.
- Types that don't occur in generated C. Their names start with ':'
so they don't clash with the user's names.
* All type references are by name.
* The struct and union types are generalized into an object type.
* Base types are flattened.
* Commands take a single argument and return a single result.
Dictionary argument or list result is an implicit type definition.
The empty object type is used when a command takes no arguments or
produces no results.
The argument is always of object type, but the introspection schema
doesn't reflect that.
The 'gen': false directive is omitted as implementation detail.
The 'success-response' directive is omitted as well for now, even
though it's not an implementation detail, because it's not used by
QMP.
* Events carry a single data value.
Implicit type definition and empty object type use, just like for
commands.
The value is of object type, but the introspection schema doesn't
reflect that.
* Types not used by commands or events are omitted.
Indirect use counts as use.
* Optional members have a default, which can only be null right now
Instead of a mandatory "optional" flag, we have an optional default.
No default means mandatory, default null means optional without
default value. Non-null is available for optional with default
(possible future extension).
* Clients should *not* look up types by name, because type names are
not ABI. Look up the command or event you're interested in, then
follow the references.
TODO Should we hide the type names to eliminate the temptation?
New generator scripts/qapi-introspect.py computes an introspection
value for its input, and generates a C variable holding it.
It can generate awfully long lines. Marked TODO.
A new test-qmp-input-visitor test case feeds its result for both
tests/qapi-schema/qapi-schema-test.json and qapi-schema.json to a
QmpInputVisitor to verify it actually conforms to the schema.
New QMP command query-qmp-schema takes its return value from that
variable. Its reply is some 85KiBytes for me right now.
If this turns out to be too much, we have a couple of options:
* We can use shorter names in the JSON. Not the QMP style.
* Optionally return the sub-schema for commands and events given as
arguments.
Right now qmp_query_schema() sends the string literal computed by
qmp-introspect.py. To compute sub-schema at run time, we'd have to
duplicate parts of qapi-introspect.py in C. Unattractive.
* Let clients cache the output of query-qmp-schema.
It changes only on QEMU upgrades, i.e. rarely. Provide a command
query-qmp-schema-hash. Clients can have a cache indexed by hash,
and re-query the schema only when they don't have it cached. Even
simpler: put the hash in the QMP greeting.
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
2015-09-16 14:06:28 +03:00
|
|
|
the two members from the event's definition.
|
|
|
|
|
2023-02-13 16:20:09 +03:00
|
|
|
The SchemaInfo for struct and union types has meta-type "object" and
|
|
|
|
variant member "members".
|
qapi: New QMP command query-qmp-schema for QMP introspection
qapi/introspect.json defines the introspection schema. It's designed
for QMP introspection, but should do for similar uses, such as QGA.
The introspection schema does not reflect all the rules and
restrictions that apply to QAPI schemata. A valid QAPI schema has an
introspection value conforming to the introspection schema, but the
converse is not true.
Introspection lowers away a number of schema details, and makes
implicit things explicit:
* The built-in types are declared with their JSON type.
All integer types are mapped to 'int', because how many bits we use
internally is an implementation detail. It could be pressed into
external interface service as very approximate range information,
but that's a bad idea. If we need range information, we better do
it properly.
* Implicit type definitions are made explicit, and given
auto-generated names:
- Array types, named by appending "List" to the name of their
element type, like in generated C.
- The enumeration types implicitly defined by simple union types,
named by appending "Kind" to the name of their simple union type,
like in generated C.
- Types that don't occur in generated C. Their names start with ':'
so they don't clash with the user's names.
* All type references are by name.
* The struct and union types are generalized into an object type.
* Base types are flattened.
* Commands take a single argument and return a single result.
Dictionary argument or list result is an implicit type definition.
The empty object type is used when a command takes no arguments or
produces no results.
The argument is always of object type, but the introspection schema
doesn't reflect that.
The 'gen': false directive is omitted as implementation detail.
The 'success-response' directive is omitted as well for now, even
though it's not an implementation detail, because it's not used by
QMP.
* Events carry a single data value.
Implicit type definition and empty object type use, just like for
commands.
The value is of object type, but the introspection schema doesn't
reflect that.
* Types not used by commands or events are omitted.
Indirect use counts as use.
* Optional members have a default, which can only be null right now
Instead of a mandatory "optional" flag, we have an optional default.
No default means mandatory, default null means optional without
default value. Non-null is available for optional with default
(possible future extension).
* Clients should *not* look up types by name, because type names are
not ABI. Look up the command or event you're interested in, then
follow the references.
TODO Should we hide the type names to eliminate the temptation?
New generator scripts/qapi-introspect.py computes an introspection
value for its input, and generates a C variable holding it.
It can generate awfully long lines. Marked TODO.
A new test-qmp-input-visitor test case feeds its result for both
tests/qapi-schema/qapi-schema-test.json and qapi-schema.json to a
QmpInputVisitor to verify it actually conforms to the schema.
New QMP command query-qmp-schema takes its return value from that
variable. Its reply is some 85KiBytes for me right now.
If this turns out to be too much, we have a couple of options:
* We can use shorter names in the JSON. Not the QMP style.
* Optionally return the sub-schema for commands and events given as
arguments.
Right now qmp_query_schema() sends the string literal computed by
qmp-introspect.py. To compute sub-schema at run time, we'd have to
duplicate parts of qapi-introspect.py in C. Unattractive.
* Let clients cache the output of query-qmp-schema.
It changes only on QEMU upgrades, i.e. rarely. Provide a command
query-qmp-schema-hash. Clients can have a cache indexed by hash,
and re-query the schema only when they don't have it cached. Even
simpler: put the hash in the QMP greeting.
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
2015-09-16 14:06:28 +03:00
|
|
|
|
|
|
|
The SchemaInfo for a union type additionally has variant members "tag"
|
|
|
|
and "variants".
|
|
|
|
|
|
|
|
"members" is a JSON array describing the object's common members, if
|
|
|
|
any. Each element is a JSON object with members "name" (the member's
|
2021-10-25 07:24:02 +03:00
|
|
|
name), "type" (the name of its type), "features" (a JSON array of
|
|
|
|
feature strings), and "default". The latter two are optional. The
|
qapi: New QMP command query-qmp-schema for QMP introspection
qapi/introspect.json defines the introspection schema. It's designed
for QMP introspection, but should do for similar uses, such as QGA.
The introspection schema does not reflect all the rules and
restrictions that apply to QAPI schemata. A valid QAPI schema has an
introspection value conforming to the introspection schema, but the
converse is not true.
Introspection lowers away a number of schema details, and makes
implicit things explicit:
* The built-in types are declared with their JSON type.
All integer types are mapped to 'int', because how many bits we use
internally is an implementation detail. It could be pressed into
external interface service as very approximate range information,
but that's a bad idea. If we need range information, we better do
it properly.
* Implicit type definitions are made explicit, and given
auto-generated names:
- Array types, named by appending "List" to the name of their
element type, like in generated C.
- The enumeration types implicitly defined by simple union types,
named by appending "Kind" to the name of their simple union type,
like in generated C.
- Types that don't occur in generated C. Their names start with ':'
so they don't clash with the user's names.
* All type references are by name.
* The struct and union types are generalized into an object type.
* Base types are flattened.
* Commands take a single argument and return a single result.
Dictionary argument or list result is an implicit type definition.
The empty object type is used when a command takes no arguments or
produces no results.
The argument is always of object type, but the introspection schema
doesn't reflect that.
The 'gen': false directive is omitted as implementation detail.
The 'success-response' directive is omitted as well for now, even
though it's not an implementation detail, because it's not used by
QMP.
* Events carry a single data value.
Implicit type definition and empty object type use, just like for
commands.
The value is of object type, but the introspection schema doesn't
reflect that.
* Types not used by commands or events are omitted.
Indirect use counts as use.
* Optional members have a default, which can only be null right now
Instead of a mandatory "optional" flag, we have an optional default.
No default means mandatory, default null means optional without
default value. Non-null is available for optional with default
(possible future extension).
* Clients should *not* look up types by name, because type names are
not ABI. Look up the command or event you're interested in, then
follow the references.
TODO Should we hide the type names to eliminate the temptation?
New generator scripts/qapi-introspect.py computes an introspection
value for its input, and generates a C variable holding it.
It can generate awfully long lines. Marked TODO.
A new test-qmp-input-visitor test case feeds its result for both
tests/qapi-schema/qapi-schema-test.json and qapi-schema.json to a
QmpInputVisitor to verify it actually conforms to the schema.
New QMP command query-qmp-schema takes its return value from that
variable. Its reply is some 85KiBytes for me right now.
If this turns out to be too much, we have a couple of options:
* We can use shorter names in the JSON. Not the QMP style.
* Optionally return the sub-schema for commands and events given as
arguments.
Right now qmp_query_schema() sends the string literal computed by
qmp-introspect.py. To compute sub-schema at run time, we'd have to
duplicate parts of qapi-introspect.py in C. Unattractive.
* Let clients cache the output of query-qmp-schema.
It changes only on QEMU upgrades, i.e. rarely. Provide a command
query-qmp-schema-hash. Clients can have a cache indexed by hash,
and re-query the schema only when they don't have it cached. Even
simpler: put the hash in the QMP greeting.
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
2015-09-16 14:06:28 +03:00
|
|
|
member is optional if "default" is present. Currently, "default" can
|
|
|
|
only have value null. Other values are reserved for future
|
qapi-introspect: Document lack of sorting
qapi-code-gen.txt already claims that types, commands, and
events share a common namespace; set this in stone by further
documenting that our introspection output will never have
collisions with the same name tied to more than one meta-type.
Our largest QMP enum currently has 125 values, our largest
object type has 27 members, and the mean for each is less than
10. These sizes are small enough that the per-element overhead
of O(log n) binary searching probably outweighs the speed
possible with direct O(n) linear searching (a better algorithm
with more overhead will only beat a leaner naive algorithm only
as you scale to larger input sizes).
Arguably, the overall SchemaInfo array could be sorted by name;
there, we currently have 531 entities, large enough for a binary
search to be faster than linear. However, remember that we have
mutually-recursive types, which means there is no topological
ordering that will allow clients to learn all information about
that type in a single linear pass; thus clients will want to do
random access over the data, and they will probably read the
introspection output into a hashtable for O(1) lookup rather
than O(log n) binary searching, at which point, pre-sorting our
introspection output doesn't help the client.
It doesn't help that sorting can be subjective if you introduce
locales into the mix (I'm not experienced enough with Python
to know for sure, but at least it looks like it defaults to
sorting in the C locale even when run under a different locale).
And while our current introspection output is deterministic
(because we visit entities in a sorted order), we may want
to change that order in the future (such as using OrderedDict
to stick to .json declaration order).
For these reasons, we simply document that clients should not
rely on any particular order of items in introspection output.
And since it is now a documented part of the contract, we have
the freedom to later rearrange output if needed, without
worrying about breaking well-written clients.
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <1446791754-23823-13-git-send-email-eblake@redhat.com>
[Commit message tweaked]
Signed-off-by: Markus Armbruster <armbru@redhat.com>
2015-11-06 09:35:36 +03:00
|
|
|
extensions. The "members" array is in no particular order; clients
|
|
|
|
must search the entire object when learning whether a particular
|
|
|
|
member is supported.
|
qapi: New QMP command query-qmp-schema for QMP introspection
qapi/introspect.json defines the introspection schema. It's designed
for QMP introspection, but should do for similar uses, such as QGA.
The introspection schema does not reflect all the rules and
restrictions that apply to QAPI schemata. A valid QAPI schema has an
introspection value conforming to the introspection schema, but the
converse is not true.
Introspection lowers away a number of schema details, and makes
implicit things explicit:
* The built-in types are declared with their JSON type.
All integer types are mapped to 'int', because how many bits we use
internally is an implementation detail. It could be pressed into
external interface service as very approximate range information,
but that's a bad idea. If we need range information, we better do
it properly.
* Implicit type definitions are made explicit, and given
auto-generated names:
- Array types, named by appending "List" to the name of their
element type, like in generated C.
- The enumeration types implicitly defined by simple union types,
named by appending "Kind" to the name of their simple union type,
like in generated C.
- Types that don't occur in generated C. Their names start with ':'
so they don't clash with the user's names.
* All type references are by name.
* The struct and union types are generalized into an object type.
* Base types are flattened.
* Commands take a single argument and return a single result.
Dictionary argument or list result is an implicit type definition.
The empty object type is used when a command takes no arguments or
produces no results.
The argument is always of object type, but the introspection schema
doesn't reflect that.
The 'gen': false directive is omitted as implementation detail.
The 'success-response' directive is omitted as well for now, even
though it's not an implementation detail, because it's not used by
QMP.
* Events carry a single data value.
Implicit type definition and empty object type use, just like for
commands.
The value is of object type, but the introspection schema doesn't
reflect that.
* Types not used by commands or events are omitted.
Indirect use counts as use.
* Optional members have a default, which can only be null right now
Instead of a mandatory "optional" flag, we have an optional default.
No default means mandatory, default null means optional without
default value. Non-null is available for optional with default
(possible future extension).
* Clients should *not* look up types by name, because type names are
not ABI. Look up the command or event you're interested in, then
follow the references.
TODO Should we hide the type names to eliminate the temptation?
New generator scripts/qapi-introspect.py computes an introspection
value for its input, and generates a C variable holding it.
It can generate awfully long lines. Marked TODO.
A new test-qmp-input-visitor test case feeds its result for both
tests/qapi-schema/qapi-schema-test.json and qapi-schema.json to a
QmpInputVisitor to verify it actually conforms to the schema.
New QMP command query-qmp-schema takes its return value from that
variable. Its reply is some 85KiBytes for me right now.
If this turns out to be too much, we have a couple of options:
* We can use shorter names in the JSON. Not the QMP style.
* Optionally return the sub-schema for commands and events given as
arguments.
Right now qmp_query_schema() sends the string literal computed by
qmp-introspect.py. To compute sub-schema at run time, we'd have to
duplicate parts of qapi-introspect.py in C. Unattractive.
* Let clients cache the output of query-qmp-schema.
It changes only on QEMU upgrades, i.e. rarely. Provide a command
query-qmp-schema-hash. Clients can have a cache indexed by hash,
and re-query the schema only when they don't have it cached. Even
simpler: put the hash in the QMP greeting.
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
2015-09-16 14:06:28 +03:00
|
|
|
|
2021-07-21 02:56:19 +03:00
|
|
|
Example: the SchemaInfo for MyType from section `Struct types`_ ::
|
qapi: New QMP command query-qmp-schema for QMP introspection
qapi/introspect.json defines the introspection schema. It's designed
for QMP introspection, but should do for similar uses, such as QGA.
The introspection schema does not reflect all the rules and
restrictions that apply to QAPI schemata. A valid QAPI schema has an
introspection value conforming to the introspection schema, but the
converse is not true.
Introspection lowers away a number of schema details, and makes
implicit things explicit:
* The built-in types are declared with their JSON type.
All integer types are mapped to 'int', because how many bits we use
internally is an implementation detail. It could be pressed into
external interface service as very approximate range information,
but that's a bad idea. If we need range information, we better do
it properly.
* Implicit type definitions are made explicit, and given
auto-generated names:
- Array types, named by appending "List" to the name of their
element type, like in generated C.
- The enumeration types implicitly defined by simple union types,
named by appending "Kind" to the name of their simple union type,
like in generated C.
- Types that don't occur in generated C. Their names start with ':'
so they don't clash with the user's names.
* All type references are by name.
* The struct and union types are generalized into an object type.
* Base types are flattened.
* Commands take a single argument and return a single result.
Dictionary argument or list result is an implicit type definition.
The empty object type is used when a command takes no arguments or
produces no results.
The argument is always of object type, but the introspection schema
doesn't reflect that.
The 'gen': false directive is omitted as implementation detail.
The 'success-response' directive is omitted as well for now, even
though it's not an implementation detail, because it's not used by
QMP.
* Events carry a single data value.
Implicit type definition and empty object type use, just like for
commands.
The value is of object type, but the introspection schema doesn't
reflect that.
* Types not used by commands or events are omitted.
Indirect use counts as use.
* Optional members have a default, which can only be null right now
Instead of a mandatory "optional" flag, we have an optional default.
No default means mandatory, default null means optional without
default value. Non-null is available for optional with default
(possible future extension).
* Clients should *not* look up types by name, because type names are
not ABI. Look up the command or event you're interested in, then
follow the references.
TODO Should we hide the type names to eliminate the temptation?
New generator scripts/qapi-introspect.py computes an introspection
value for its input, and generates a C variable holding it.
It can generate awfully long lines. Marked TODO.
A new test-qmp-input-visitor test case feeds its result for both
tests/qapi-schema/qapi-schema-test.json and qapi-schema.json to a
QmpInputVisitor to verify it actually conforms to the schema.
New QMP command query-qmp-schema takes its return value from that
variable. Its reply is some 85KiBytes for me right now.
If this turns out to be too much, we have a couple of options:
* We can use shorter names in the JSON. Not the QMP style.
* Optionally return the sub-schema for commands and events given as
arguments.
Right now qmp_query_schema() sends the string literal computed by
qmp-introspect.py. To compute sub-schema at run time, we'd have to
duplicate parts of qapi-introspect.py in C. Unattractive.
* Let clients cache the output of query-qmp-schema.
It changes only on QEMU upgrades, i.e. rarely. Provide a command
query-qmp-schema-hash. Clients can have a cache indexed by hash,
and re-query the schema only when they don't have it cached. Even
simpler: put the hash in the QMP greeting.
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
2015-09-16 14:06:28 +03:00
|
|
|
|
|
|
|
{ "name": "MyType", "meta-type": "object",
|
|
|
|
"members": [
|
|
|
|
{ "name": "member1", "type": "str" },
|
|
|
|
{ "name": "member2", "type": "int" },
|
|
|
|
{ "name": "member3", "type": "str", "default": null } ] }
|
|
|
|
|
2020-03-17 14:54:29 +03:00
|
|
|
"features" exposes the command's feature strings as a JSON array of
|
|
|
|
strings.
|
|
|
|
|
2021-07-21 02:56:19 +03:00
|
|
|
Example: the SchemaInfo for TestType from section Features_::
|
2020-03-17 14:54:29 +03:00
|
|
|
|
|
|
|
{ "name": "TestType", "meta-type": "object",
|
|
|
|
"members": [
|
|
|
|
{ "name": "number", "type": "int" } ],
|
|
|
|
"features": ["allow-negative-numbers"] }
|
|
|
|
|
qapi: New QMP command query-qmp-schema for QMP introspection
qapi/introspect.json defines the introspection schema. It's designed
for QMP introspection, but should do for similar uses, such as QGA.
The introspection schema does not reflect all the rules and
restrictions that apply to QAPI schemata. A valid QAPI schema has an
introspection value conforming to the introspection schema, but the
converse is not true.
Introspection lowers away a number of schema details, and makes
implicit things explicit:
* The built-in types are declared with their JSON type.
All integer types are mapped to 'int', because how many bits we use
internally is an implementation detail. It could be pressed into
external interface service as very approximate range information,
but that's a bad idea. If we need range information, we better do
it properly.
* Implicit type definitions are made explicit, and given
auto-generated names:
- Array types, named by appending "List" to the name of their
element type, like in generated C.
- The enumeration types implicitly defined by simple union types,
named by appending "Kind" to the name of their simple union type,
like in generated C.
- Types that don't occur in generated C. Their names start with ':'
so they don't clash with the user's names.
* All type references are by name.
* The struct and union types are generalized into an object type.
* Base types are flattened.
* Commands take a single argument and return a single result.
Dictionary argument or list result is an implicit type definition.
The empty object type is used when a command takes no arguments or
produces no results.
The argument is always of object type, but the introspection schema
doesn't reflect that.
The 'gen': false directive is omitted as implementation detail.
The 'success-response' directive is omitted as well for now, even
though it's not an implementation detail, because it's not used by
QMP.
* Events carry a single data value.
Implicit type definition and empty object type use, just like for
commands.
The value is of object type, but the introspection schema doesn't
reflect that.
* Types not used by commands or events are omitted.
Indirect use counts as use.
* Optional members have a default, which can only be null right now
Instead of a mandatory "optional" flag, we have an optional default.
No default means mandatory, default null means optional without
default value. Non-null is available for optional with default
(possible future extension).
* Clients should *not* look up types by name, because type names are
not ABI. Look up the command or event you're interested in, then
follow the references.
TODO Should we hide the type names to eliminate the temptation?
New generator scripts/qapi-introspect.py computes an introspection
value for its input, and generates a C variable holding it.
It can generate awfully long lines. Marked TODO.
A new test-qmp-input-visitor test case feeds its result for both
tests/qapi-schema/qapi-schema-test.json and qapi-schema.json to a
QmpInputVisitor to verify it actually conforms to the schema.
New QMP command query-qmp-schema takes its return value from that
variable. Its reply is some 85KiBytes for me right now.
If this turns out to be too much, we have a couple of options:
* We can use shorter names in the JSON. Not the QMP style.
* Optionally return the sub-schema for commands and events given as
arguments.
Right now qmp_query_schema() sends the string literal computed by
qmp-introspect.py. To compute sub-schema at run time, we'd have to
duplicate parts of qapi-introspect.py in C. Unattractive.
* Let clients cache the output of query-qmp-schema.
It changes only on QEMU upgrades, i.e. rarely. Provide a command
query-qmp-schema-hash. Clients can have a cache indexed by hash,
and re-query the schema only when they don't have it cached. Even
simpler: put the hash in the QMP greeting.
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
2015-09-16 14:06:28 +03:00
|
|
|
"tag" is the name of the common member serving as type tag.
|
|
|
|
"variants" is a JSON array describing the object's variant members.
|
|
|
|
Each element is a JSON object with members "case" (the value of type
|
|
|
|
tag this element applies to) and "type" (the name of an object type
|
qapi-introspect: Document lack of sorting
qapi-code-gen.txt already claims that types, commands, and
events share a common namespace; set this in stone by further
documenting that our introspection output will never have
collisions with the same name tied to more than one meta-type.
Our largest QMP enum currently has 125 values, our largest
object type has 27 members, and the mean for each is less than
10. These sizes are small enough that the per-element overhead
of O(log n) binary searching probably outweighs the speed
possible with direct O(n) linear searching (a better algorithm
with more overhead will only beat a leaner naive algorithm only
as you scale to larger input sizes).
Arguably, the overall SchemaInfo array could be sorted by name;
there, we currently have 531 entities, large enough for a binary
search to be faster than linear. However, remember that we have
mutually-recursive types, which means there is no topological
ordering that will allow clients to learn all information about
that type in a single linear pass; thus clients will want to do
random access over the data, and they will probably read the
introspection output into a hashtable for O(1) lookup rather
than O(log n) binary searching, at which point, pre-sorting our
introspection output doesn't help the client.
It doesn't help that sorting can be subjective if you introduce
locales into the mix (I'm not experienced enough with Python
to know for sure, but at least it looks like it defaults to
sorting in the C locale even when run under a different locale).
And while our current introspection output is deterministic
(because we visit entities in a sorted order), we may want
to change that order in the future (such as using OrderedDict
to stick to .json declaration order).
For these reasons, we simply document that clients should not
rely on any particular order of items in introspection output.
And since it is now a documented part of the contract, we have
the freedom to later rearrange output if needed, without
worrying about breaking well-written clients.
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <1446791754-23823-13-git-send-email-eblake@redhat.com>
[Commit message tweaked]
Signed-off-by: Markus Armbruster <armbru@redhat.com>
2015-11-06 09:35:36 +03:00
|
|
|
that provides the variant members for this type tag value). The
|
|
|
|
"variants" array is in no particular order, and is not guaranteed to
|
|
|
|
list cases in the same order as the corresponding "tag" enum type.
|
qapi: New QMP command query-qmp-schema for QMP introspection
qapi/introspect.json defines the introspection schema. It's designed
for QMP introspection, but should do for similar uses, such as QGA.
The introspection schema does not reflect all the rules and
restrictions that apply to QAPI schemata. A valid QAPI schema has an
introspection value conforming to the introspection schema, but the
converse is not true.
Introspection lowers away a number of schema details, and makes
implicit things explicit:
* The built-in types are declared with their JSON type.
All integer types are mapped to 'int', because how many bits we use
internally is an implementation detail. It could be pressed into
external interface service as very approximate range information,
but that's a bad idea. If we need range information, we better do
it properly.
* Implicit type definitions are made explicit, and given
auto-generated names:
- Array types, named by appending "List" to the name of their
element type, like in generated C.
- The enumeration types implicitly defined by simple union types,
named by appending "Kind" to the name of their simple union type,
like in generated C.
- Types that don't occur in generated C. Their names start with ':'
so they don't clash with the user's names.
* All type references are by name.
* The struct and union types are generalized into an object type.
* Base types are flattened.
* Commands take a single argument and return a single result.
Dictionary argument or list result is an implicit type definition.
The empty object type is used when a command takes no arguments or
produces no results.
The argument is always of object type, but the introspection schema
doesn't reflect that.
The 'gen': false directive is omitted as implementation detail.
The 'success-response' directive is omitted as well for now, even
though it's not an implementation detail, because it's not used by
QMP.
* Events carry a single data value.
Implicit type definition and empty object type use, just like for
commands.
The value is of object type, but the introspection schema doesn't
reflect that.
* Types not used by commands or events are omitted.
Indirect use counts as use.
* Optional members have a default, which can only be null right now
Instead of a mandatory "optional" flag, we have an optional default.
No default means mandatory, default null means optional without
default value. Non-null is available for optional with default
(possible future extension).
* Clients should *not* look up types by name, because type names are
not ABI. Look up the command or event you're interested in, then
follow the references.
TODO Should we hide the type names to eliminate the temptation?
New generator scripts/qapi-introspect.py computes an introspection
value for its input, and generates a C variable holding it.
It can generate awfully long lines. Marked TODO.
A new test-qmp-input-visitor test case feeds its result for both
tests/qapi-schema/qapi-schema-test.json and qapi-schema.json to a
QmpInputVisitor to verify it actually conforms to the schema.
New QMP command query-qmp-schema takes its return value from that
variable. Its reply is some 85KiBytes for me right now.
If this turns out to be too much, we have a couple of options:
* We can use shorter names in the JSON. Not the QMP style.
* Optionally return the sub-schema for commands and events given as
arguments.
Right now qmp_query_schema() sends the string literal computed by
qmp-introspect.py. To compute sub-schema at run time, we'd have to
duplicate parts of qapi-introspect.py in C. Unattractive.
* Let clients cache the output of query-qmp-schema.
It changes only on QEMU upgrades, i.e. rarely. Provide a command
query-qmp-schema-hash. Clients can have a cache indexed by hash,
and re-query the schema only when they don't have it cached. Even
simpler: put the hash in the QMP greeting.
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
2015-09-16 14:06:28 +03:00
|
|
|
|
2021-09-17 17:31:32 +03:00
|
|
|
Example: the SchemaInfo for union BlockdevOptions from section
|
2021-07-21 02:56:19 +03:00
|
|
|
`Union types`_ ::
|
qapi: New QMP command query-qmp-schema for QMP introspection
qapi/introspect.json defines the introspection schema. It's designed
for QMP introspection, but should do for similar uses, such as QGA.
The introspection schema does not reflect all the rules and
restrictions that apply to QAPI schemata. A valid QAPI schema has an
introspection value conforming to the introspection schema, but the
converse is not true.
Introspection lowers away a number of schema details, and makes
implicit things explicit:
* The built-in types are declared with their JSON type.
All integer types are mapped to 'int', because how many bits we use
internally is an implementation detail. It could be pressed into
external interface service as very approximate range information,
but that's a bad idea. If we need range information, we better do
it properly.
* Implicit type definitions are made explicit, and given
auto-generated names:
- Array types, named by appending "List" to the name of their
element type, like in generated C.
- The enumeration types implicitly defined by simple union types,
named by appending "Kind" to the name of their simple union type,
like in generated C.
- Types that don't occur in generated C. Their names start with ':'
so they don't clash with the user's names.
* All type references are by name.
* The struct and union types are generalized into an object type.
* Base types are flattened.
* Commands take a single argument and return a single result.
Dictionary argument or list result is an implicit type definition.
The empty object type is used when a command takes no arguments or
produces no results.
The argument is always of object type, but the introspection schema
doesn't reflect that.
The 'gen': false directive is omitted as implementation detail.
The 'success-response' directive is omitted as well for now, even
though it's not an implementation detail, because it's not used by
QMP.
* Events carry a single data value.
Implicit type definition and empty object type use, just like for
commands.
The value is of object type, but the introspection schema doesn't
reflect that.
* Types not used by commands or events are omitted.
Indirect use counts as use.
* Optional members have a default, which can only be null right now
Instead of a mandatory "optional" flag, we have an optional default.
No default means mandatory, default null means optional without
default value. Non-null is available for optional with default
(possible future extension).
* Clients should *not* look up types by name, because type names are
not ABI. Look up the command or event you're interested in, then
follow the references.
TODO Should we hide the type names to eliminate the temptation?
New generator scripts/qapi-introspect.py computes an introspection
value for its input, and generates a C variable holding it.
It can generate awfully long lines. Marked TODO.
A new test-qmp-input-visitor test case feeds its result for both
tests/qapi-schema/qapi-schema-test.json and qapi-schema.json to a
QmpInputVisitor to verify it actually conforms to the schema.
New QMP command query-qmp-schema takes its return value from that
variable. Its reply is some 85KiBytes for me right now.
If this turns out to be too much, we have a couple of options:
* We can use shorter names in the JSON. Not the QMP style.
* Optionally return the sub-schema for commands and events given as
arguments.
Right now qmp_query_schema() sends the string literal computed by
qmp-introspect.py. To compute sub-schema at run time, we'd have to
duplicate parts of qapi-introspect.py in C. Unattractive.
* Let clients cache the output of query-qmp-schema.
It changes only on QEMU upgrades, i.e. rarely. Provide a command
query-qmp-schema-hash. Clients can have a cache indexed by hash,
and re-query the schema only when they don't have it cached. Even
simpler: put the hash in the QMP greeting.
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
2015-09-16 14:06:28 +03:00
|
|
|
|
|
|
|
{ "name": "BlockdevOptions", "meta-type": "object",
|
|
|
|
"members": [
|
|
|
|
{ "name": "driver", "type": "BlockdevDriver" },
|
2016-03-18 01:48:38 +03:00
|
|
|
{ "name": "read-only", "type": "bool", "default": null } ],
|
qapi: New QMP command query-qmp-schema for QMP introspection
qapi/introspect.json defines the introspection schema. It's designed
for QMP introspection, but should do for similar uses, such as QGA.
The introspection schema does not reflect all the rules and
restrictions that apply to QAPI schemata. A valid QAPI schema has an
introspection value conforming to the introspection schema, but the
converse is not true.
Introspection lowers away a number of schema details, and makes
implicit things explicit:
* The built-in types are declared with their JSON type.
All integer types are mapped to 'int', because how many bits we use
internally is an implementation detail. It could be pressed into
external interface service as very approximate range information,
but that's a bad idea. If we need range information, we better do
it properly.
* Implicit type definitions are made explicit, and given
auto-generated names:
- Array types, named by appending "List" to the name of their
element type, like in generated C.
- The enumeration types implicitly defined by simple union types,
named by appending "Kind" to the name of their simple union type,
like in generated C.
- Types that don't occur in generated C. Their names start with ':'
so they don't clash with the user's names.
* All type references are by name.
* The struct and union types are generalized into an object type.
* Base types are flattened.
* Commands take a single argument and return a single result.
Dictionary argument or list result is an implicit type definition.
The empty object type is used when a command takes no arguments or
produces no results.
The argument is always of object type, but the introspection schema
doesn't reflect that.
The 'gen': false directive is omitted as implementation detail.
The 'success-response' directive is omitted as well for now, even
though it's not an implementation detail, because it's not used by
QMP.
* Events carry a single data value.
Implicit type definition and empty object type use, just like for
commands.
The value is of object type, but the introspection schema doesn't
reflect that.
* Types not used by commands or events are omitted.
Indirect use counts as use.
* Optional members have a default, which can only be null right now
Instead of a mandatory "optional" flag, we have an optional default.
No default means mandatory, default null means optional without
default value. Non-null is available for optional with default
(possible future extension).
* Clients should *not* look up types by name, because type names are
not ABI. Look up the command or event you're interested in, then
follow the references.
TODO Should we hide the type names to eliminate the temptation?
New generator scripts/qapi-introspect.py computes an introspection
value for its input, and generates a C variable holding it.
It can generate awfully long lines. Marked TODO.
A new test-qmp-input-visitor test case feeds its result for both
tests/qapi-schema/qapi-schema-test.json and qapi-schema.json to a
QmpInputVisitor to verify it actually conforms to the schema.
New QMP command query-qmp-schema takes its return value from that
variable. Its reply is some 85KiBytes for me right now.
If this turns out to be too much, we have a couple of options:
* We can use shorter names in the JSON. Not the QMP style.
* Optionally return the sub-schema for commands and events given as
arguments.
Right now qmp_query_schema() sends the string literal computed by
qmp-introspect.py. To compute sub-schema at run time, we'd have to
duplicate parts of qapi-introspect.py in C. Unattractive.
* Let clients cache the output of query-qmp-schema.
It changes only on QEMU upgrades, i.e. rarely. Provide a command
query-qmp-schema-hash. Clients can have a cache indexed by hash,
and re-query the schema only when they don't have it cached. Even
simpler: put the hash in the QMP greeting.
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
2015-09-16 14:06:28 +03:00
|
|
|
"tag": "driver",
|
|
|
|
"variants": [
|
2016-03-18 01:48:38 +03:00
|
|
|
{ "case": "file", "type": "BlockdevOptionsFile" },
|
|
|
|
{ "case": "qcow2", "type": "BlockdevOptionsQcow2" } ] }
|
qapi: New QMP command query-qmp-schema for QMP introspection
qapi/introspect.json defines the introspection schema. It's designed
for QMP introspection, but should do for similar uses, such as QGA.
The introspection schema does not reflect all the rules and
restrictions that apply to QAPI schemata. A valid QAPI schema has an
introspection value conforming to the introspection schema, but the
converse is not true.
Introspection lowers away a number of schema details, and makes
implicit things explicit:
* The built-in types are declared with their JSON type.
All integer types are mapped to 'int', because how many bits we use
internally is an implementation detail. It could be pressed into
external interface service as very approximate range information,
but that's a bad idea. If we need range information, we better do
it properly.
* Implicit type definitions are made explicit, and given
auto-generated names:
- Array types, named by appending "List" to the name of their
element type, like in generated C.
- The enumeration types implicitly defined by simple union types,
named by appending "Kind" to the name of their simple union type,
like in generated C.
- Types that don't occur in generated C. Their names start with ':'
so they don't clash with the user's names.
* All type references are by name.
* The struct and union types are generalized into an object type.
* Base types are flattened.
* Commands take a single argument and return a single result.
Dictionary argument or list result is an implicit type definition.
The empty object type is used when a command takes no arguments or
produces no results.
The argument is always of object type, but the introspection schema
doesn't reflect that.
The 'gen': false directive is omitted as implementation detail.
The 'success-response' directive is omitted as well for now, even
though it's not an implementation detail, because it's not used by
QMP.
* Events carry a single data value.
Implicit type definition and empty object type use, just like for
commands.
The value is of object type, but the introspection schema doesn't
reflect that.
* Types not used by commands or events are omitted.
Indirect use counts as use.
* Optional members have a default, which can only be null right now
Instead of a mandatory "optional" flag, we have an optional default.
No default means mandatory, default null means optional without
default value. Non-null is available for optional with default
(possible future extension).
* Clients should *not* look up types by name, because type names are
not ABI. Look up the command or event you're interested in, then
follow the references.
TODO Should we hide the type names to eliminate the temptation?
New generator scripts/qapi-introspect.py computes an introspection
value for its input, and generates a C variable holding it.
It can generate awfully long lines. Marked TODO.
A new test-qmp-input-visitor test case feeds its result for both
tests/qapi-schema/qapi-schema-test.json and qapi-schema.json to a
QmpInputVisitor to verify it actually conforms to the schema.
New QMP command query-qmp-schema takes its return value from that
variable. Its reply is some 85KiBytes for me right now.
If this turns out to be too much, we have a couple of options:
* We can use shorter names in the JSON. Not the QMP style.
* Optionally return the sub-schema for commands and events given as
arguments.
Right now qmp_query_schema() sends the string literal computed by
qmp-introspect.py. To compute sub-schema at run time, we'd have to
duplicate parts of qapi-introspect.py in C. Unattractive.
* Let clients cache the output of query-qmp-schema.
It changes only on QEMU upgrades, i.e. rarely. Provide a command
query-qmp-schema-hash. Clients can have a cache indexed by hash,
and re-query the schema only when they don't have it cached. Even
simpler: put the hash in the QMP greeting.
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
2015-09-16 14:06:28 +03:00
|
|
|
|
|
|
|
Note that base types are "flattened": its members are included in the
|
|
|
|
"members" array.
|
|
|
|
|
|
|
|
The SchemaInfo for an alternate type has meta-type "alternate", and
|
|
|
|
variant member "members". "members" is a JSON array. Each element is
|
|
|
|
a JSON object with member "type", which names a type. Values of the
|
qapi-introspect: Document lack of sorting
qapi-code-gen.txt already claims that types, commands, and
events share a common namespace; set this in stone by further
documenting that our introspection output will never have
collisions with the same name tied to more than one meta-type.
Our largest QMP enum currently has 125 values, our largest
object type has 27 members, and the mean for each is less than
10. These sizes are small enough that the per-element overhead
of O(log n) binary searching probably outweighs the speed
possible with direct O(n) linear searching (a better algorithm
with more overhead will only beat a leaner naive algorithm only
as you scale to larger input sizes).
Arguably, the overall SchemaInfo array could be sorted by name;
there, we currently have 531 entities, large enough for a binary
search to be faster than linear. However, remember that we have
mutually-recursive types, which means there is no topological
ordering that will allow clients to learn all information about
that type in a single linear pass; thus clients will want to do
random access over the data, and they will probably read the
introspection output into a hashtable for O(1) lookup rather
than O(log n) binary searching, at which point, pre-sorting our
introspection output doesn't help the client.
It doesn't help that sorting can be subjective if you introduce
locales into the mix (I'm not experienced enough with Python
to know for sure, but at least it looks like it defaults to
sorting in the C locale even when run under a different locale).
And while our current introspection output is deterministic
(because we visit entities in a sorted order), we may want
to change that order in the future (such as using OrderedDict
to stick to .json declaration order).
For these reasons, we simply document that clients should not
rely on any particular order of items in introspection output.
And since it is now a documented part of the contract, we have
the freedom to later rearrange output if needed, without
worrying about breaking well-written clients.
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <1446791754-23823-13-git-send-email-eblake@redhat.com>
[Commit message tweaked]
Signed-off-by: Markus Armbruster <armbru@redhat.com>
2015-11-06 09:35:36 +03:00
|
|
|
alternate type conform to exactly one of its member types. There is
|
|
|
|
no guarantee on the order in which "members" will be listed.
|
qapi: New QMP command query-qmp-schema for QMP introspection
qapi/introspect.json defines the introspection schema. It's designed
for QMP introspection, but should do for similar uses, such as QGA.
The introspection schema does not reflect all the rules and
restrictions that apply to QAPI schemata. A valid QAPI schema has an
introspection value conforming to the introspection schema, but the
converse is not true.
Introspection lowers away a number of schema details, and makes
implicit things explicit:
* The built-in types are declared with their JSON type.
All integer types are mapped to 'int', because how many bits we use
internally is an implementation detail. It could be pressed into
external interface service as very approximate range information,
but that's a bad idea. If we need range information, we better do
it properly.
* Implicit type definitions are made explicit, and given
auto-generated names:
- Array types, named by appending "List" to the name of their
element type, like in generated C.
- The enumeration types implicitly defined by simple union types,
named by appending "Kind" to the name of their simple union type,
like in generated C.
- Types that don't occur in generated C. Their names start with ':'
so they don't clash with the user's names.
* All type references are by name.
* The struct and union types are generalized into an object type.
* Base types are flattened.
* Commands take a single argument and return a single result.
Dictionary argument or list result is an implicit type definition.
The empty object type is used when a command takes no arguments or
produces no results.
The argument is always of object type, but the introspection schema
doesn't reflect that.
The 'gen': false directive is omitted as implementation detail.
The 'success-response' directive is omitted as well for now, even
though it's not an implementation detail, because it's not used by
QMP.
* Events carry a single data value.
Implicit type definition and empty object type use, just like for
commands.
The value is of object type, but the introspection schema doesn't
reflect that.
* Types not used by commands or events are omitted.
Indirect use counts as use.
* Optional members have a default, which can only be null right now
Instead of a mandatory "optional" flag, we have an optional default.
No default means mandatory, default null means optional without
default value. Non-null is available for optional with default
(possible future extension).
* Clients should *not* look up types by name, because type names are
not ABI. Look up the command or event you're interested in, then
follow the references.
TODO Should we hide the type names to eliminate the temptation?
New generator scripts/qapi-introspect.py computes an introspection
value for its input, and generates a C variable holding it.
It can generate awfully long lines. Marked TODO.
A new test-qmp-input-visitor test case feeds its result for both
tests/qapi-schema/qapi-schema-test.json and qapi-schema.json to a
QmpInputVisitor to verify it actually conforms to the schema.
New QMP command query-qmp-schema takes its return value from that
variable. Its reply is some 85KiBytes for me right now.
If this turns out to be too much, we have a couple of options:
* We can use shorter names in the JSON. Not the QMP style.
* Optionally return the sub-schema for commands and events given as
arguments.
Right now qmp_query_schema() sends the string literal computed by
qmp-introspect.py. To compute sub-schema at run time, we'd have to
duplicate parts of qapi-introspect.py in C. Unattractive.
* Let clients cache the output of query-qmp-schema.
It changes only on QEMU upgrades, i.e. rarely. Provide a command
query-qmp-schema-hash. Clients can have a cache indexed by hash,
and re-query the schema only when they don't have it cached. Even
simpler: put the hash in the QMP greeting.
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
2015-09-16 14:06:28 +03:00
|
|
|
|
2021-07-21 02:56:19 +03:00
|
|
|
Example: the SchemaInfo for BlockdevRef from section `Alternate types`_ ::
|
qapi: New QMP command query-qmp-schema for QMP introspection
qapi/introspect.json defines the introspection schema. It's designed
for QMP introspection, but should do for similar uses, such as QGA.
The introspection schema does not reflect all the rules and
restrictions that apply to QAPI schemata. A valid QAPI schema has an
introspection value conforming to the introspection schema, but the
converse is not true.
Introspection lowers away a number of schema details, and makes
implicit things explicit:
* The built-in types are declared with their JSON type.
All integer types are mapped to 'int', because how many bits we use
internally is an implementation detail. It could be pressed into
external interface service as very approximate range information,
but that's a bad idea. If we need range information, we better do
it properly.
* Implicit type definitions are made explicit, and given
auto-generated names:
- Array types, named by appending "List" to the name of their
element type, like in generated C.
- The enumeration types implicitly defined by simple union types,
named by appending "Kind" to the name of their simple union type,
like in generated C.
- Types that don't occur in generated C. Their names start with ':'
so they don't clash with the user's names.
* All type references are by name.
* The struct and union types are generalized into an object type.
* Base types are flattened.
* Commands take a single argument and return a single result.
Dictionary argument or list result is an implicit type definition.
The empty object type is used when a command takes no arguments or
produces no results.
The argument is always of object type, but the introspection schema
doesn't reflect that.
The 'gen': false directive is omitted as implementation detail.
The 'success-response' directive is omitted as well for now, even
though it's not an implementation detail, because it's not used by
QMP.
* Events carry a single data value.
Implicit type definition and empty object type use, just like for
commands.
The value is of object type, but the introspection schema doesn't
reflect that.
* Types not used by commands or events are omitted.
Indirect use counts as use.
* Optional members have a default, which can only be null right now
Instead of a mandatory "optional" flag, we have an optional default.
No default means mandatory, default null means optional without
default value. Non-null is available for optional with default
(possible future extension).
* Clients should *not* look up types by name, because type names are
not ABI. Look up the command or event you're interested in, then
follow the references.
TODO Should we hide the type names to eliminate the temptation?
New generator scripts/qapi-introspect.py computes an introspection
value for its input, and generates a C variable holding it.
It can generate awfully long lines. Marked TODO.
A new test-qmp-input-visitor test case feeds its result for both
tests/qapi-schema/qapi-schema-test.json and qapi-schema.json to a
QmpInputVisitor to verify it actually conforms to the schema.
New QMP command query-qmp-schema takes its return value from that
variable. Its reply is some 85KiBytes for me right now.
If this turns out to be too much, we have a couple of options:
* We can use shorter names in the JSON. Not the QMP style.
* Optionally return the sub-schema for commands and events given as
arguments.
Right now qmp_query_schema() sends the string literal computed by
qmp-introspect.py. To compute sub-schema at run time, we'd have to
duplicate parts of qapi-introspect.py in C. Unattractive.
* Let clients cache the output of query-qmp-schema.
It changes only on QEMU upgrades, i.e. rarely. Provide a command
query-qmp-schema-hash. Clients can have a cache indexed by hash,
and re-query the schema only when they don't have it cached. Even
simpler: put the hash in the QMP greeting.
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
2015-09-16 14:06:28 +03:00
|
|
|
|
2016-03-18 01:48:38 +03:00
|
|
|
{ "name": "BlockdevRef", "meta-type": "alternate",
|
qapi: New QMP command query-qmp-schema for QMP introspection
qapi/introspect.json defines the introspection schema. It's designed
for QMP introspection, but should do for similar uses, such as QGA.
The introspection schema does not reflect all the rules and
restrictions that apply to QAPI schemata. A valid QAPI schema has an
introspection value conforming to the introspection schema, but the
converse is not true.
Introspection lowers away a number of schema details, and makes
implicit things explicit:
* The built-in types are declared with their JSON type.
All integer types are mapped to 'int', because how many bits we use
internally is an implementation detail. It could be pressed into
external interface service as very approximate range information,
but that's a bad idea. If we need range information, we better do
it properly.
* Implicit type definitions are made explicit, and given
auto-generated names:
- Array types, named by appending "List" to the name of their
element type, like in generated C.
- The enumeration types implicitly defined by simple union types,
named by appending "Kind" to the name of their simple union type,
like in generated C.
- Types that don't occur in generated C. Their names start with ':'
so they don't clash with the user's names.
* All type references are by name.
* The struct and union types are generalized into an object type.
* Base types are flattened.
* Commands take a single argument and return a single result.
Dictionary argument or list result is an implicit type definition.
The empty object type is used when a command takes no arguments or
produces no results.
The argument is always of object type, but the introspection schema
doesn't reflect that.
The 'gen': false directive is omitted as implementation detail.
The 'success-response' directive is omitted as well for now, even
though it's not an implementation detail, because it's not used by
QMP.
* Events carry a single data value.
Implicit type definition and empty object type use, just like for
commands.
The value is of object type, but the introspection schema doesn't
reflect that.
* Types not used by commands or events are omitted.
Indirect use counts as use.
* Optional members have a default, which can only be null right now
Instead of a mandatory "optional" flag, we have an optional default.
No default means mandatory, default null means optional without
default value. Non-null is available for optional with default
(possible future extension).
* Clients should *not* look up types by name, because type names are
not ABI. Look up the command or event you're interested in, then
follow the references.
TODO Should we hide the type names to eliminate the temptation?
New generator scripts/qapi-introspect.py computes an introspection
value for its input, and generates a C variable holding it.
It can generate awfully long lines. Marked TODO.
A new test-qmp-input-visitor test case feeds its result for both
tests/qapi-schema/qapi-schema-test.json and qapi-schema.json to a
QmpInputVisitor to verify it actually conforms to the schema.
New QMP command query-qmp-schema takes its return value from that
variable. Its reply is some 85KiBytes for me right now.
If this turns out to be too much, we have a couple of options:
* We can use shorter names in the JSON. Not the QMP style.
* Optionally return the sub-schema for commands and events given as
arguments.
Right now qmp_query_schema() sends the string literal computed by
qmp-introspect.py. To compute sub-schema at run time, we'd have to
duplicate parts of qapi-introspect.py in C. Unattractive.
* Let clients cache the output of query-qmp-schema.
It changes only on QEMU upgrades, i.e. rarely. Provide a command
query-qmp-schema-hash. Clients can have a cache indexed by hash,
and re-query the schema only when they don't have it cached. Even
simpler: put the hash in the QMP greeting.
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
2015-09-16 14:06:28 +03:00
|
|
|
"members": [
|
|
|
|
{ "type": "BlockdevOptions" },
|
|
|
|
{ "type": "str" } ] }
|
|
|
|
|
|
|
|
The SchemaInfo for an array type has meta-type "array", and variant
|
|
|
|
member "element-type", which names the array's element type. Array
|
2015-11-06 09:35:35 +03:00
|
|
|
types are implicitly defined. For convenience, the array's name may
|
|
|
|
resemble the element type; however, clients should examine member
|
|
|
|
"element-type" instead of making assumptions based on parsing member
|
|
|
|
"name".
|
qapi: New QMP command query-qmp-schema for QMP introspection
qapi/introspect.json defines the introspection schema. It's designed
for QMP introspection, but should do for similar uses, such as QGA.
The introspection schema does not reflect all the rules and
restrictions that apply to QAPI schemata. A valid QAPI schema has an
introspection value conforming to the introspection schema, but the
converse is not true.
Introspection lowers away a number of schema details, and makes
implicit things explicit:
* The built-in types are declared with their JSON type.
All integer types are mapped to 'int', because how many bits we use
internally is an implementation detail. It could be pressed into
external interface service as very approximate range information,
but that's a bad idea. If we need range information, we better do
it properly.
* Implicit type definitions are made explicit, and given
auto-generated names:
- Array types, named by appending "List" to the name of their
element type, like in generated C.
- The enumeration types implicitly defined by simple union types,
named by appending "Kind" to the name of their simple union type,
like in generated C.
- Types that don't occur in generated C. Their names start with ':'
so they don't clash with the user's names.
* All type references are by name.
* The struct and union types are generalized into an object type.
* Base types are flattened.
* Commands take a single argument and return a single result.
Dictionary argument or list result is an implicit type definition.
The empty object type is used when a command takes no arguments or
produces no results.
The argument is always of object type, but the introspection schema
doesn't reflect that.
The 'gen': false directive is omitted as implementation detail.
The 'success-response' directive is omitted as well for now, even
though it's not an implementation detail, because it's not used by
QMP.
* Events carry a single data value.
Implicit type definition and empty object type use, just like for
commands.
The value is of object type, but the introspection schema doesn't
reflect that.
* Types not used by commands or events are omitted.
Indirect use counts as use.
* Optional members have a default, which can only be null right now
Instead of a mandatory "optional" flag, we have an optional default.
No default means mandatory, default null means optional without
default value. Non-null is available for optional with default
(possible future extension).
* Clients should *not* look up types by name, because type names are
not ABI. Look up the command or event you're interested in, then
follow the references.
TODO Should we hide the type names to eliminate the temptation?
New generator scripts/qapi-introspect.py computes an introspection
value for its input, and generates a C variable holding it.
It can generate awfully long lines. Marked TODO.
A new test-qmp-input-visitor test case feeds its result for both
tests/qapi-schema/qapi-schema-test.json and qapi-schema.json to a
QmpInputVisitor to verify it actually conforms to the schema.
New QMP command query-qmp-schema takes its return value from that
variable. Its reply is some 85KiBytes for me right now.
If this turns out to be too much, we have a couple of options:
* We can use shorter names in the JSON. Not the QMP style.
* Optionally return the sub-schema for commands and events given as
arguments.
Right now qmp_query_schema() sends the string literal computed by
qmp-introspect.py. To compute sub-schema at run time, we'd have to
duplicate parts of qapi-introspect.py in C. Unattractive.
* Let clients cache the output of query-qmp-schema.
It changes only on QEMU upgrades, i.e. rarely. Provide a command
query-qmp-schema-hash. Clients can have a cache indexed by hash,
and re-query the schema only when they don't have it cached. Even
simpler: put the hash in the QMP greeting.
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
2015-09-16 14:06:28 +03:00
|
|
|
|
2021-07-21 02:56:17 +03:00
|
|
|
Example: the SchemaInfo for ['str'] ::
|
qapi: New QMP command query-qmp-schema for QMP introspection
qapi/introspect.json defines the introspection schema. It's designed
for QMP introspection, but should do for similar uses, such as QGA.
The introspection schema does not reflect all the rules and
restrictions that apply to QAPI schemata. A valid QAPI schema has an
introspection value conforming to the introspection schema, but the
converse is not true.
Introspection lowers away a number of schema details, and makes
implicit things explicit:
* The built-in types are declared with their JSON type.
All integer types are mapped to 'int', because how many bits we use
internally is an implementation detail. It could be pressed into
external interface service as very approximate range information,
but that's a bad idea. If we need range information, we better do
it properly.
* Implicit type definitions are made explicit, and given
auto-generated names:
- Array types, named by appending "List" to the name of their
element type, like in generated C.
- The enumeration types implicitly defined by simple union types,
named by appending "Kind" to the name of their simple union type,
like in generated C.
- Types that don't occur in generated C. Their names start with ':'
so they don't clash with the user's names.
* All type references are by name.
* The struct and union types are generalized into an object type.
* Base types are flattened.
* Commands take a single argument and return a single result.
Dictionary argument or list result is an implicit type definition.
The empty object type is used when a command takes no arguments or
produces no results.
The argument is always of object type, but the introspection schema
doesn't reflect that.
The 'gen': false directive is omitted as implementation detail.
The 'success-response' directive is omitted as well for now, even
though it's not an implementation detail, because it's not used by
QMP.
* Events carry a single data value.
Implicit type definition and empty object type use, just like for
commands.
The value is of object type, but the introspection schema doesn't
reflect that.
* Types not used by commands or events are omitted.
Indirect use counts as use.
* Optional members have a default, which can only be null right now
Instead of a mandatory "optional" flag, we have an optional default.
No default means mandatory, default null means optional without
default value. Non-null is available for optional with default
(possible future extension).
* Clients should *not* look up types by name, because type names are
not ABI. Look up the command or event you're interested in, then
follow the references.
TODO Should we hide the type names to eliminate the temptation?
New generator scripts/qapi-introspect.py computes an introspection
value for its input, and generates a C variable holding it.
It can generate awfully long lines. Marked TODO.
A new test-qmp-input-visitor test case feeds its result for both
tests/qapi-schema/qapi-schema-test.json and qapi-schema.json to a
QmpInputVisitor to verify it actually conforms to the schema.
New QMP command query-qmp-schema takes its return value from that
variable. Its reply is some 85KiBytes for me right now.
If this turns out to be too much, we have a couple of options:
* We can use shorter names in the JSON. Not the QMP style.
* Optionally return the sub-schema for commands and events given as
arguments.
Right now qmp_query_schema() sends the string literal computed by
qmp-introspect.py. To compute sub-schema at run time, we'd have to
duplicate parts of qapi-introspect.py in C. Unattractive.
* Let clients cache the output of query-qmp-schema.
It changes only on QEMU upgrades, i.e. rarely. Provide a command
query-qmp-schema-hash. Clients can have a cache indexed by hash,
and re-query the schema only when they don't have it cached. Even
simpler: put the hash in the QMP greeting.
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
2015-09-16 14:06:28 +03:00
|
|
|
|
2015-11-06 09:35:35 +03:00
|
|
|
{ "name": "[str]", "meta-type": "array",
|
qapi: New QMP command query-qmp-schema for QMP introspection
qapi/introspect.json defines the introspection schema. It's designed
for QMP introspection, but should do for similar uses, such as QGA.
The introspection schema does not reflect all the rules and
restrictions that apply to QAPI schemata. A valid QAPI schema has an
introspection value conforming to the introspection schema, but the
converse is not true.
Introspection lowers away a number of schema details, and makes
implicit things explicit:
* The built-in types are declared with their JSON type.
All integer types are mapped to 'int', because how many bits we use
internally is an implementation detail. It could be pressed into
external interface service as very approximate range information,
but that's a bad idea. If we need range information, we better do
it properly.
* Implicit type definitions are made explicit, and given
auto-generated names:
- Array types, named by appending "List" to the name of their
element type, like in generated C.
- The enumeration types implicitly defined by simple union types,
named by appending "Kind" to the name of their simple union type,
like in generated C.
- Types that don't occur in generated C. Their names start with ':'
so they don't clash with the user's names.
* All type references are by name.
* The struct and union types are generalized into an object type.
* Base types are flattened.
* Commands take a single argument and return a single result.
Dictionary argument or list result is an implicit type definition.
The empty object type is used when a command takes no arguments or
produces no results.
The argument is always of object type, but the introspection schema
doesn't reflect that.
The 'gen': false directive is omitted as implementation detail.
The 'success-response' directive is omitted as well for now, even
though it's not an implementation detail, because it's not used by
QMP.
* Events carry a single data value.
Implicit type definition and empty object type use, just like for
commands.
The value is of object type, but the introspection schema doesn't
reflect that.
* Types not used by commands or events are omitted.
Indirect use counts as use.
* Optional members have a default, which can only be null right now
Instead of a mandatory "optional" flag, we have an optional default.
No default means mandatory, default null means optional without
default value. Non-null is available for optional with default
(possible future extension).
* Clients should *not* look up types by name, because type names are
not ABI. Look up the command or event you're interested in, then
follow the references.
TODO Should we hide the type names to eliminate the temptation?
New generator scripts/qapi-introspect.py computes an introspection
value for its input, and generates a C variable holding it.
It can generate awfully long lines. Marked TODO.
A new test-qmp-input-visitor test case feeds its result for both
tests/qapi-schema/qapi-schema-test.json and qapi-schema.json to a
QmpInputVisitor to verify it actually conforms to the schema.
New QMP command query-qmp-schema takes its return value from that
variable. Its reply is some 85KiBytes for me right now.
If this turns out to be too much, we have a couple of options:
* We can use shorter names in the JSON. Not the QMP style.
* Optionally return the sub-schema for commands and events given as
arguments.
Right now qmp_query_schema() sends the string literal computed by
qmp-introspect.py. To compute sub-schema at run time, we'd have to
duplicate parts of qapi-introspect.py in C. Unattractive.
* Let clients cache the output of query-qmp-schema.
It changes only on QEMU upgrades, i.e. rarely. Provide a command
query-qmp-schema-hash. Clients can have a cache indexed by hash,
and re-query the schema only when they don't have it cached. Even
simpler: put the hash in the QMP greeting.
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
2015-09-16 14:06:28 +03:00
|
|
|
"element-type": "str" }
|
|
|
|
|
|
|
|
The SchemaInfo for an enumeration type has meta-type "enum" and
|
qapi: Enable enum member introspection to show more than name
The next commit will add feature flags to enum members. There's a
problem, though: query-qmp-schema shows an enum type's members as an
array of member names (SchemaInfoEnum member @values). If it showed
an array of objects with a name member, we could simply add more
members to these objects. Since it's just strings, we can't.
I can see three ways to correct this design mistake:
1. Do it the way we should have done it, plus compatibility goo.
We want a ['SchemaInfoEnumMember'] member in SchemaInfoEnum. Since
changing @values would be a compatibility break, add a new member
@members instead.
@values is now redundant. In my testing, output of
qemu-system-x86_64's query-qmp-schema grows by 11% (18.5KiB).
We can deprecate @values now and drop it later. This will break
outmoded clients. Well-behaved clients such as libvirt are
expected to break cleanly.
2. Like 1, but omit "boring" elements of @member, and empty @member.
@values does not become redundant. @members augments it. Somewhat
cumbersome, but output of query-qmp-schema grows only as we make
enum members non-boring.
There is nothing to deprecate here.
3. Versioned query-qmp-schema.
query-qmp-schema provides either @values or @members. The QMP
client can select which version it wants. There is no redundant
output.
We can deprecate old versions and eventually drop them. This will
break outmoded clients. Breaking cleanly is easier than for 1.
While 1 and 2 operate within the common rules for compatible
evolution apply (section "Compatibility considerations" in
docs/devel/qapi-code-gen.rst), 3 bypasses them. Attractive when
operating within the rules is just too awkward. Not the case here.
This commit implements 1. Libvirt developers prefer it.
Deprecate @values in favour of @members. Since query-qmp-schema
compatibility is pretty fundamental for management applications, an
extended grace period is advised.
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Tested-by: Peter Krempa <pkrempa@redhat.com>
Acked-by: Peter Krempa <pkrempa@redhat.com>
Message-Id: <20211025042405.3762351-2-armbru@redhat.com>
Reviewed-by: John Snow <jsnow@redhat.com>
2021-10-25 07:24:01 +03:00
|
|
|
variant member "members".
|
|
|
|
|
|
|
|
"members" is a JSON array describing the enumeration values. Each
|
2021-10-25 07:24:02 +03:00
|
|
|
element is a JSON object with member "name" (the member's name), and
|
|
|
|
optionally "features" (a JSON array of feature strings). The
|
qapi: Enable enum member introspection to show more than name
The next commit will add feature flags to enum members. There's a
problem, though: query-qmp-schema shows an enum type's members as an
array of member names (SchemaInfoEnum member @values). If it showed
an array of objects with a name member, we could simply add more
members to these objects. Since it's just strings, we can't.
I can see three ways to correct this design mistake:
1. Do it the way we should have done it, plus compatibility goo.
We want a ['SchemaInfoEnumMember'] member in SchemaInfoEnum. Since
changing @values would be a compatibility break, add a new member
@members instead.
@values is now redundant. In my testing, output of
qemu-system-x86_64's query-qmp-schema grows by 11% (18.5KiB).
We can deprecate @values now and drop it later. This will break
outmoded clients. Well-behaved clients such as libvirt are
expected to break cleanly.
2. Like 1, but omit "boring" elements of @member, and empty @member.
@values does not become redundant. @members augments it. Somewhat
cumbersome, but output of query-qmp-schema grows only as we make
enum members non-boring.
There is nothing to deprecate here.
3. Versioned query-qmp-schema.
query-qmp-schema provides either @values or @members. The QMP
client can select which version it wants. There is no redundant
output.
We can deprecate old versions and eventually drop them. This will
break outmoded clients. Breaking cleanly is easier than for 1.
While 1 and 2 operate within the common rules for compatible
evolution apply (section "Compatibility considerations" in
docs/devel/qapi-code-gen.rst), 3 bypasses them. Attractive when
operating within the rules is just too awkward. Not the case here.
This commit implements 1. Libvirt developers prefer it.
Deprecate @values in favour of @members. Since query-qmp-schema
compatibility is pretty fundamental for management applications, an
extended grace period is advised.
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Tested-by: Peter Krempa <pkrempa@redhat.com>
Acked-by: Peter Krempa <pkrempa@redhat.com>
Message-Id: <20211025042405.3762351-2-armbru@redhat.com>
Reviewed-by: John Snow <jsnow@redhat.com>
2021-10-25 07:24:01 +03:00
|
|
|
"members" array is in no particular order; clients must search the
|
|
|
|
entire array when learning whether a particular value is supported.
|
qapi: New QMP command query-qmp-schema for QMP introspection
qapi/introspect.json defines the introspection schema. It's designed
for QMP introspection, but should do for similar uses, such as QGA.
The introspection schema does not reflect all the rules and
restrictions that apply to QAPI schemata. A valid QAPI schema has an
introspection value conforming to the introspection schema, but the
converse is not true.
Introspection lowers away a number of schema details, and makes
implicit things explicit:
* The built-in types are declared with their JSON type.
All integer types are mapped to 'int', because how many bits we use
internally is an implementation detail. It could be pressed into
external interface service as very approximate range information,
but that's a bad idea. If we need range information, we better do
it properly.
* Implicit type definitions are made explicit, and given
auto-generated names:
- Array types, named by appending "List" to the name of their
element type, like in generated C.
- The enumeration types implicitly defined by simple union types,
named by appending "Kind" to the name of their simple union type,
like in generated C.
- Types that don't occur in generated C. Their names start with ':'
so they don't clash with the user's names.
* All type references are by name.
* The struct and union types are generalized into an object type.
* Base types are flattened.
* Commands take a single argument and return a single result.
Dictionary argument or list result is an implicit type definition.
The empty object type is used when a command takes no arguments or
produces no results.
The argument is always of object type, but the introspection schema
doesn't reflect that.
The 'gen': false directive is omitted as implementation detail.
The 'success-response' directive is omitted as well for now, even
though it's not an implementation detail, because it's not used by
QMP.
* Events carry a single data value.
Implicit type definition and empty object type use, just like for
commands.
The value is of object type, but the introspection schema doesn't
reflect that.
* Types not used by commands or events are omitted.
Indirect use counts as use.
* Optional members have a default, which can only be null right now
Instead of a mandatory "optional" flag, we have an optional default.
No default means mandatory, default null means optional without
default value. Non-null is available for optional with default
(possible future extension).
* Clients should *not* look up types by name, because type names are
not ABI. Look up the command or event you're interested in, then
follow the references.
TODO Should we hide the type names to eliminate the temptation?
New generator scripts/qapi-introspect.py computes an introspection
value for its input, and generates a C variable holding it.
It can generate awfully long lines. Marked TODO.
A new test-qmp-input-visitor test case feeds its result for both
tests/qapi-schema/qapi-schema-test.json and qapi-schema.json to a
QmpInputVisitor to verify it actually conforms to the schema.
New QMP command query-qmp-schema takes its return value from that
variable. Its reply is some 85KiBytes for me right now.
If this turns out to be too much, we have a couple of options:
* We can use shorter names in the JSON. Not the QMP style.
* Optionally return the sub-schema for commands and events given as
arguments.
Right now qmp_query_schema() sends the string literal computed by
qmp-introspect.py. To compute sub-schema at run time, we'd have to
duplicate parts of qapi-introspect.py in C. Unattractive.
* Let clients cache the output of query-qmp-schema.
It changes only on QEMU upgrades, i.e. rarely. Provide a command
query-qmp-schema-hash. Clients can have a cache indexed by hash,
and re-query the schema only when they don't have it cached. Even
simpler: put the hash in the QMP greeting.
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
2015-09-16 14:06:28 +03:00
|
|
|
|
2021-07-21 02:56:19 +03:00
|
|
|
Example: the SchemaInfo for MyEnum from section `Enumeration types`_ ::
|
qapi: New QMP command query-qmp-schema for QMP introspection
qapi/introspect.json defines the introspection schema. It's designed
for QMP introspection, but should do for similar uses, such as QGA.
The introspection schema does not reflect all the rules and
restrictions that apply to QAPI schemata. A valid QAPI schema has an
introspection value conforming to the introspection schema, but the
converse is not true.
Introspection lowers away a number of schema details, and makes
implicit things explicit:
* The built-in types are declared with their JSON type.
All integer types are mapped to 'int', because how many bits we use
internally is an implementation detail. It could be pressed into
external interface service as very approximate range information,
but that's a bad idea. If we need range information, we better do
it properly.
* Implicit type definitions are made explicit, and given
auto-generated names:
- Array types, named by appending "List" to the name of their
element type, like in generated C.
- The enumeration types implicitly defined by simple union types,
named by appending "Kind" to the name of their simple union type,
like in generated C.
- Types that don't occur in generated C. Their names start with ':'
so they don't clash with the user's names.
* All type references are by name.
* The struct and union types are generalized into an object type.
* Base types are flattened.
* Commands take a single argument and return a single result.
Dictionary argument or list result is an implicit type definition.
The empty object type is used when a command takes no arguments or
produces no results.
The argument is always of object type, but the introspection schema
doesn't reflect that.
The 'gen': false directive is omitted as implementation detail.
The 'success-response' directive is omitted as well for now, even
though it's not an implementation detail, because it's not used by
QMP.
* Events carry a single data value.
Implicit type definition and empty object type use, just like for
commands.
The value is of object type, but the introspection schema doesn't
reflect that.
* Types not used by commands or events are omitted.
Indirect use counts as use.
* Optional members have a default, which can only be null right now
Instead of a mandatory "optional" flag, we have an optional default.
No default means mandatory, default null means optional without
default value. Non-null is available for optional with default
(possible future extension).
* Clients should *not* look up types by name, because type names are
not ABI. Look up the command or event you're interested in, then
follow the references.
TODO Should we hide the type names to eliminate the temptation?
New generator scripts/qapi-introspect.py computes an introspection
value for its input, and generates a C variable holding it.
It can generate awfully long lines. Marked TODO.
A new test-qmp-input-visitor test case feeds its result for both
tests/qapi-schema/qapi-schema-test.json and qapi-schema.json to a
QmpInputVisitor to verify it actually conforms to the schema.
New QMP command query-qmp-schema takes its return value from that
variable. Its reply is some 85KiBytes for me right now.
If this turns out to be too much, we have a couple of options:
* We can use shorter names in the JSON. Not the QMP style.
* Optionally return the sub-schema for commands and events given as
arguments.
Right now qmp_query_schema() sends the string literal computed by
qmp-introspect.py. To compute sub-schema at run time, we'd have to
duplicate parts of qapi-introspect.py in C. Unattractive.
* Let clients cache the output of query-qmp-schema.
It changes only on QEMU upgrades, i.e. rarely. Provide a command
query-qmp-schema-hash. Clients can have a cache indexed by hash,
and re-query the schema only when they don't have it cached. Even
simpler: put the hash in the QMP greeting.
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
2015-09-16 14:06:28 +03:00
|
|
|
|
|
|
|
{ "name": "MyEnum", "meta-type": "enum",
|
qapi: Enable enum member introspection to show more than name
The next commit will add feature flags to enum members. There's a
problem, though: query-qmp-schema shows an enum type's members as an
array of member names (SchemaInfoEnum member @values). If it showed
an array of objects with a name member, we could simply add more
members to these objects. Since it's just strings, we can't.
I can see three ways to correct this design mistake:
1. Do it the way we should have done it, plus compatibility goo.
We want a ['SchemaInfoEnumMember'] member in SchemaInfoEnum. Since
changing @values would be a compatibility break, add a new member
@members instead.
@values is now redundant. In my testing, output of
qemu-system-x86_64's query-qmp-schema grows by 11% (18.5KiB).
We can deprecate @values now and drop it later. This will break
outmoded clients. Well-behaved clients such as libvirt are
expected to break cleanly.
2. Like 1, but omit "boring" elements of @member, and empty @member.
@values does not become redundant. @members augments it. Somewhat
cumbersome, but output of query-qmp-schema grows only as we make
enum members non-boring.
There is nothing to deprecate here.
3. Versioned query-qmp-schema.
query-qmp-schema provides either @values or @members. The QMP
client can select which version it wants. There is no redundant
output.
We can deprecate old versions and eventually drop them. This will
break outmoded clients. Breaking cleanly is easier than for 1.
While 1 and 2 operate within the common rules for compatible
evolution apply (section "Compatibility considerations" in
docs/devel/qapi-code-gen.rst), 3 bypasses them. Attractive when
operating within the rules is just too awkward. Not the case here.
This commit implements 1. Libvirt developers prefer it.
Deprecate @values in favour of @members. Since query-qmp-schema
compatibility is pretty fundamental for management applications, an
extended grace period is advised.
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Tested-by: Peter Krempa <pkrempa@redhat.com>
Acked-by: Peter Krempa <pkrempa@redhat.com>
Message-Id: <20211025042405.3762351-2-armbru@redhat.com>
Reviewed-by: John Snow <jsnow@redhat.com>
2021-10-25 07:24:01 +03:00
|
|
|
"members": [
|
|
|
|
{ "name": "value1" },
|
|
|
|
{ "name": "value2" },
|
|
|
|
{ "name": "value3" }
|
|
|
|
] }
|
qapi: New QMP command query-qmp-schema for QMP introspection
qapi/introspect.json defines the introspection schema. It's designed
for QMP introspection, but should do for similar uses, such as QGA.
The introspection schema does not reflect all the rules and
restrictions that apply to QAPI schemata. A valid QAPI schema has an
introspection value conforming to the introspection schema, but the
converse is not true.
Introspection lowers away a number of schema details, and makes
implicit things explicit:
* The built-in types are declared with their JSON type.
All integer types are mapped to 'int', because how many bits we use
internally is an implementation detail. It could be pressed into
external interface service as very approximate range information,
but that's a bad idea. If we need range information, we better do
it properly.
* Implicit type definitions are made explicit, and given
auto-generated names:
- Array types, named by appending "List" to the name of their
element type, like in generated C.
- The enumeration types implicitly defined by simple union types,
named by appending "Kind" to the name of their simple union type,
like in generated C.
- Types that don't occur in generated C. Their names start with ':'
so they don't clash with the user's names.
* All type references are by name.
* The struct and union types are generalized into an object type.
* Base types are flattened.
* Commands take a single argument and return a single result.
Dictionary argument or list result is an implicit type definition.
The empty object type is used when a command takes no arguments or
produces no results.
The argument is always of object type, but the introspection schema
doesn't reflect that.
The 'gen': false directive is omitted as implementation detail.
The 'success-response' directive is omitted as well for now, even
though it's not an implementation detail, because it's not used by
QMP.
* Events carry a single data value.
Implicit type definition and empty object type use, just like for
commands.
The value is of object type, but the introspection schema doesn't
reflect that.
* Types not used by commands or events are omitted.
Indirect use counts as use.
* Optional members have a default, which can only be null right now
Instead of a mandatory "optional" flag, we have an optional default.
No default means mandatory, default null means optional without
default value. Non-null is available for optional with default
(possible future extension).
* Clients should *not* look up types by name, because type names are
not ABI. Look up the command or event you're interested in, then
follow the references.
TODO Should we hide the type names to eliminate the temptation?
New generator scripts/qapi-introspect.py computes an introspection
value for its input, and generates a C variable holding it.
It can generate awfully long lines. Marked TODO.
A new test-qmp-input-visitor test case feeds its result for both
tests/qapi-schema/qapi-schema-test.json and qapi-schema.json to a
QmpInputVisitor to verify it actually conforms to the schema.
New QMP command query-qmp-schema takes its return value from that
variable. Its reply is some 85KiBytes for me right now.
If this turns out to be too much, we have a couple of options:
* We can use shorter names in the JSON. Not the QMP style.
* Optionally return the sub-schema for commands and events given as
arguments.
Right now qmp_query_schema() sends the string literal computed by
qmp-introspect.py. To compute sub-schema at run time, we'd have to
duplicate parts of qapi-introspect.py in C. Unattractive.
* Let clients cache the output of query-qmp-schema.
It changes only on QEMU upgrades, i.e. rarely. Provide a command
query-qmp-schema-hash. Clients can have a cache indexed by hash,
and re-query the schema only when they don't have it cached. Even
simpler: put the hash in the QMP greeting.
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
2015-09-16 14:06:28 +03:00
|
|
|
|
|
|
|
The SchemaInfo for a built-in type has the same name as the type in
|
2021-07-21 02:56:19 +03:00
|
|
|
the QAPI schema (see section `Built-in Types`_), with one exception
|
qapi: New QMP command query-qmp-schema for QMP introspection
qapi/introspect.json defines the introspection schema. It's designed
for QMP introspection, but should do for similar uses, such as QGA.
The introspection schema does not reflect all the rules and
restrictions that apply to QAPI schemata. A valid QAPI schema has an
introspection value conforming to the introspection schema, but the
converse is not true.
Introspection lowers away a number of schema details, and makes
implicit things explicit:
* The built-in types are declared with their JSON type.
All integer types are mapped to 'int', because how many bits we use
internally is an implementation detail. It could be pressed into
external interface service as very approximate range information,
but that's a bad idea. If we need range information, we better do
it properly.
* Implicit type definitions are made explicit, and given
auto-generated names:
- Array types, named by appending "List" to the name of their
element type, like in generated C.
- The enumeration types implicitly defined by simple union types,
named by appending "Kind" to the name of their simple union type,
like in generated C.
- Types that don't occur in generated C. Their names start with ':'
so they don't clash with the user's names.
* All type references are by name.
* The struct and union types are generalized into an object type.
* Base types are flattened.
* Commands take a single argument and return a single result.
Dictionary argument or list result is an implicit type definition.
The empty object type is used when a command takes no arguments or
produces no results.
The argument is always of object type, but the introspection schema
doesn't reflect that.
The 'gen': false directive is omitted as implementation detail.
The 'success-response' directive is omitted as well for now, even
though it's not an implementation detail, because it's not used by
QMP.
* Events carry a single data value.
Implicit type definition and empty object type use, just like for
commands.
The value is of object type, but the introspection schema doesn't
reflect that.
* Types not used by commands or events are omitted.
Indirect use counts as use.
* Optional members have a default, which can only be null right now
Instead of a mandatory "optional" flag, we have an optional default.
No default means mandatory, default null means optional without
default value. Non-null is available for optional with default
(possible future extension).
* Clients should *not* look up types by name, because type names are
not ABI. Look up the command or event you're interested in, then
follow the references.
TODO Should we hide the type names to eliminate the temptation?
New generator scripts/qapi-introspect.py computes an introspection
value for its input, and generates a C variable holding it.
It can generate awfully long lines. Marked TODO.
A new test-qmp-input-visitor test case feeds its result for both
tests/qapi-schema/qapi-schema-test.json and qapi-schema.json to a
QmpInputVisitor to verify it actually conforms to the schema.
New QMP command query-qmp-schema takes its return value from that
variable. Its reply is some 85KiBytes for me right now.
If this turns out to be too much, we have a couple of options:
* We can use shorter names in the JSON. Not the QMP style.
* Optionally return the sub-schema for commands and events given as
arguments.
Right now qmp_query_schema() sends the string literal computed by
qmp-introspect.py. To compute sub-schema at run time, we'd have to
duplicate parts of qapi-introspect.py in C. Unattractive.
* Let clients cache the output of query-qmp-schema.
It changes only on QEMU upgrades, i.e. rarely. Provide a command
query-qmp-schema-hash. Clients can have a cache indexed by hash,
and re-query the schema only when they don't have it cached. Even
simpler: put the hash in the QMP greeting.
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
2015-09-16 14:06:28 +03:00
|
|
|
detailed below. It has variant member "json-type" that shows how
|
|
|
|
values of this type are encoded on the wire.
|
|
|
|
|
2021-07-21 02:56:17 +03:00
|
|
|
Example: the SchemaInfo for str ::
|
qapi: New QMP command query-qmp-schema for QMP introspection
qapi/introspect.json defines the introspection schema. It's designed
for QMP introspection, but should do for similar uses, such as QGA.
The introspection schema does not reflect all the rules and
restrictions that apply to QAPI schemata. A valid QAPI schema has an
introspection value conforming to the introspection schema, but the
converse is not true.
Introspection lowers away a number of schema details, and makes
implicit things explicit:
* The built-in types are declared with their JSON type.
All integer types are mapped to 'int', because how many bits we use
internally is an implementation detail. It could be pressed into
external interface service as very approximate range information,
but that's a bad idea. If we need range information, we better do
it properly.
* Implicit type definitions are made explicit, and given
auto-generated names:
- Array types, named by appending "List" to the name of their
element type, like in generated C.
- The enumeration types implicitly defined by simple union types,
named by appending "Kind" to the name of their simple union type,
like in generated C.
- Types that don't occur in generated C. Their names start with ':'
so they don't clash with the user's names.
* All type references are by name.
* The struct and union types are generalized into an object type.
* Base types are flattened.
* Commands take a single argument and return a single result.
Dictionary argument or list result is an implicit type definition.
The empty object type is used when a command takes no arguments or
produces no results.
The argument is always of object type, but the introspection schema
doesn't reflect that.
The 'gen': false directive is omitted as implementation detail.
The 'success-response' directive is omitted as well for now, even
though it's not an implementation detail, because it's not used by
QMP.
* Events carry a single data value.
Implicit type definition and empty object type use, just like for
commands.
The value is of object type, but the introspection schema doesn't
reflect that.
* Types not used by commands or events are omitted.
Indirect use counts as use.
* Optional members have a default, which can only be null right now
Instead of a mandatory "optional" flag, we have an optional default.
No default means mandatory, default null means optional without
default value. Non-null is available for optional with default
(possible future extension).
* Clients should *not* look up types by name, because type names are
not ABI. Look up the command or event you're interested in, then
follow the references.
TODO Should we hide the type names to eliminate the temptation?
New generator scripts/qapi-introspect.py computes an introspection
value for its input, and generates a C variable holding it.
It can generate awfully long lines. Marked TODO.
A new test-qmp-input-visitor test case feeds its result for both
tests/qapi-schema/qapi-schema-test.json and qapi-schema.json to a
QmpInputVisitor to verify it actually conforms to the schema.
New QMP command query-qmp-schema takes its return value from that
variable. Its reply is some 85KiBytes for me right now.
If this turns out to be too much, we have a couple of options:
* We can use shorter names in the JSON. Not the QMP style.
* Optionally return the sub-schema for commands and events given as
arguments.
Right now qmp_query_schema() sends the string literal computed by
qmp-introspect.py. To compute sub-schema at run time, we'd have to
duplicate parts of qapi-introspect.py in C. Unattractive.
* Let clients cache the output of query-qmp-schema.
It changes only on QEMU upgrades, i.e. rarely. Provide a command
query-qmp-schema-hash. Clients can have a cache indexed by hash,
and re-query the schema only when they don't have it cached. Even
simpler: put the hash in the QMP greeting.
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
2015-09-16 14:06:28 +03:00
|
|
|
|
|
|
|
{ "name": "str", "meta-type": "builtin", "json-type": "string" }
|
|
|
|
|
|
|
|
The QAPI schema supports a number of integer types that only differ in
|
|
|
|
how they map to C. They are identical as far as SchemaInfo is
|
|
|
|
concerned. Therefore, they get all mapped to a single type "int" in
|
|
|
|
SchemaInfo.
|
|
|
|
|
|
|
|
As explained above, type names are not part of the wire ABI. Not even
|
|
|
|
the names of built-in types. Clients should examine member
|
|
|
|
"json-type" instead of hard-coding names of built-in types.
|
|
|
|
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2021-07-21 02:56:17 +03:00
|
|
|
Compatibility considerations
|
|
|
|
============================
|
2019-09-13 23:13:46 +03:00
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|
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|
|
Maintaining backward compatibility at the Client JSON Protocol level
|
|
|
|
while evolving the schema requires some care. This section is about
|
|
|
|
syntactic compatibility, which is necessary, but not sufficient, for
|
|
|
|
actual compatibility.
|
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|
Clients send commands with argument data, and receive command
|
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|
|
responses with return data and events with event data.
|
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Adding opt-in functionality to the send direction is backwards
|
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|
|
compatible: adding commands, optional arguments, enumeration values,
|
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|
|
union and alternate branches; turning an argument type into an
|
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|
|
alternate of that type; making mandatory arguments optional. Clients
|
|
|
|
oblivious of the new functionality continue to work.
|
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Incompatible changes include removing commands, command arguments,
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|
enumeration values, union and alternate branches, adding mandatory
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|
command arguments, and making optional arguments mandatory.
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The specified behavior of an absent optional argument should remain
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|
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the same. With proper documentation, this policy still allows some
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|
|
flexibility; for example, when an optional 'buffer-size' argument is
|
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|
|
specified to default to a sensible buffer size, the actual default
|
|
|
|
value can still be changed. The specified default behavior is not the
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|
|
exact size of the buffer, only that the default size is sensible.
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Adding functionality to the receive direction is generally backwards
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compatible: adding events, adding return and event data members.
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Clients are expected to ignore the ones they don't know.
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Removing "unreachable" stuff like events that can't be triggered
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|
anymore, optional return or event data members that can't be sent
|
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|
anymore, and return or event data member (enumeration) values that
|
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|
can't be sent anymore makes no difference to clients, except for
|
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|
introspection. The latter can conceivably confuse clients, so tread
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|
carefully.
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Incompatible changes include removing return and event data members.
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Any change to a command definition's 'data' or one of the types used
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there (recursively) needs to consider send direction compatibility.
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Any change to a command definition's 'return', an event definition's
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'data', or one of the types used there (recursively) needs to consider
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receive direction compatibility.
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Any change to types used in both contexts need to consider both.
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|
2019-09-13 23:13:48 +03:00
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|
Enumeration type values and complex and alternate type members may be
|
2019-09-13 23:13:46 +03:00
|
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|
reordered freely. For enumerations and alternate types, this doesn't
|
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|
|
affect the wire encoding. For complex types, this might make the
|
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|
|
implementation emit JSON object members in a different order, which
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|
the Client JSON Protocol permits.
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Since type names are not visible in the Client JSON Protocol, types
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may be freely renamed. Even certain refactorings are invisible, such
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as splitting members from one type into a common base type.
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2021-07-21 02:56:17 +03:00
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Code generation
|
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|
===============
|
2011-07-19 23:50:46 +04:00
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|
2018-02-26 22:48:58 +03:00
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The QAPI code generator qapi-gen.py generates code and documentation
|
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|
from the schema. Together with the core QAPI libraries, this code
|
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|
|
provides everything required to take JSON commands read in by a Client
|
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|
JSON Protocol server, unmarshal the arguments into the underlying C
|
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|
|
types, call into the corresponding C function, map the response back
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to a Client JSON Protocol response to be returned to the user, and
|
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|
introspect the commands.
|
2011-07-19 23:50:46 +04:00
|
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|
2016-03-03 19:16:46 +03:00
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As an example, we'll use the following schema, which describes a
|
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single complex user-defined type, along with command which takes a
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|
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list of that type as a parameter, and returns a single element of that
|
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type. The user is responsible for writing the implementation of
|
2021-07-21 02:56:17 +03:00
|
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|
qmp_my_command(); everything else is produced by the generator. ::
|
2011-07-19 23:50:46 +04:00
|
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|
2014-05-14 19:27:23 +04:00
|
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|
$ cat example-schema.json
|
2015-05-04 18:05:26 +03:00
|
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{ 'struct': 'UserDefOne',
|
2022-11-04 19:06:45 +03:00
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'data': { 'integer': 'int', '*string': 'str', '*flag': 'bool' } }
|
2011-07-19 23:50:46 +04:00
|
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{ 'command': 'my-command',
|
2016-03-03 19:16:46 +03:00
|
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'data': { 'arg1': ['UserDefOne'] },
|
2011-07-19 23:50:46 +04:00
|
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|
'returns': 'UserDefOne' }
|
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|
2014-09-26 19:20:33 +04:00
|
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{ 'event': 'MY_EVENT' }
|
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|
2021-07-21 02:56:17 +03:00
|
|
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We run qapi-gen.py like this::
|
2018-02-26 22:48:58 +03:00
|
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$ python scripts/qapi-gen.py --output-dir="qapi-generated" \
|
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|
|
--prefix="example-" example-schema.json
|
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|
2016-03-03 19:16:46 +03:00
|
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|
For a more thorough look at generated code, the testsuite includes
|
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|
|
tests/qapi-schema/qapi-schema-tests.json that covers more examples of
|
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|
|
what the generator will accept, and compiles the resulting C code as
|
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|
|
part of 'make check-unit'.
|
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|
2021-07-21 02:56:17 +03:00
|
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Code generated for QAPI types
|
|
|
|
-----------------------------
|
2011-07-19 23:50:46 +04:00
|
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|
2018-02-26 22:48:58 +03:00
|
|
|
The following files are created:
|
2011-07-19 23:50:46 +04:00
|
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|
|
2021-07-21 02:56:17 +03:00
|
|
|
``$(prefix)qapi-types.h``
|
|
|
|
C types corresponding to types defined in the schema
|
2018-02-26 22:48:58 +03:00
|
|
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|
2021-07-21 02:56:17 +03:00
|
|
|
``$(prefix)qapi-types.c``
|
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|
|
Cleanup functions for the above C types
|
2011-07-19 23:50:46 +04:00
|
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|
The $(prefix) is an optional parameter used as a namespace to keep the
|
|
|
|
generated code from one schema/code-generation separated from others so code
|
|
|
|
can be generated/used from multiple schemas without clobbering previously
|
|
|
|
created code.
|
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|
2021-07-21 02:56:17 +03:00
|
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|
Example::
|
2011-07-19 23:50:46 +04:00
|
|
|
|
2016-03-03 19:16:46 +03:00
|
|
|
$ cat qapi-generated/example-qapi-types.h
|
2021-07-21 02:56:17 +03:00
|
|
|
[Uninteresting stuff omitted...]
|
2016-03-03 19:16:46 +03:00
|
|
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|
|
|
|
#ifndef EXAMPLE_QAPI_TYPES_H
|
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|
|
#define EXAMPLE_QAPI_TYPES_H
|
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|
|
|
2018-08-28 15:07:36 +03:00
|
|
|
#include "qapi/qapi-builtin-types.h"
|
2016-03-03 19:16:46 +03:00
|
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|
|
typedef struct UserDefOne UserDefOne;
|
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typedef struct UserDefOneList UserDefOneList;
|
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|
2017-08-24 11:45:56 +03:00
|
|
|
typedef struct q_obj_my_command_arg q_obj_my_command_arg;
|
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|
|
|
2016-03-03 19:16:46 +03:00
|
|
|
struct UserDefOne {
|
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|
|
int64_t integer;
|
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|
|
char *string;
|
2022-11-04 19:06:45 +03:00
|
|
|
bool has_flag;
|
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|
|
bool flag;
|
2016-03-03 19:16:46 +03:00
|
|
|
};
|
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|
|
void qapi_free_UserDefOne(UserDefOne *obj);
|
qapi: enable use of g_autoptr with QAPI types
Currently QAPI generates a type and function for free'ing it:
typedef struct QCryptoBlockCreateOptions QCryptoBlockCreateOptions;
void qapi_free_QCryptoBlockCreateOptions(QCryptoBlockCreateOptions *obj);
This is used in the traditional manner:
QCryptoBlockCreateOptions *opts = NULL;
opts = g_new0(QCryptoBlockCreateOptions, 1);
....do stuff with opts...
qapi_free_QCryptoBlockCreateOptions(opts);
Since bumping the min glib to 2.48, QEMU has incrementally adopted the
use of g_auto/g_autoptr. This allows the compiler to run a function to
free a variable when it goes out of scope, the benefit being the
compiler can guarantee it is freed in all possible code ptahs.
This benefit is applicable to QAPI types too, and given the seriously
long method names for some qapi_free_XXXX() functions, is much less
typing. This change thus makes the code generator emit:
G_DEFINE_AUTOPTR_CLEANUP_FUNC(QCryptoBlockCreateOptions,
qapi_free_QCryptoBlockCreateOptions)
The above code example now becomes
g_autoptr(QCryptoBlockCreateOptions) opts = NULL;
opts = g_new0(QCryptoBlockCreateOptions, 1);
....do stuff with opts...
Note, if the local pointer needs to live beyond the scope holding the
variable, then g_steal_pointer can be used. This is useful to return the
pointer to the caller in the success codepath, while letting it be freed
in all error codepaths.
return g_steal_pointer(&opts);
The crypto/block.h header needs updating to avoid symbol clash now that
the g_autoptr support is a standard QAPI feature.
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
Message-Id: <20200723153845.2934357-1-berrange@redhat.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>
2020-07-23 18:38:45 +03:00
|
|
|
G_DEFINE_AUTOPTR_CLEANUP_FUNC(UserDefOne, qapi_free_UserDefOne)
|
2016-03-03 19:16:46 +03:00
|
|
|
|
|
|
|
struct UserDefOneList {
|
|
|
|
UserDefOneList *next;
|
|
|
|
UserDefOne *value;
|
|
|
|
};
|
|
|
|
|
|
|
|
void qapi_free_UserDefOneList(UserDefOneList *obj);
|
qapi: enable use of g_autoptr with QAPI types
Currently QAPI generates a type and function for free'ing it:
typedef struct QCryptoBlockCreateOptions QCryptoBlockCreateOptions;
void qapi_free_QCryptoBlockCreateOptions(QCryptoBlockCreateOptions *obj);
This is used in the traditional manner:
QCryptoBlockCreateOptions *opts = NULL;
opts = g_new0(QCryptoBlockCreateOptions, 1);
....do stuff with opts...
qapi_free_QCryptoBlockCreateOptions(opts);
Since bumping the min glib to 2.48, QEMU has incrementally adopted the
use of g_auto/g_autoptr. This allows the compiler to run a function to
free a variable when it goes out of scope, the benefit being the
compiler can guarantee it is freed in all possible code ptahs.
This benefit is applicable to QAPI types too, and given the seriously
long method names for some qapi_free_XXXX() functions, is much less
typing. This change thus makes the code generator emit:
G_DEFINE_AUTOPTR_CLEANUP_FUNC(QCryptoBlockCreateOptions,
qapi_free_QCryptoBlockCreateOptions)
The above code example now becomes
g_autoptr(QCryptoBlockCreateOptions) opts = NULL;
opts = g_new0(QCryptoBlockCreateOptions, 1);
....do stuff with opts...
Note, if the local pointer needs to live beyond the scope holding the
variable, then g_steal_pointer can be used. This is useful to return the
pointer to the caller in the success codepath, while letting it be freed
in all error codepaths.
return g_steal_pointer(&opts);
The crypto/block.h header needs updating to avoid symbol clash now that
the g_autoptr support is a standard QAPI feature.
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
Message-Id: <20200723153845.2934357-1-berrange@redhat.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>
2020-07-23 18:38:45 +03:00
|
|
|
G_DEFINE_AUTOPTR_CLEANUP_FUNC(UserDefOneList, qapi_free_UserDefOneList)
|
2016-03-03 19:16:46 +03:00
|
|
|
|
2017-08-24 11:45:56 +03:00
|
|
|
struct q_obj_my_command_arg {
|
|
|
|
UserDefOneList *arg1;
|
|
|
|
};
|
|
|
|
|
2018-08-28 15:07:36 +03:00
|
|
|
#endif /* EXAMPLE_QAPI_TYPES_H */
|
2014-05-14 19:27:23 +04:00
|
|
|
$ cat qapi-generated/example-qapi-types.c
|
2021-07-21 02:56:17 +03:00
|
|
|
[Uninteresting stuff omitted...]
|
2014-05-07 11:53:43 +04:00
|
|
|
|
qapi-types: Convert to QAPISchemaVisitor, fixing flat unions
Fixes flat unions to get the base's base members. Test case is from
commit 2fc0043, in qapi-schema-test.json:
{ 'union': 'UserDefFlatUnion',
'base': 'UserDefUnionBase',
'discriminator': 'enum1',
'data': { 'value1' : 'UserDefA',
'value2' : 'UserDefB',
'value3' : 'UserDefB' } }
{ 'struct': 'UserDefUnionBase',
'base': 'UserDefZero',
'data': { 'string': 'str', 'enum1': 'EnumOne' } }
{ 'struct': 'UserDefZero',
'data': { 'integer': 'int' } }
Patch's effect on UserDefFlatUnion:
struct UserDefFlatUnion {
/* Members inherited from UserDefUnionBase: */
+ int64_t integer;
char *string;
EnumOne enum1;
/* Own members: */
union { /* union tag is @enum1 */
void *data;
UserDefA *value1;
UserDefB *value2;
UserDefB *value3;
};
};
Flat union visitors remain broken. They'll be fixed next.
Code is generated in a different order now, but that doesn't matter.
The two guards QAPI_TYPES_BUILTIN_STRUCT_DECL and
QAPI_TYPES_BUILTIN_CLEANUP_DECL are replaced by just
QAPI_TYPES_BUILTIN.
Two ugly special cases for simple unions now stand out like sore
thumbs:
1. The type tag is named 'type' everywhere, except in generated C,
where it's 'kind'.
2. QAPISchema lowers simple unions to semantically equivalent flat
unions. However, the C generated for a simple unions differs from
the C generated for its equivalent flat union, and we therefore
need special code to preserve that pointless difference for now.
Mark both TODO.
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Daniel P. Berrange <berrange@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
2015-09-16 14:06:09 +03:00
|
|
|
void qapi_free_UserDefOne(UserDefOne *obj)
|
2014-05-07 11:53:43 +04:00
|
|
|
{
|
|
|
|
Visitor *v;
|
|
|
|
|
|
|
|
if (!obj) {
|
|
|
|
return;
|
|
|
|
}
|
|
|
|
|
qapi: Add new visit_free() function
Making each visitor provide its own (awkwardly-named) FOO_cleanup()
is unusual, when we can instead have a polymorphic visit_free()
interface. Over the next few patches, we can use the polymorphic
functions to eliminate the need for a FOO_get_visitor() function
for accessing specific visitor functionality, once everything can
be accessed directly through the Visitor* interfaces.
The dealloc visitor is the first one converted to completely use
the new entry point, since qapi_dealloc_visitor_cleanup() was the
only reason that qapi_dealloc_get_visitor() existed, and only
generated and testsuite code was even using it. With the new
visit_free() entry point in place, we no longer need to expose
the QapiDeallocVisitor subtype through qapi_dealloc_visitor_new(),
and can get by with less generated code, with diffs that look like:
| void qapi_free_ACPIOSTInfo(ACPIOSTInfo *obj)
| {
|- QapiDeallocVisitor *qdv;
| Visitor *v;
|
| if (!obj) {
| return;
| }
|
|- qdv = qapi_dealloc_visitor_new();
|- v = qapi_dealloc_get_visitor(qdv);
|+ v = qapi_dealloc_visitor_new();
| visit_type_ACPIOSTInfo(v, NULL, &obj, NULL);
|- qapi_dealloc_visitor_cleanup(qdv);
|+ visit_free(v);
|}
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <1465490926-28625-5-git-send-email-eblake@redhat.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>
2016-06-09 19:48:35 +03:00
|
|
|
v = qapi_dealloc_visitor_new();
|
2016-03-03 19:16:46 +03:00
|
|
|
visit_type_UserDefOne(v, NULL, &obj, NULL);
|
qapi: Add new visit_free() function
Making each visitor provide its own (awkwardly-named) FOO_cleanup()
is unusual, when we can instead have a polymorphic visit_free()
interface. Over the next few patches, we can use the polymorphic
functions to eliminate the need for a FOO_get_visitor() function
for accessing specific visitor functionality, once everything can
be accessed directly through the Visitor* interfaces.
The dealloc visitor is the first one converted to completely use
the new entry point, since qapi_dealloc_visitor_cleanup() was the
only reason that qapi_dealloc_get_visitor() existed, and only
generated and testsuite code was even using it. With the new
visit_free() entry point in place, we no longer need to expose
the QapiDeallocVisitor subtype through qapi_dealloc_visitor_new(),
and can get by with less generated code, with diffs that look like:
| void qapi_free_ACPIOSTInfo(ACPIOSTInfo *obj)
| {
|- QapiDeallocVisitor *qdv;
| Visitor *v;
|
| if (!obj) {
| return;
| }
|
|- qdv = qapi_dealloc_visitor_new();
|- v = qapi_dealloc_get_visitor(qdv);
|+ v = qapi_dealloc_visitor_new();
| visit_type_ACPIOSTInfo(v, NULL, &obj, NULL);
|- qapi_dealloc_visitor_cleanup(qdv);
|+ visit_free(v);
|}
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <1465490926-28625-5-git-send-email-eblake@redhat.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>
2016-06-09 19:48:35 +03:00
|
|
|
visit_free(v);
|
2014-05-07 11:53:43 +04:00
|
|
|
}
|
2011-07-19 23:50:46 +04:00
|
|
|
|
qapi-types: Convert to QAPISchemaVisitor, fixing flat unions
Fixes flat unions to get the base's base members. Test case is from
commit 2fc0043, in qapi-schema-test.json:
{ 'union': 'UserDefFlatUnion',
'base': 'UserDefUnionBase',
'discriminator': 'enum1',
'data': { 'value1' : 'UserDefA',
'value2' : 'UserDefB',
'value3' : 'UserDefB' } }
{ 'struct': 'UserDefUnionBase',
'base': 'UserDefZero',
'data': { 'string': 'str', 'enum1': 'EnumOne' } }
{ 'struct': 'UserDefZero',
'data': { 'integer': 'int' } }
Patch's effect on UserDefFlatUnion:
struct UserDefFlatUnion {
/* Members inherited from UserDefUnionBase: */
+ int64_t integer;
char *string;
EnumOne enum1;
/* Own members: */
union { /* union tag is @enum1 */
void *data;
UserDefA *value1;
UserDefB *value2;
UserDefB *value3;
};
};
Flat union visitors remain broken. They'll be fixed next.
Code is generated in a different order now, but that doesn't matter.
The two guards QAPI_TYPES_BUILTIN_STRUCT_DECL and
QAPI_TYPES_BUILTIN_CLEANUP_DECL are replaced by just
QAPI_TYPES_BUILTIN.
Two ugly special cases for simple unions now stand out like sore
thumbs:
1. The type tag is named 'type' everywhere, except in generated C,
where it's 'kind'.
2. QAPISchema lowers simple unions to semantically equivalent flat
unions. However, the C generated for a simple unions differs from
the C generated for its equivalent flat union, and we therefore
need special code to preserve that pointless difference for now.
Mark both TODO.
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Daniel P. Berrange <berrange@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
2015-09-16 14:06:09 +03:00
|
|
|
void qapi_free_UserDefOneList(UserDefOneList *obj)
|
2011-07-19 23:50:46 +04:00
|
|
|
{
|
|
|
|
Visitor *v;
|
|
|
|
|
|
|
|
if (!obj) {
|
|
|
|
return;
|
|
|
|
}
|
|
|
|
|
qapi: Add new visit_free() function
Making each visitor provide its own (awkwardly-named) FOO_cleanup()
is unusual, when we can instead have a polymorphic visit_free()
interface. Over the next few patches, we can use the polymorphic
functions to eliminate the need for a FOO_get_visitor() function
for accessing specific visitor functionality, once everything can
be accessed directly through the Visitor* interfaces.
The dealloc visitor is the first one converted to completely use
the new entry point, since qapi_dealloc_visitor_cleanup() was the
only reason that qapi_dealloc_get_visitor() existed, and only
generated and testsuite code was even using it. With the new
visit_free() entry point in place, we no longer need to expose
the QapiDeallocVisitor subtype through qapi_dealloc_visitor_new(),
and can get by with less generated code, with diffs that look like:
| void qapi_free_ACPIOSTInfo(ACPIOSTInfo *obj)
| {
|- QapiDeallocVisitor *qdv;
| Visitor *v;
|
| if (!obj) {
| return;
| }
|
|- qdv = qapi_dealloc_visitor_new();
|- v = qapi_dealloc_get_visitor(qdv);
|+ v = qapi_dealloc_visitor_new();
| visit_type_ACPIOSTInfo(v, NULL, &obj, NULL);
|- qapi_dealloc_visitor_cleanup(qdv);
|+ visit_free(v);
|}
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <1465490926-28625-5-git-send-email-eblake@redhat.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>
2016-06-09 19:48:35 +03:00
|
|
|
v = qapi_dealloc_visitor_new();
|
2016-03-03 19:16:46 +03:00
|
|
|
visit_type_UserDefOneList(v, NULL, &obj, NULL);
|
qapi: Add new visit_free() function
Making each visitor provide its own (awkwardly-named) FOO_cleanup()
is unusual, when we can instead have a polymorphic visit_free()
interface. Over the next few patches, we can use the polymorphic
functions to eliminate the need for a FOO_get_visitor() function
for accessing specific visitor functionality, once everything can
be accessed directly through the Visitor* interfaces.
The dealloc visitor is the first one converted to completely use
the new entry point, since qapi_dealloc_visitor_cleanup() was the
only reason that qapi_dealloc_get_visitor() existed, and only
generated and testsuite code was even using it. With the new
visit_free() entry point in place, we no longer need to expose
the QapiDeallocVisitor subtype through qapi_dealloc_visitor_new(),
and can get by with less generated code, with diffs that look like:
| void qapi_free_ACPIOSTInfo(ACPIOSTInfo *obj)
| {
|- QapiDeallocVisitor *qdv;
| Visitor *v;
|
| if (!obj) {
| return;
| }
|
|- qdv = qapi_dealloc_visitor_new();
|- v = qapi_dealloc_get_visitor(qdv);
|+ v = qapi_dealloc_visitor_new();
| visit_type_ACPIOSTInfo(v, NULL, &obj, NULL);
|- qapi_dealloc_visitor_cleanup(qdv);
|+ visit_free(v);
|}
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <1465490926-28625-5-git-send-email-eblake@redhat.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>
2016-06-09 19:48:35 +03:00
|
|
|
visit_free(v);
|
2011-07-19 23:50:46 +04:00
|
|
|
}
|
|
|
|
|
2021-07-21 02:56:17 +03:00
|
|
|
[Uninteresting stuff omitted...]
|
2018-08-28 15:07:36 +03:00
|
|
|
|
2021-07-21 02:56:19 +03:00
|
|
|
For a modular QAPI schema (see section `Include directives`_), code for
|
2021-07-21 02:56:17 +03:00
|
|
|
each sub-module SUBDIR/SUBMODULE.json is actually generated into ::
|
2019-02-14 18:22:34 +03:00
|
|
|
|
2021-07-21 02:56:17 +03:00
|
|
|
SUBDIR/$(prefix)qapi-types-SUBMODULE.h
|
|
|
|
SUBDIR/$(prefix)qapi-types-SUBMODULE.c
|
2019-02-14 18:22:34 +03:00
|
|
|
|
|
|
|
If qapi-gen.py is run with option --builtins, additional files are
|
|
|
|
created:
|
|
|
|
|
2021-07-21 02:56:17 +03:00
|
|
|
``qapi-builtin-types.h``
|
|
|
|
C types corresponding to built-in types
|
|
|
|
|
|
|
|
``qapi-builtin-types.c``
|
|
|
|
Cleanup functions for the above C types
|
2019-02-14 18:22:34 +03:00
|
|
|
|
|
|
|
|
2021-07-21 02:56:17 +03:00
|
|
|
Code generated for visiting QAPI types
|
|
|
|
--------------------------------------
|
2011-07-19 23:50:46 +04:00
|
|
|
|
2018-02-26 22:48:58 +03:00
|
|
|
These are the visitor functions used to walk through and convert
|
|
|
|
between a native QAPI C data structure and some other format (such as
|
|
|
|
QObject); the generated functions are named visit_type_FOO() and
|
|
|
|
visit_type_FOO_members().
|
2011-07-19 23:50:46 +04:00
|
|
|
|
|
|
|
The following files are generated:
|
|
|
|
|
2021-07-21 02:56:17 +03:00
|
|
|
``$(prefix)qapi-visit.c``
|
|
|
|
Visitor function for a particular C type, used to automagically
|
|
|
|
convert QObjects into the corresponding C type and vice-versa, as
|
|
|
|
well as for deallocating memory for an existing C type
|
2011-07-19 23:50:46 +04:00
|
|
|
|
2021-07-21 02:56:17 +03:00
|
|
|
``$(prefix)qapi-visit.h``
|
|
|
|
Declarations for previously mentioned visitor functions
|
2011-07-19 23:50:46 +04:00
|
|
|
|
2021-07-21 02:56:17 +03:00
|
|
|
Example::
|
2011-07-19 23:50:46 +04:00
|
|
|
|
2016-03-03 19:16:46 +03:00
|
|
|
$ cat qapi-generated/example-qapi-visit.h
|
2021-07-21 02:56:17 +03:00
|
|
|
[Uninteresting stuff omitted...]
|
2016-03-03 19:16:46 +03:00
|
|
|
|
|
|
|
#ifndef EXAMPLE_QAPI_VISIT_H
|
|
|
|
#define EXAMPLE_QAPI_VISIT_H
|
|
|
|
|
2018-08-28 15:07:36 +03:00
|
|
|
#include "qapi/qapi-builtin-visit.h"
|
|
|
|
#include "example-qapi-types.h"
|
|
|
|
|
2016-03-03 19:16:46 +03:00
|
|
|
|
2020-07-07 19:05:45 +03:00
|
|
|
bool visit_type_UserDefOne_members(Visitor *v, UserDefOne *obj, Error **errp);
|
2021-07-12 18:02:14 +03:00
|
|
|
|
|
|
|
bool visit_type_UserDefOne(Visitor *v, const char *name,
|
|
|
|
UserDefOne **obj, Error **errp);
|
|
|
|
|
|
|
|
bool visit_type_UserDefOneList(Visitor *v, const char *name,
|
|
|
|
UserDefOneList **obj, Error **errp);
|
2016-03-03 19:16:46 +03:00
|
|
|
|
2020-07-07 19:05:45 +03:00
|
|
|
bool visit_type_q_obj_my_command_arg_members(Visitor *v, q_obj_my_command_arg *obj, Error **errp);
|
2017-08-24 11:45:56 +03:00
|
|
|
|
2018-08-28 15:07:36 +03:00
|
|
|
#endif /* EXAMPLE_QAPI_VISIT_H */
|
2014-05-14 19:27:23 +04:00
|
|
|
$ cat qapi-generated/example-qapi-visit.c
|
2021-07-21 02:56:17 +03:00
|
|
|
[Uninteresting stuff omitted...]
|
2011-07-19 23:50:46 +04:00
|
|
|
|
2020-07-07 19:05:45 +03:00
|
|
|
bool visit_type_UserDefOne_members(Visitor *v, UserDefOne *obj, Error **errp)
|
2014-05-07 11:53:43 +04:00
|
|
|
{
|
qapi: Start to elide redundant has_FOO in generated C
In QAPI, absent optional members are distinct from any present value.
We thus represent an optional schema member FOO as two C members: a
FOO with the member's type, and a bool has_FOO. Likewise for function
arguments.
However, has_FOO is actually redundant for a pointer-valued FOO, which
can be null only when has_FOO is false, i.e. has_FOO == !!FOO. Except
for arrays, where we a null FOO can also be a present empty array.
The redundant has_FOO are a nuisance to work with. Improve the
generator to elide them. Uses of has_FOO need to be replaced as
follows.
Tests of has_FOO become the equivalent comparison of FOO with null.
For brevity, this is commonly done by implicit conversion to bool.
Assignments to has_FOO get dropped.
Likewise for arguments to has_FOO parameters.
Beware: code may violate the invariant has_FOO == !!FOO before the
transformation, and get away with it. The above transformation can
then break things. Two cases:
* Absent: if code ignores FOO entirely when !has_FOO (except for
freeing it if necessary), even non-null / uninitialized FOO works.
Such code is known to exist.
* Present: if code ignores FOO entirely when has_FOO, even null FOO
works. Such code should not exist.
In both cases, replacing tests of has_FOO by FOO reverts their sense.
We have to fix the value of FOO then.
To facilitate review of the necessary updates to handwritten code, add
means to opt out of this change, and opt out for all QAPI schema
modules where the change requires updates to handwritten code. The
next few commits will remove these opt-outs in reviewable chunks, then
drop the means to opt out.
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Message-Id: <20221104160712.3005652-5-armbru@redhat.com>
2022-11-04 19:06:46 +03:00
|
|
|
bool has_string = !!obj->string;
|
|
|
|
|
2020-07-07 19:05:45 +03:00
|
|
|
if (!visit_type_int(v, "integer", &obj->integer, errp)) {
|
|
|
|
return false;
|
qapi: Replace uncommon use of the error API by the common one
We commonly use the error API like this:
err = NULL;
foo(..., &err);
if (err) {
goto out;
}
bar(..., &err);
Every error source is checked separately. The second function is only
called when the first one succeeds. Both functions are free to pass
their argument to error_set(). Because error_set() asserts no error
has been set, this effectively means they must not be called with an
error set.
The qapi-generated code uses the error API differently:
// *errp was initialized to NULL somewhere up the call chain
frob(..., errp);
gnat(..., errp);
Errors accumulate in *errp: first error wins, subsequent errors get
dropped. To make this work, the second function does nothing when
called with an error set. Requires non-null errp, or else the second
function can't see the first one fail.
This usage has also bled into visitor tests, and two device model
object property getters rtc_get_date() and balloon_stats_get_all().
With the "accumulate" technique, you need fewer error checks in
callers, and buy that with an error check in every callee. Can be
nice.
However, mixing the two techniques is confusing. You can't use the
"accumulate" technique with functions designed for the "check
separately" technique. You can use the "check separately" technique
with functions designed for the "accumulate" technique, but then
error_set() can't catch you setting an error more than once.
Standardize on the "check separately" technique for now, because it's
overwhelmingly prevalent.
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com>
2014-05-07 11:53:54 +04:00
|
|
|
}
|
qapi: Start to elide redundant has_FOO in generated C
In QAPI, absent optional members are distinct from any present value.
We thus represent an optional schema member FOO as two C members: a
FOO with the member's type, and a bool has_FOO. Likewise for function
arguments.
However, has_FOO is actually redundant for a pointer-valued FOO, which
can be null only when has_FOO is false, i.e. has_FOO == !!FOO. Except
for arrays, where we a null FOO can also be a present empty array.
The redundant has_FOO are a nuisance to work with. Improve the
generator to elide them. Uses of has_FOO need to be replaced as
follows.
Tests of has_FOO become the equivalent comparison of FOO with null.
For brevity, this is commonly done by implicit conversion to bool.
Assignments to has_FOO get dropped.
Likewise for arguments to has_FOO parameters.
Beware: code may violate the invariant has_FOO == !!FOO before the
transformation, and get away with it. The above transformation can
then break things. Two cases:
* Absent: if code ignores FOO entirely when !has_FOO (except for
freeing it if necessary), even non-null / uninitialized FOO works.
Such code is known to exist.
* Present: if code ignores FOO entirely when has_FOO, even null FOO
works. Such code should not exist.
In both cases, replacing tests of has_FOO by FOO reverts their sense.
We have to fix the value of FOO then.
To facilitate review of the necessary updates to handwritten code, add
means to opt out of this change, and opt out for all QAPI schema
modules where the change requires updates to handwritten code. The
next few commits will remove these opt-outs in reviewable chunks, then
drop the means to opt out.
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Message-Id: <20221104160712.3005652-5-armbru@redhat.com>
2022-11-04 19:06:46 +03:00
|
|
|
if (visit_optional(v, "string", &has_string)) {
|
2020-07-07 19:05:45 +03:00
|
|
|
if (!visit_type_str(v, "string", &obj->string, errp)) {
|
|
|
|
return false;
|
2016-03-03 19:16:46 +03:00
|
|
|
}
|
qapi: Replace uncommon use of the error API by the common one
We commonly use the error API like this:
err = NULL;
foo(..., &err);
if (err) {
goto out;
}
bar(..., &err);
Every error source is checked separately. The second function is only
called when the first one succeeds. Both functions are free to pass
their argument to error_set(). Because error_set() asserts no error
has been set, this effectively means they must not be called with an
error set.
The qapi-generated code uses the error API differently:
// *errp was initialized to NULL somewhere up the call chain
frob(..., errp);
gnat(..., errp);
Errors accumulate in *errp: first error wins, subsequent errors get
dropped. To make this work, the second function does nothing when
called with an error set. Requires non-null errp, or else the second
function can't see the first one fail.
This usage has also bled into visitor tests, and two device model
object property getters rtc_get_date() and balloon_stats_get_all().
With the "accumulate" technique, you need fewer error checks in
callers, and buy that with an error check in every callee. Can be
nice.
However, mixing the two techniques is confusing. You can't use the
"accumulate" technique with functions designed for the "check
separately" technique. You can use the "check separately" technique
with functions designed for the "accumulate" technique, but then
error_set() can't catch you setting an error more than once.
Standardize on the "check separately" technique for now, because it's
overwhelmingly prevalent.
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com>
2014-05-07 11:53:54 +04:00
|
|
|
}
|
2022-11-04 19:06:45 +03:00
|
|
|
if (visit_optional(v, "flag", &obj->has_flag)) {
|
|
|
|
if (!visit_type_bool(v, "flag", &obj->flag, errp)) {
|
|
|
|
return false;
|
|
|
|
}
|
|
|
|
}
|
2020-07-07 19:06:08 +03:00
|
|
|
return true;
|
2014-05-07 11:53:43 +04:00
|
|
|
}
|
2011-07-19 23:50:46 +04:00
|
|
|
|
2021-07-12 18:02:14 +03:00
|
|
|
bool visit_type_UserDefOne(Visitor *v, const char *name,
|
|
|
|
UserDefOne **obj, Error **errp)
|
2011-07-19 23:50:46 +04:00
|
|
|
{
|
2020-07-07 19:06:08 +03:00
|
|
|
bool ok = false;
|
qapi: Replace uncommon use of the error API by the common one
We commonly use the error API like this:
err = NULL;
foo(..., &err);
if (err) {
goto out;
}
bar(..., &err);
Every error source is checked separately. The second function is only
called when the first one succeeds. Both functions are free to pass
their argument to error_set(). Because error_set() asserts no error
has been set, this effectively means they must not be called with an
error set.
The qapi-generated code uses the error API differently:
// *errp was initialized to NULL somewhere up the call chain
frob(..., errp);
gnat(..., errp);
Errors accumulate in *errp: first error wins, subsequent errors get
dropped. To make this work, the second function does nothing when
called with an error set. Requires non-null errp, or else the second
function can't see the first one fail.
This usage has also bled into visitor tests, and two device model
object property getters rtc_get_date() and balloon_stats_get_all().
With the "accumulate" technique, you need fewer error checks in
callers, and buy that with an error check in every callee. Can be
nice.
However, mixing the two techniques is confusing. You can't use the
"accumulate" technique with functions designed for the "check
separately" technique. You can use the "check separately" technique
with functions designed for the "accumulate" technique, but then
error_set() can't catch you setting an error more than once.
Standardize on the "check separately" technique for now, because it's
overwhelmingly prevalent.
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com>
2014-05-07 11:53:54 +04:00
|
|
|
|
2020-07-07 19:05:45 +03:00
|
|
|
if (!visit_start_struct(v, name, (void **)obj, sizeof(UserDefOne), errp)) {
|
|
|
|
return false;
|
2016-03-03 19:16:46 +03:00
|
|
|
}
|
|
|
|
if (!*obj) {
|
2020-04-24 11:43:29 +03:00
|
|
|
/* incomplete */
|
|
|
|
assert(visit_is_dealloc(v));
|
2021-07-12 18:02:14 +03:00
|
|
|
ok = true;
|
2016-03-03 19:16:46 +03:00
|
|
|
goto out_obj;
|
2014-05-07 11:53:43 +04:00
|
|
|
}
|
2020-07-07 19:06:08 +03:00
|
|
|
if (!visit_type_UserDefOne_members(v, *obj, errp)) {
|
qapi: Split visit_end_struct() into pieces
As mentioned in previous patches, we want to call visit_end_struct()
functions unconditionally, so that visitors can release resources
tied up since the matching visit_start_struct() without also having
to worry about error priority if more than one error occurs.
Even though error_propagate() can be safely used to ignore a second
error during cleanup caused by a first error, it is simpler if the
cleanup cannot set an error. So, split out the error checking
portion (basically, input visitors checking for unvisited keys) into
a new function visit_check_struct(), which can be safely skipped if
any earlier errors are encountered, and leave the cleanup portion
(which never fails, but must be called unconditionally if
visit_start_struct() succeeded) in visit_end_struct().
Generated code in qapi-visit.c has diffs resembling:
|@@ -59,10 +59,12 @@ void visit_type_ACPIOSTInfo(Visitor *v,
| goto out_obj;
| }
| visit_type_ACPIOSTInfo_members(v, obj, &err);
|- error_propagate(errp, err);
|- err = NULL;
|+ if (err) {
|+ goto out_obj;
|+ }
|+ visit_check_struct(v, &err);
| out_obj:
|- visit_end_struct(v, &err);
|+ visit_end_struct(v);
| out:
and in qapi-event.c:
@@ -47,7 +47,10 @@ void qapi_event_send_acpi_device_ost(ACP
| goto out;
| }
| visit_type_q_obj_ACPI_DEVICE_OST_arg_members(v, ¶m, &err);
|- visit_end_struct(v, err ? NULL : &err);
|+ if (!err) {
|+ visit_check_struct(v, &err);
|+ }
|+ visit_end_struct(v);
| if (err) {
| goto out;
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <1461879932-9020-20-git-send-email-eblake@redhat.com>
[Conflict with a doc fixup resolved]
Signed-off-by: Markus Armbruster <armbru@redhat.com>
2016-04-29 00:45:27 +03:00
|
|
|
goto out_obj;
|
|
|
|
}
|
2020-07-07 19:06:08 +03:00
|
|
|
ok = visit_check_struct(v, errp);
|
2016-03-03 19:16:46 +03:00
|
|
|
out_obj:
|
qapi: Add parameter to visit_end_*
Rather than making the dealloc visitor track of stack of pointers
remembered during visit_start_* in order to free them during
visit_end_*, it's a lot easier to just make all callers pass the
same pointer to visit_end_*. The generated code has access to the
same pointer, while all other users are doing virtual walks and
can pass NULL. The dealloc visitor is then greatly simplified.
All three visit_end_*() functions intentionally take a void**,
even though the visit_start_*() functions differ between void**,
GenericList**, and GenericAlternate**. This is done for several
reasons: when doing a virtual walk, passing NULL doesn't care
what the type is, but when doing a generated walk, we already
have to cast the caller's specific FOO* to call visit_start,
while using void** lets us use visit_end without a cast. Also,
an upcoming patch will add a clone visitor that wants to use
the same implementation for all three visit_end callbacks,
which is made easier if all three share the same signature.
For visitors with already track per-object state (the QMP visitors
via a stack, and the string visitors which do not allow nesting),
add an assertion that the caller is indeed passing the same
pointer to paired calls.
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <1465490926-28625-4-git-send-email-eblake@redhat.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>
2016-06-09 19:48:34 +03:00
|
|
|
visit_end_struct(v, (void **)obj);
|
2020-07-07 19:06:08 +03:00
|
|
|
if (!ok && visit_is_input(v)) {
|
2016-04-29 00:45:32 +03:00
|
|
|
qapi_free_UserDefOne(*obj);
|
|
|
|
*obj = NULL;
|
|
|
|
}
|
2020-07-07 19:06:08 +03:00
|
|
|
return ok;
|
2011-07-19 23:50:46 +04:00
|
|
|
}
|
|
|
|
|
2021-07-12 18:02:14 +03:00
|
|
|
bool visit_type_UserDefOneList(Visitor *v, const char *name,
|
|
|
|
UserDefOneList **obj, Error **errp)
|
2011-07-19 23:50:46 +04:00
|
|
|
{
|
2020-07-07 19:06:08 +03:00
|
|
|
bool ok = false;
|
qapi: Simplify semantics of visit_next_list()
The semantics of the list visit are somewhat baroque, with the
following pseudocode when FooList is used:
start()
for (prev = head; cur = next(prev); prev = &cur) {
visit(&cur->value)
}
Note that these semantics (advance before visit) requires that
the first call to next() return the list head, while all other
calls return the next element of the list; that is, every visitor
implementation is required to track extra state to decide whether
to return the input as-is, or to advance. It also requires an
argument of 'GenericList **' to next(), solely because the first
iteration might need to modify the caller's GenericList head, so
that all other calls have to do a layer of dereferencing.
Thankfully, we only have two uses of list visits in the entire
code base: one in spapr_drc (which completely avoids
visit_next_list(), feeding in integers from a different source
than uint8List), and one in qapi-visit.py. That is, all other
list visitors are generated in qapi-visit.c, and share the same
paradigm based on a qapi FooList type, so we can refactor how
lists are laid out with minimal churn among clients.
We can greatly simplify things by hoisting the special case
into the start() routine, and flipping the order in the loop
to visit before advance:
start(head)
for (tail = *head; tail; tail = next(tail)) {
visit(&tail->value)
}
With the simpler semantics, visitors have less state to track,
the argument to next() is reduced to 'GenericList *', and it
also becomes obvious whether an input visitor is allocating a
FooList during visit_start_list() (rather than the old way of
not knowing if an allocation happened until the first
visit_next_list()). As a minor drawback, we now allocate in
two functions instead of one, and have to pass the size to
both functions (unless we were to tweak the input visitors to
cache the size to start_list for reuse during next_list, but
that defeats the goal of less visitor state).
The signature of visit_start_list() is chosen to match
visit_start_struct(), with the new parameters after 'name'.
The spapr_drc case is a virtual visit, done by passing NULL for
list, similarly to how NULL is passed to visit_start_struct()
when a qapi type is not used in those visits. It was easy to
provide these semantics for qmp-output and dealloc visitors,
and a bit harder for qmp-input (several prerequisite patches
refactored things to make this patch straightforward). But it
turned out that the string and opts visitors munge enough other
state during visit_next_list() to make it easier to just
document and require a GenericList visit for now; an assertion
will remind us to adjust things if we need the semantics in the
future.
Several pre-requisite cleanup patches made the reshuffling of
the various visitors easier; particularly the qmp input visitor.
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <1461879932-9020-24-git-send-email-eblake@redhat.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>
2016-04-29 00:45:31 +03:00
|
|
|
UserDefOneList *tail;
|
|
|
|
size_t size = sizeof(**obj);
|
2014-05-07 11:53:43 +04:00
|
|
|
|
2020-07-07 19:05:45 +03:00
|
|
|
if (!visit_start_list(v, name, (GenericList **)obj, size, errp)) {
|
|
|
|
return false;
|
qapi: Replace uncommon use of the error API by the common one
We commonly use the error API like this:
err = NULL;
foo(..., &err);
if (err) {
goto out;
}
bar(..., &err);
Every error source is checked separately. The second function is only
called when the first one succeeds. Both functions are free to pass
their argument to error_set(). Because error_set() asserts no error
has been set, this effectively means they must not be called with an
error set.
The qapi-generated code uses the error API differently:
// *errp was initialized to NULL somewhere up the call chain
frob(..., errp);
gnat(..., errp);
Errors accumulate in *errp: first error wins, subsequent errors get
dropped. To make this work, the second function does nothing when
called with an error set. Requires non-null errp, or else the second
function can't see the first one fail.
This usage has also bled into visitor tests, and two device model
object property getters rtc_get_date() and balloon_stats_get_all().
With the "accumulate" technique, you need fewer error checks in
callers, and buy that with an error check in every callee. Can be
nice.
However, mixing the two techniques is confusing. You can't use the
"accumulate" technique with functions designed for the "check
separately" technique. You can use the "check separately" technique
with functions designed for the "accumulate" technique, but then
error_set() can't catch you setting an error more than once.
Standardize on the "check separately" technique for now, because it's
overwhelmingly prevalent.
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com>
2014-05-07 11:53:54 +04:00
|
|
|
}
|
|
|
|
|
qapi: Simplify semantics of visit_next_list()
The semantics of the list visit are somewhat baroque, with the
following pseudocode when FooList is used:
start()
for (prev = head; cur = next(prev); prev = &cur) {
visit(&cur->value)
}
Note that these semantics (advance before visit) requires that
the first call to next() return the list head, while all other
calls return the next element of the list; that is, every visitor
implementation is required to track extra state to decide whether
to return the input as-is, or to advance. It also requires an
argument of 'GenericList **' to next(), solely because the first
iteration might need to modify the caller's GenericList head, so
that all other calls have to do a layer of dereferencing.
Thankfully, we only have two uses of list visits in the entire
code base: one in spapr_drc (which completely avoids
visit_next_list(), feeding in integers from a different source
than uint8List), and one in qapi-visit.py. That is, all other
list visitors are generated in qapi-visit.c, and share the same
paradigm based on a qapi FooList type, so we can refactor how
lists are laid out with minimal churn among clients.
We can greatly simplify things by hoisting the special case
into the start() routine, and flipping the order in the loop
to visit before advance:
start(head)
for (tail = *head; tail; tail = next(tail)) {
visit(&tail->value)
}
With the simpler semantics, visitors have less state to track,
the argument to next() is reduced to 'GenericList *', and it
also becomes obvious whether an input visitor is allocating a
FooList during visit_start_list() (rather than the old way of
not knowing if an allocation happened until the first
visit_next_list()). As a minor drawback, we now allocate in
two functions instead of one, and have to pass the size to
both functions (unless we were to tweak the input visitors to
cache the size to start_list for reuse during next_list, but
that defeats the goal of less visitor state).
The signature of visit_start_list() is chosen to match
visit_start_struct(), with the new parameters after 'name'.
The spapr_drc case is a virtual visit, done by passing NULL for
list, similarly to how NULL is passed to visit_start_struct()
when a qapi type is not used in those visits. It was easy to
provide these semantics for qmp-output and dealloc visitors,
and a bit harder for qmp-input (several prerequisite patches
refactored things to make this patch straightforward). But it
turned out that the string and opts visitors munge enough other
state during visit_next_list() to make it easier to just
document and require a GenericList visit for now; an assertion
will remind us to adjust things if we need the semantics in the
future.
Several pre-requisite cleanup patches made the reshuffling of
the various visitors easier; particularly the qmp input visitor.
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <1461879932-9020-24-git-send-email-eblake@redhat.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>
2016-04-29 00:45:31 +03:00
|
|
|
for (tail = *obj; tail;
|
|
|
|
tail = (UserDefOneList *)visit_next_list(v, (GenericList *)tail, size)) {
|
2020-07-07 19:06:08 +03:00
|
|
|
if (!visit_type_UserDefOne(v, NULL, &tail->value, errp)) {
|
|
|
|
goto out_obj;
|
qapi: Simplify semantics of visit_next_list()
The semantics of the list visit are somewhat baroque, with the
following pseudocode when FooList is used:
start()
for (prev = head; cur = next(prev); prev = &cur) {
visit(&cur->value)
}
Note that these semantics (advance before visit) requires that
the first call to next() return the list head, while all other
calls return the next element of the list; that is, every visitor
implementation is required to track extra state to decide whether
to return the input as-is, or to advance. It also requires an
argument of 'GenericList **' to next(), solely because the first
iteration might need to modify the caller's GenericList head, so
that all other calls have to do a layer of dereferencing.
Thankfully, we only have two uses of list visits in the entire
code base: one in spapr_drc (which completely avoids
visit_next_list(), feeding in integers from a different source
than uint8List), and one in qapi-visit.py. That is, all other
list visitors are generated in qapi-visit.c, and share the same
paradigm based on a qapi FooList type, so we can refactor how
lists are laid out with minimal churn among clients.
We can greatly simplify things by hoisting the special case
into the start() routine, and flipping the order in the loop
to visit before advance:
start(head)
for (tail = *head; tail; tail = next(tail)) {
visit(&tail->value)
}
With the simpler semantics, visitors have less state to track,
the argument to next() is reduced to 'GenericList *', and it
also becomes obvious whether an input visitor is allocating a
FooList during visit_start_list() (rather than the old way of
not knowing if an allocation happened until the first
visit_next_list()). As a minor drawback, we now allocate in
two functions instead of one, and have to pass the size to
both functions (unless we were to tweak the input visitors to
cache the size to start_list for reuse during next_list, but
that defeats the goal of less visitor state).
The signature of visit_start_list() is chosen to match
visit_start_struct(), with the new parameters after 'name'.
The spapr_drc case is a virtual visit, done by passing NULL for
list, similarly to how NULL is passed to visit_start_struct()
when a qapi type is not used in those visits. It was easy to
provide these semantics for qmp-output and dealloc visitors,
and a bit harder for qmp-input (several prerequisite patches
refactored things to make this patch straightforward). But it
turned out that the string and opts visitors munge enough other
state during visit_next_list() to make it easier to just
document and require a GenericList visit for now; an assertion
will remind us to adjust things if we need the semantics in the
future.
Several pre-requisite cleanup patches made the reshuffling of
the various visitors easier; particularly the qmp input visitor.
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <1461879932-9020-24-git-send-email-eblake@redhat.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>
2016-04-29 00:45:31 +03:00
|
|
|
}
|
2011-07-19 23:50:46 +04:00
|
|
|
}
|
qapi: Replace uncommon use of the error API by the common one
We commonly use the error API like this:
err = NULL;
foo(..., &err);
if (err) {
goto out;
}
bar(..., &err);
Every error source is checked separately. The second function is only
called when the first one succeeds. Both functions are free to pass
their argument to error_set(). Because error_set() asserts no error
has been set, this effectively means they must not be called with an
error set.
The qapi-generated code uses the error API differently:
// *errp was initialized to NULL somewhere up the call chain
frob(..., errp);
gnat(..., errp);
Errors accumulate in *errp: first error wins, subsequent errors get
dropped. To make this work, the second function does nothing when
called with an error set. Requires non-null errp, or else the second
function can't see the first one fail.
This usage has also bled into visitor tests, and two device model
object property getters rtc_get_date() and balloon_stats_get_all().
With the "accumulate" technique, you need fewer error checks in
callers, and buy that with an error check in every callee. Can be
nice.
However, mixing the two techniques is confusing. You can't use the
"accumulate" technique with functions designed for the "check
separately" technique. You can use the "check separately" technique
with functions designed for the "accumulate" technique, but then
error_set() can't catch you setting an error more than once.
Standardize on the "check separately" technique for now, because it's
overwhelmingly prevalent.
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com>
2014-05-07 11:53:54 +04:00
|
|
|
|
2020-07-07 19:06:08 +03:00
|
|
|
ok = visit_check_list(v, errp);
|
|
|
|
out_obj:
|
qapi: Add parameter to visit_end_*
Rather than making the dealloc visitor track of stack of pointers
remembered during visit_start_* in order to free them during
visit_end_*, it's a lot easier to just make all callers pass the
same pointer to visit_end_*. The generated code has access to the
same pointer, while all other users are doing virtual walks and
can pass NULL. The dealloc visitor is then greatly simplified.
All three visit_end_*() functions intentionally take a void**,
even though the visit_start_*() functions differ between void**,
GenericList**, and GenericAlternate**. This is done for several
reasons: when doing a virtual walk, passing NULL doesn't care
what the type is, but when doing a generated walk, we already
have to cast the caller's specific FOO* to call visit_start,
while using void** lets us use visit_end without a cast. Also,
an upcoming patch will add a clone visitor that wants to use
the same implementation for all three visit_end callbacks,
which is made easier if all three share the same signature.
For visitors with already track per-object state (the QMP visitors
via a stack, and the string visitors which do not allow nesting),
add an assertion that the caller is indeed passing the same
pointer to paired calls.
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <1465490926-28625-4-git-send-email-eblake@redhat.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>
2016-06-09 19:48:34 +03:00
|
|
|
visit_end_list(v, (void **)obj);
|
2020-07-07 19:06:08 +03:00
|
|
|
if (!ok && visit_is_input(v)) {
|
2016-04-29 00:45:32 +03:00
|
|
|
qapi_free_UserDefOneList(*obj);
|
|
|
|
*obj = NULL;
|
|
|
|
}
|
2020-07-07 19:06:08 +03:00
|
|
|
return ok;
|
2011-07-19 23:50:46 +04:00
|
|
|
}
|
|
|
|
|
2020-07-07 19:05:45 +03:00
|
|
|
bool visit_type_q_obj_my_command_arg_members(Visitor *v, q_obj_my_command_arg *obj, Error **errp)
|
2017-08-24 11:45:56 +03:00
|
|
|
{
|
2020-07-07 19:05:45 +03:00
|
|
|
if (!visit_type_UserDefOneList(v, "arg1", &obj->arg1, errp)) {
|
|
|
|
return false;
|
2017-08-24 11:45:56 +03:00
|
|
|
}
|
2020-07-07 19:06:08 +03:00
|
|
|
return true;
|
2017-08-24 11:45:56 +03:00
|
|
|
}
|
|
|
|
|
2021-07-21 02:56:17 +03:00
|
|
|
[Uninteresting stuff omitted...]
|
2018-08-28 15:07:36 +03:00
|
|
|
|
2021-07-21 02:56:19 +03:00
|
|
|
For a modular QAPI schema (see section `Include directives`_), code for
|
2021-07-21 02:56:17 +03:00
|
|
|
each sub-module SUBDIR/SUBMODULE.json is actually generated into ::
|
2019-02-14 18:22:34 +03:00
|
|
|
|
2021-07-21 02:56:17 +03:00
|
|
|
SUBDIR/$(prefix)qapi-visit-SUBMODULE.h
|
|
|
|
SUBDIR/$(prefix)qapi-visit-SUBMODULE.c
|
2019-02-14 18:22:34 +03:00
|
|
|
|
|
|
|
If qapi-gen.py is run with option --builtins, additional files are
|
|
|
|
created:
|
|
|
|
|
2021-07-21 02:56:17 +03:00
|
|
|
``qapi-builtin-visit.h``
|
|
|
|
Visitor functions for built-in types
|
|
|
|
|
|
|
|
``qapi-builtin-visit.c``
|
|
|
|
Declarations for these visitor functions
|
2019-02-14 18:22:34 +03:00
|
|
|
|
|
|
|
|
2021-07-21 02:56:17 +03:00
|
|
|
Code generated for commands
|
|
|
|
---------------------------
|
2018-02-26 22:48:58 +03:00
|
|
|
|
|
|
|
These are the marshaling/dispatch functions for the commands defined
|
|
|
|
in the schema. The generated code provides qmp_marshal_COMMAND(), and
|
|
|
|
declares qmp_COMMAND() that the user must implement.
|
2011-07-19 23:50:46 +04:00
|
|
|
|
2018-02-26 22:48:58 +03:00
|
|
|
The following files are generated:
|
2011-07-19 23:50:46 +04:00
|
|
|
|
2021-07-21 02:56:17 +03:00
|
|
|
``$(prefix)qapi-commands.c``
|
|
|
|
Command marshal/dispatch functions for each QMP command defined in
|
|
|
|
the schema
|
2011-07-19 23:50:46 +04:00
|
|
|
|
2021-07-21 02:56:17 +03:00
|
|
|
``$(prefix)qapi-commands.h``
|
|
|
|
Function prototypes for the QMP commands specified in the schema
|
2011-07-19 23:50:46 +04:00
|
|
|
|
2022-01-26 19:11:28 +03:00
|
|
|
``$(prefix)qapi-commands.trace-events``
|
|
|
|
Trace event declarations, see :ref:`tracing`.
|
|
|
|
|
2021-07-21 02:56:17 +03:00
|
|
|
``$(prefix)qapi-init-commands.h``
|
|
|
|
Command initialization prototype
|
2019-11-20 21:25:48 +03:00
|
|
|
|
2021-07-21 02:56:17 +03:00
|
|
|
``$(prefix)qapi-init-commands.c``
|
|
|
|
Command initialization code
|
2019-11-20 21:25:48 +03:00
|
|
|
|
2021-07-21 02:56:17 +03:00
|
|
|
Example::
|
2011-07-19 23:50:46 +04:00
|
|
|
|
2018-02-11 12:36:05 +03:00
|
|
|
$ cat qapi-generated/example-qapi-commands.h
|
2021-07-21 02:56:17 +03:00
|
|
|
[Uninteresting stuff omitted...]
|
2016-03-03 19:16:46 +03:00
|
|
|
|
2018-08-28 15:07:36 +03:00
|
|
|
#ifndef EXAMPLE_QAPI_COMMANDS_H
|
|
|
|
#define EXAMPLE_QAPI_COMMANDS_H
|
2016-03-03 19:16:46 +03:00
|
|
|
|
|
|
|
#include "example-qapi-types.h"
|
|
|
|
|
|
|
|
UserDefOne *qmp_my_command(UserDefOneList *arg1, Error **errp);
|
2017-08-24 11:45:56 +03:00
|
|
|
void qmp_marshal_my_command(QDict *args, QObject **ret, Error **errp);
|
2016-03-03 19:16:46 +03:00
|
|
|
|
2018-08-28 15:07:36 +03:00
|
|
|
#endif /* EXAMPLE_QAPI_COMMANDS_H */
|
2022-01-26 19:11:28 +03:00
|
|
|
|
|
|
|
$ cat qapi-generated/example-qapi-commands.trace-events
|
|
|
|
# AUTOMATICALLY GENERATED, DO NOT MODIFY
|
|
|
|
|
|
|
|
qmp_enter_my_command(const char *json) "%s"
|
|
|
|
qmp_exit_my_command(const char *result, bool succeeded) "%s %d"
|
|
|
|
|
2018-02-11 12:36:05 +03:00
|
|
|
$ cat qapi-generated/example-qapi-commands.c
|
2021-07-21 02:56:17 +03:00
|
|
|
[Uninteresting stuff omitted...]
|
2011-07-19 23:50:46 +04:00
|
|
|
|
2021-07-12 18:02:14 +03:00
|
|
|
static void qmp_marshal_output_UserDefOne(UserDefOne *ret_in,
|
|
|
|
QObject **ret_out, Error **errp)
|
2011-07-19 23:50:46 +04:00
|
|
|
{
|
|
|
|
Visitor *v;
|
|
|
|
|
2021-07-12 18:02:14 +03:00
|
|
|
v = qobject_output_visitor_new_qmp(ret_out);
|
2020-07-07 19:06:08 +03:00
|
|
|
if (visit_type_UserDefOne(v, "unused", &ret_in, errp)) {
|
qapi: Add new visit_complete() function
Making each output visitor provide its own output collection
function was the only remaining reason for exposing visitor
sub-types to the rest of the code base. Add a polymorphic
visit_complete() function which is a no-op for input visitors,
and which populates an opaque pointer for output visitors. For
maximum type-safety, also add a parameter to the output visitor
constructors with a type-correct version of the output pointer,
and assert that the two uses match.
This approach was considered superior to either passing the
output parameter only during construction (action at a distance
during visit_free() feels awkward) or only during visit_complete()
(defeating type safety makes it easier to use incorrectly).
Most callers were function-local, and therefore a mechanical
conversion; the testsuite was a bit trickier, but the previous
cleanup patch minimized the churn here.
The visit_complete() function may be called at most once; doing
so lets us use transfer semantics rather than duplication or
ref-count semantics to get the just-built output back to the
caller, even though it means our behavior is not idempotent.
Generated code is simplified as follows for events:
|@@ -26,7 +26,7 @@ void qapi_event_send_acpi_device_ost(ACP
| QDict *qmp;
| Error *err = NULL;
| QMPEventFuncEmit emit;
|- QmpOutputVisitor *qov;
|+ QObject *obj;
| Visitor *v;
| q_obj_ACPI_DEVICE_OST_arg param = {
| info
|@@ -39,8 +39,7 @@ void qapi_event_send_acpi_device_ost(ACP
|
| qmp = qmp_event_build_dict("ACPI_DEVICE_OST");
|
|- qov = qmp_output_visitor_new();
|- v = qmp_output_get_visitor(qov);
|+ v = qmp_output_visitor_new(&obj);
|
| visit_start_struct(v, "ACPI_DEVICE_OST", NULL, 0, &err);
| if (err) {
|@@ -55,7 +54,8 @@ void qapi_event_send_acpi_device_ost(ACP
| goto out;
| }
|
|- qdict_put_obj(qmp, "data", qmp_output_get_qobject(qov));
|+ visit_complete(v, &obj);
|+ qdict_put_obj(qmp, "data", obj);
| emit(QAPI_EVENT_ACPI_DEVICE_OST, qmp, &err);
and for commands:
| {
| Error *err = NULL;
|- QmpOutputVisitor *qov = qmp_output_visitor_new();
| Visitor *v;
|
|- v = qmp_output_get_visitor(qov);
|+ v = qmp_output_visitor_new(ret_out);
| visit_type_AddfdInfo(v, "unused", &ret_in, &err);
|- if (err) {
|- goto out;
|+ if (!err) {
|+ visit_complete(v, ret_out);
| }
|- *ret_out = qmp_output_get_qobject(qov);
|-
|-out:
| error_propagate(errp, err);
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <1465490926-28625-13-git-send-email-eblake@redhat.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>
2016-06-09 19:48:43 +03:00
|
|
|
visit_complete(v, ret_out);
|
2014-05-07 11:53:43 +04:00
|
|
|
}
|
qapi: Add new visit_free() function
Making each visitor provide its own (awkwardly-named) FOO_cleanup()
is unusual, when we can instead have a polymorphic visit_free()
interface. Over the next few patches, we can use the polymorphic
functions to eliminate the need for a FOO_get_visitor() function
for accessing specific visitor functionality, once everything can
be accessed directly through the Visitor* interfaces.
The dealloc visitor is the first one converted to completely use
the new entry point, since qapi_dealloc_visitor_cleanup() was the
only reason that qapi_dealloc_get_visitor() existed, and only
generated and testsuite code was even using it. With the new
visit_free() entry point in place, we no longer need to expose
the QapiDeallocVisitor subtype through qapi_dealloc_visitor_new(),
and can get by with less generated code, with diffs that look like:
| void qapi_free_ACPIOSTInfo(ACPIOSTInfo *obj)
| {
|- QapiDeallocVisitor *qdv;
| Visitor *v;
|
| if (!obj) {
| return;
| }
|
|- qdv = qapi_dealloc_visitor_new();
|- v = qapi_dealloc_get_visitor(qdv);
|+ v = qapi_dealloc_visitor_new();
| visit_type_ACPIOSTInfo(v, NULL, &obj, NULL);
|- qapi_dealloc_visitor_cleanup(qdv);
|+ visit_free(v);
|}
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <1465490926-28625-5-git-send-email-eblake@redhat.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>
2016-06-09 19:48:35 +03:00
|
|
|
visit_free(v);
|
|
|
|
v = qapi_dealloc_visitor_new();
|
2016-03-03 19:16:46 +03:00
|
|
|
visit_type_UserDefOne(v, "unused", &ret_in, NULL);
|
qapi: Add new visit_free() function
Making each visitor provide its own (awkwardly-named) FOO_cleanup()
is unusual, when we can instead have a polymorphic visit_free()
interface. Over the next few patches, we can use the polymorphic
functions to eliminate the need for a FOO_get_visitor() function
for accessing specific visitor functionality, once everything can
be accessed directly through the Visitor* interfaces.
The dealloc visitor is the first one converted to completely use
the new entry point, since qapi_dealloc_visitor_cleanup() was the
only reason that qapi_dealloc_get_visitor() existed, and only
generated and testsuite code was even using it. With the new
visit_free() entry point in place, we no longer need to expose
the QapiDeallocVisitor subtype through qapi_dealloc_visitor_new(),
and can get by with less generated code, with diffs that look like:
| void qapi_free_ACPIOSTInfo(ACPIOSTInfo *obj)
| {
|- QapiDeallocVisitor *qdv;
| Visitor *v;
|
| if (!obj) {
| return;
| }
|
|- qdv = qapi_dealloc_visitor_new();
|- v = qapi_dealloc_get_visitor(qdv);
|+ v = qapi_dealloc_visitor_new();
| visit_type_ACPIOSTInfo(v, NULL, &obj, NULL);
|- qapi_dealloc_visitor_cleanup(qdv);
|+ visit_free(v);
|}
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <1465490926-28625-5-git-send-email-eblake@redhat.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>
2016-06-09 19:48:35 +03:00
|
|
|
visit_free(v);
|
2011-07-19 23:50:46 +04:00
|
|
|
}
|
|
|
|
|
2017-08-24 11:45:56 +03:00
|
|
|
void qmp_marshal_my_command(QDict *args, QObject **ret, Error **errp)
|
2011-07-19 23:50:46 +04:00
|
|
|
{
|
2015-09-30 01:21:08 +03:00
|
|
|
Error *err = NULL;
|
2020-07-07 19:06:08 +03:00
|
|
|
bool ok = false;
|
2011-07-19 23:50:46 +04:00
|
|
|
Visitor *v;
|
2020-04-24 11:43:37 +03:00
|
|
|
UserDefOne *retval;
|
2017-08-24 11:45:56 +03:00
|
|
|
q_obj_my_command_arg arg = {0};
|
2011-07-19 23:50:46 +04:00
|
|
|
|
2021-07-12 18:02:14 +03:00
|
|
|
v = qobject_input_visitor_new_qmp(QOBJECT(args));
|
2020-07-07 19:06:08 +03:00
|
|
|
if (!visit_start_struct(v, NULL, NULL, 0, errp)) {
|
qapi-commands: Wrap argument visit in visit_start_struct
The qmp-input visitor was allowing callers to play rather fast
and loose: when visiting a QDict, you could grab members of the
root dictionary without first pushing into the dict; among the
culprit callers was the generated marshal code on the 'arguments'
dictionary of a QMP command. But we are about to tighten the
input visitor, at which point the generated marshal code MUST
follow the same paradigms as everyone else, of pushing into the
struct before grabbing its keys.
Generated code grows as follows:
|@@ -515,7 +641,12 @@ void qmp_marshal_blockdev_backup(QDict *
| BlockdevBackup arg = {0};
|
| v = qmp_input_get_visitor(qiv);
|+ visit_start_struct(v, NULL, NULL, 0, &err);
|+ if (err) {
|+ goto out;
|+ }
| visit_type_BlockdevBackup_members(v, &arg, &err);
|+ visit_end_struct(v, err ? NULL : &err);
| if (err) {
| goto out;
| }
|@@ -527,7 +715,9 @@ out:
| qmp_input_visitor_cleanup(qiv);
| qdv = qapi_dealloc_visitor_new();
| v = qapi_dealloc_get_visitor(qdv);
|+ visit_start_struct(v, NULL, NULL, 0, NULL);
| visit_type_BlockdevBackup_members(v, &arg, NULL);
|+ visit_end_struct(v, NULL);
| qapi_dealloc_visitor_cleanup(qdv);
| }
The use of 'err ? NULL : &err' is temporary; a later patch will
clean that up when it splits visit_end_struct().
Prior to this patch, the fact that there was no final
visit_end_struct() meant that even though we are using a strict
input visit, the marshalling code was not detecting excess input
at the top level (only in nested levels). Fortunately, we have
code in monitor.c:qmp_check_client_args() that also checks for
no excess arguments at the top level. But as the generated code
is more compact than the manual check, a later patch will clean
up monitor.c to drop the redundancy added here.
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <1461879932-9020-9-git-send-email-eblake@redhat.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>
2016-04-29 00:45:16 +03:00
|
|
|
goto out;
|
|
|
|
}
|
2020-07-07 19:06:08 +03:00
|
|
|
if (visit_type_q_obj_my_command_arg_members(v, &arg, errp)) {
|
|
|
|
ok = visit_check_struct(v, errp);
|
qapi: Split visit_end_struct() into pieces
As mentioned in previous patches, we want to call visit_end_struct()
functions unconditionally, so that visitors can release resources
tied up since the matching visit_start_struct() without also having
to worry about error priority if more than one error occurs.
Even though error_propagate() can be safely used to ignore a second
error during cleanup caused by a first error, it is simpler if the
cleanup cannot set an error. So, split out the error checking
portion (basically, input visitors checking for unvisited keys) into
a new function visit_check_struct(), which can be safely skipped if
any earlier errors are encountered, and leave the cleanup portion
(which never fails, but must be called unconditionally if
visit_start_struct() succeeded) in visit_end_struct().
Generated code in qapi-visit.c has diffs resembling:
|@@ -59,10 +59,12 @@ void visit_type_ACPIOSTInfo(Visitor *v,
| goto out_obj;
| }
| visit_type_ACPIOSTInfo_members(v, obj, &err);
|- error_propagate(errp, err);
|- err = NULL;
|+ if (err) {
|+ goto out_obj;
|+ }
|+ visit_check_struct(v, &err);
| out_obj:
|- visit_end_struct(v, &err);
|+ visit_end_struct(v);
| out:
and in qapi-event.c:
@@ -47,7 +47,10 @@ void qapi_event_send_acpi_device_ost(ACP
| goto out;
| }
| visit_type_q_obj_ACPI_DEVICE_OST_arg_members(v, ¶m, &err);
|- visit_end_struct(v, err ? NULL : &err);
|+ if (!err) {
|+ visit_check_struct(v, &err);
|+ }
|+ visit_end_struct(v);
| if (err) {
| goto out;
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <1461879932-9020-20-git-send-email-eblake@redhat.com>
[Conflict with a doc fixup resolved]
Signed-off-by: Markus Armbruster <armbru@redhat.com>
2016-04-29 00:45:27 +03:00
|
|
|
}
|
qapi: Add parameter to visit_end_*
Rather than making the dealloc visitor track of stack of pointers
remembered during visit_start_* in order to free them during
visit_end_*, it's a lot easier to just make all callers pass the
same pointer to visit_end_*. The generated code has access to the
same pointer, while all other users are doing virtual walks and
can pass NULL. The dealloc visitor is then greatly simplified.
All three visit_end_*() functions intentionally take a void**,
even though the visit_start_*() functions differ between void**,
GenericList**, and GenericAlternate**. This is done for several
reasons: when doing a virtual walk, passing NULL doesn't care
what the type is, but when doing a generated walk, we already
have to cast the caller's specific FOO* to call visit_start,
while using void** lets us use visit_end without a cast. Also,
an upcoming patch will add a clone visitor that wants to use
the same implementation for all three visit_end callbacks,
which is made easier if all three share the same signature.
For visitors with already track per-object state (the QMP visitors
via a stack, and the string visitors which do not allow nesting),
add an assertion that the caller is indeed passing the same
pointer to paired calls.
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <1465490926-28625-4-git-send-email-eblake@redhat.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>
2016-06-09 19:48:34 +03:00
|
|
|
visit_end_struct(v, NULL);
|
2020-07-07 19:06:08 +03:00
|
|
|
if (!ok) {
|
2011-07-19 23:50:46 +04:00
|
|
|
goto out;
|
|
|
|
}
|
qapi: Replace uncommon use of the error API by the common one
We commonly use the error API like this:
err = NULL;
foo(..., &err);
if (err) {
goto out;
}
bar(..., &err);
Every error source is checked separately. The second function is only
called when the first one succeeds. Both functions are free to pass
their argument to error_set(). Because error_set() asserts no error
has been set, this effectively means they must not be called with an
error set.
The qapi-generated code uses the error API differently:
// *errp was initialized to NULL somewhere up the call chain
frob(..., errp);
gnat(..., errp);
Errors accumulate in *errp: first error wins, subsequent errors get
dropped. To make this work, the second function does nothing when
called with an error set. Requires non-null errp, or else the second
function can't see the first one fail.
This usage has also bled into visitor tests, and two device model
object property getters rtc_get_date() and balloon_stats_get_all().
With the "accumulate" technique, you need fewer error checks in
callers, and buy that with an error check in every callee. Can be
nice.
However, mixing the two techniques is confusing. You can't use the
"accumulate" technique with functions designed for the "check
separately" technique. You can use the "check separately" technique
with functions designed for the "accumulate" technique, but then
error_set() can't catch you setting an error more than once.
Standardize on the "check separately" technique for now, because it's
overwhelmingly prevalent.
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com>
2014-05-07 11:53:54 +04:00
|
|
|
|
2022-01-26 19:11:28 +03:00
|
|
|
if (trace_event_get_state_backends(TRACE_QMP_ENTER_MY_COMMAND)) {
|
|
|
|
g_autoptr(GString) req_json = qobject_to_json(QOBJECT(args));
|
|
|
|
|
|
|
|
trace_qmp_enter_my_command(req_json->str);
|
|
|
|
}
|
|
|
|
|
2017-08-24 11:45:56 +03:00
|
|
|
retval = qmp_my_command(arg.arg1, &err);
|
2015-09-30 01:21:08 +03:00
|
|
|
if (err) {
|
2022-01-26 19:11:28 +03:00
|
|
|
trace_qmp_exit_my_command(error_get_pretty(err), false);
|
2022-01-26 19:11:25 +03:00
|
|
|
error_propagate(errp, err);
|
qapi: Replace uncommon use of the error API by the common one
We commonly use the error API like this:
err = NULL;
foo(..., &err);
if (err) {
goto out;
}
bar(..., &err);
Every error source is checked separately. The second function is only
called when the first one succeeds. Both functions are free to pass
their argument to error_set(). Because error_set() asserts no error
has been set, this effectively means they must not be called with an
error set.
The qapi-generated code uses the error API differently:
// *errp was initialized to NULL somewhere up the call chain
frob(..., errp);
gnat(..., errp);
Errors accumulate in *errp: first error wins, subsequent errors get
dropped. To make this work, the second function does nothing when
called with an error set. Requires non-null errp, or else the second
function can't see the first one fail.
This usage has also bled into visitor tests, and two device model
object property getters rtc_get_date() and balloon_stats_get_all().
With the "accumulate" technique, you need fewer error checks in
callers, and buy that with an error check in every callee. Can be
nice.
However, mixing the two techniques is confusing. You can't use the
"accumulate" technique with functions designed for the "check
separately" technique. You can use the "check separately" technique
with functions designed for the "accumulate" technique, but then
error_set() can't catch you setting an error more than once.
Standardize on the "check separately" technique for now, because it's
overwhelmingly prevalent.
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com>
2014-05-07 11:53:54 +04:00
|
|
|
goto out;
|
2014-05-07 11:53:43 +04:00
|
|
|
}
|
2011-07-19 23:50:46 +04:00
|
|
|
|
2020-07-07 19:06:08 +03:00
|
|
|
qmp_marshal_output_UserDefOne(retval, ret, errp);
|
qapi: Replace uncommon use of the error API by the common one
We commonly use the error API like this:
err = NULL;
foo(..., &err);
if (err) {
goto out;
}
bar(..., &err);
Every error source is checked separately. The second function is only
called when the first one succeeds. Both functions are free to pass
their argument to error_set(). Because error_set() asserts no error
has been set, this effectively means they must not be called with an
error set.
The qapi-generated code uses the error API differently:
// *errp was initialized to NULL somewhere up the call chain
frob(..., errp);
gnat(..., errp);
Errors accumulate in *errp: first error wins, subsequent errors get
dropped. To make this work, the second function does nothing when
called with an error set. Requires non-null errp, or else the second
function can't see the first one fail.
This usage has also bled into visitor tests, and two device model
object property getters rtc_get_date() and balloon_stats_get_all().
With the "accumulate" technique, you need fewer error checks in
callers, and buy that with an error check in every callee. Can be
nice.
However, mixing the two techniques is confusing. You can't use the
"accumulate" technique with functions designed for the "check
separately" technique. You can use the "check separately" technique
with functions designed for the "accumulate" technique, but then
error_set() can't catch you setting an error more than once.
Standardize on the "check separately" technique for now, because it's
overwhelmingly prevalent.
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com>
2014-05-07 11:53:54 +04:00
|
|
|
|
2022-01-26 19:11:28 +03:00
|
|
|
if (trace_event_get_state_backends(TRACE_QMP_EXIT_MY_COMMAND)) {
|
|
|
|
g_autoptr(GString) ret_json = qobject_to_json(*ret);
|
|
|
|
|
|
|
|
trace_qmp_exit_my_command(ret_json->str, true);
|
|
|
|
}
|
|
|
|
|
2011-07-19 23:50:46 +04:00
|
|
|
out:
|
qapi: Add new visit_free() function
Making each visitor provide its own (awkwardly-named) FOO_cleanup()
is unusual, when we can instead have a polymorphic visit_free()
interface. Over the next few patches, we can use the polymorphic
functions to eliminate the need for a FOO_get_visitor() function
for accessing specific visitor functionality, once everything can
be accessed directly through the Visitor* interfaces.
The dealloc visitor is the first one converted to completely use
the new entry point, since qapi_dealloc_visitor_cleanup() was the
only reason that qapi_dealloc_get_visitor() existed, and only
generated and testsuite code was even using it. With the new
visit_free() entry point in place, we no longer need to expose
the QapiDeallocVisitor subtype through qapi_dealloc_visitor_new(),
and can get by with less generated code, with diffs that look like:
| void qapi_free_ACPIOSTInfo(ACPIOSTInfo *obj)
| {
|- QapiDeallocVisitor *qdv;
| Visitor *v;
|
| if (!obj) {
| return;
| }
|
|- qdv = qapi_dealloc_visitor_new();
|- v = qapi_dealloc_get_visitor(qdv);
|+ v = qapi_dealloc_visitor_new();
| visit_type_ACPIOSTInfo(v, NULL, &obj, NULL);
|- qapi_dealloc_visitor_cleanup(qdv);
|+ visit_free(v);
|}
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <1465490926-28625-5-git-send-email-eblake@redhat.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>
2016-06-09 19:48:35 +03:00
|
|
|
visit_free(v);
|
|
|
|
v = qapi_dealloc_visitor_new();
|
qapi-commands: Wrap argument visit in visit_start_struct
The qmp-input visitor was allowing callers to play rather fast
and loose: when visiting a QDict, you could grab members of the
root dictionary without first pushing into the dict; among the
culprit callers was the generated marshal code on the 'arguments'
dictionary of a QMP command. But we are about to tighten the
input visitor, at which point the generated marshal code MUST
follow the same paradigms as everyone else, of pushing into the
struct before grabbing its keys.
Generated code grows as follows:
|@@ -515,7 +641,12 @@ void qmp_marshal_blockdev_backup(QDict *
| BlockdevBackup arg = {0};
|
| v = qmp_input_get_visitor(qiv);
|+ visit_start_struct(v, NULL, NULL, 0, &err);
|+ if (err) {
|+ goto out;
|+ }
| visit_type_BlockdevBackup_members(v, &arg, &err);
|+ visit_end_struct(v, err ? NULL : &err);
| if (err) {
| goto out;
| }
|@@ -527,7 +715,9 @@ out:
| qmp_input_visitor_cleanup(qiv);
| qdv = qapi_dealloc_visitor_new();
| v = qapi_dealloc_get_visitor(qdv);
|+ visit_start_struct(v, NULL, NULL, 0, NULL);
| visit_type_BlockdevBackup_members(v, &arg, NULL);
|+ visit_end_struct(v, NULL);
| qapi_dealloc_visitor_cleanup(qdv);
| }
The use of 'err ? NULL : &err' is temporary; a later patch will
clean that up when it splits visit_end_struct().
Prior to this patch, the fact that there was no final
visit_end_struct() meant that even though we are using a strict
input visit, the marshalling code was not detecting excess input
at the top level (only in nested levels). Fortunately, we have
code in monitor.c:qmp_check_client_args() that also checks for
no excess arguments at the top level. But as the generated code
is more compact than the manual check, a later patch will clean
up monitor.c to drop the redundancy added here.
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <1461879932-9020-9-git-send-email-eblake@redhat.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>
2016-04-29 00:45:16 +03:00
|
|
|
visit_start_struct(v, NULL, NULL, 0, NULL);
|
2017-08-24 11:45:56 +03:00
|
|
|
visit_type_q_obj_my_command_arg_members(v, &arg, NULL);
|
qapi: Add parameter to visit_end_*
Rather than making the dealloc visitor track of stack of pointers
remembered during visit_start_* in order to free them during
visit_end_*, it's a lot easier to just make all callers pass the
same pointer to visit_end_*. The generated code has access to the
same pointer, while all other users are doing virtual walks and
can pass NULL. The dealloc visitor is then greatly simplified.
All three visit_end_*() functions intentionally take a void**,
even though the visit_start_*() functions differ between void**,
GenericList**, and GenericAlternate**. This is done for several
reasons: when doing a virtual walk, passing NULL doesn't care
what the type is, but when doing a generated walk, we already
have to cast the caller's specific FOO* to call visit_start,
while using void** lets us use visit_end without a cast. Also,
an upcoming patch will add a clone visitor that wants to use
the same implementation for all three visit_end callbacks,
which is made easier if all three share the same signature.
For visitors with already track per-object state (the QMP visitors
via a stack, and the string visitors which do not allow nesting),
add an assertion that the caller is indeed passing the same
pointer to paired calls.
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <1465490926-28625-4-git-send-email-eblake@redhat.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>
2016-06-09 19:48:34 +03:00
|
|
|
visit_end_struct(v, NULL);
|
qapi: Add new visit_free() function
Making each visitor provide its own (awkwardly-named) FOO_cleanup()
is unusual, when we can instead have a polymorphic visit_free()
interface. Over the next few patches, we can use the polymorphic
functions to eliminate the need for a FOO_get_visitor() function
for accessing specific visitor functionality, once everything can
be accessed directly through the Visitor* interfaces.
The dealloc visitor is the first one converted to completely use
the new entry point, since qapi_dealloc_visitor_cleanup() was the
only reason that qapi_dealloc_get_visitor() existed, and only
generated and testsuite code was even using it. With the new
visit_free() entry point in place, we no longer need to expose
the QapiDeallocVisitor subtype through qapi_dealloc_visitor_new(),
and can get by with less generated code, with diffs that look like:
| void qapi_free_ACPIOSTInfo(ACPIOSTInfo *obj)
| {
|- QapiDeallocVisitor *qdv;
| Visitor *v;
|
| if (!obj) {
| return;
| }
|
|- qdv = qapi_dealloc_visitor_new();
|- v = qapi_dealloc_get_visitor(qdv);
|+ v = qapi_dealloc_visitor_new();
| visit_type_ACPIOSTInfo(v, NULL, &obj, NULL);
|- qapi_dealloc_visitor_cleanup(qdv);
|+ visit_free(v);
|}
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <1465490926-28625-5-git-send-email-eblake@redhat.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>
2016-06-09 19:48:35 +03:00
|
|
|
visit_free(v);
|
2011-07-19 23:50:46 +04:00
|
|
|
}
|
2020-07-07 19:06:08 +03:00
|
|
|
|
2021-07-21 02:56:17 +03:00
|
|
|
[Uninteresting stuff omitted...]
|
2019-11-20 21:25:48 +03:00
|
|
|
$ cat qapi-generated/example-qapi-init-commands.h
|
2021-07-21 02:56:17 +03:00
|
|
|
[Uninteresting stuff omitted...]
|
2019-11-20 21:25:48 +03:00
|
|
|
#ifndef EXAMPLE_QAPI_INIT_COMMANDS_H
|
|
|
|
#define EXAMPLE_QAPI_INIT_COMMANDS_H
|
2011-07-19 23:50:46 +04:00
|
|
|
|
2019-11-20 21:25:48 +03:00
|
|
|
#include "qapi/qmp/dispatch.h"
|
|
|
|
|
|
|
|
void example_qmp_init_marshal(QmpCommandList *cmds);
|
|
|
|
|
|
|
|
#endif /* EXAMPLE_QAPI_INIT_COMMANDS_H */
|
|
|
|
$ cat qapi-generated/example-qapi-init-commands.c
|
2021-07-21 02:56:17 +03:00
|
|
|
[Uninteresting stuff omitted...]
|
2017-08-24 11:45:56 +03:00
|
|
|
void example_qmp_init_marshal(QmpCommandList *cmds)
|
2011-07-19 23:50:46 +04:00
|
|
|
{
|
2017-08-24 11:45:56 +03:00
|
|
|
QTAILQ_INIT(cmds);
|
2011-07-19 23:50:46 +04:00
|
|
|
|
2017-08-24 11:45:56 +03:00
|
|
|
qmp_register_command(cmds, "my-command",
|
2022-11-04 19:06:43 +03:00
|
|
|
qmp_marshal_my_command, 0, 0);
|
2017-08-24 11:45:56 +03:00
|
|
|
}
|
2021-07-21 02:56:17 +03:00
|
|
|
[Uninteresting stuff omitted...]
|
2018-08-28 15:07:36 +03:00
|
|
|
|
2021-07-21 02:56:19 +03:00
|
|
|
For a modular QAPI schema (see section `Include directives`_), code for
|
2021-07-21 02:56:17 +03:00
|
|
|
each sub-module SUBDIR/SUBMODULE.json is actually generated into::
|
2019-02-14 18:22:34 +03:00
|
|
|
|
2021-07-21 02:56:17 +03:00
|
|
|
SUBDIR/$(prefix)qapi-commands-SUBMODULE.h
|
|
|
|
SUBDIR/$(prefix)qapi-commands-SUBMODULE.c
|
2019-02-14 18:22:34 +03:00
|
|
|
|
2021-07-21 02:56:17 +03:00
|
|
|
|
|
|
|
Code generated for events
|
|
|
|
-------------------------
|
2014-09-26 19:20:33 +04:00
|
|
|
|
2018-02-26 22:48:58 +03:00
|
|
|
This is the code related to events defined in the schema, providing
|
|
|
|
qapi_event_send_EVENT().
|
|
|
|
|
|
|
|
The following files are created:
|
2014-09-26 19:20:33 +04:00
|
|
|
|
2021-07-21 02:56:17 +03:00
|
|
|
``$(prefix)qapi-events.h``
|
|
|
|
Function prototypes for each event type
|
2018-02-26 22:48:58 +03:00
|
|
|
|
2021-07-21 02:56:17 +03:00
|
|
|
``$(prefix)qapi-events.c``
|
|
|
|
Implementation of functions to send an event
|
2014-09-26 19:20:33 +04:00
|
|
|
|
2021-07-21 02:56:17 +03:00
|
|
|
``$(prefix)qapi-emit-events.h``
|
|
|
|
Enumeration of all event names, and common event code declarations
|
2019-02-14 18:22:38 +03:00
|
|
|
|
2021-07-21 02:56:17 +03:00
|
|
|
``$(prefix)qapi-emit-events.c``
|
|
|
|
Common event code definitions
|
2019-02-14 18:22:38 +03:00
|
|
|
|
2021-07-21 02:56:17 +03:00
|
|
|
Example::
|
2014-09-26 19:20:33 +04:00
|
|
|
|
2018-02-11 12:36:05 +03:00
|
|
|
$ cat qapi-generated/example-qapi-events.h
|
2021-07-21 02:56:17 +03:00
|
|
|
[Uninteresting stuff omitted...]
|
2016-03-03 19:16:46 +03:00
|
|
|
|
2018-08-28 15:07:36 +03:00
|
|
|
#ifndef EXAMPLE_QAPI_EVENTS_H
|
|
|
|
#define EXAMPLE_QAPI_EVENTS_H
|
2016-03-03 19:16:46 +03:00
|
|
|
|
2018-08-28 15:07:36 +03:00
|
|
|
#include "qapi/util.h"
|
2016-03-03 19:16:46 +03:00
|
|
|
#include "example-qapi-types.h"
|
|
|
|
|
2018-08-15 16:37:37 +03:00
|
|
|
void qapi_event_send_my_event(void);
|
2016-03-03 19:16:46 +03:00
|
|
|
|
2018-08-28 15:07:36 +03:00
|
|
|
#endif /* EXAMPLE_QAPI_EVENTS_H */
|
2018-02-11 12:36:05 +03:00
|
|
|
$ cat qapi-generated/example-qapi-events.c
|
2021-07-21 02:56:17 +03:00
|
|
|
[Uninteresting stuff omitted...]
|
2014-09-26 19:20:33 +04:00
|
|
|
|
2018-08-15 16:37:37 +03:00
|
|
|
void qapi_event_send_my_event(void)
|
2014-09-26 19:20:33 +04:00
|
|
|
{
|
|
|
|
QDict *qmp;
|
|
|
|
|
|
|
|
qmp = qmp_event_build_dict("MY_EVENT");
|
|
|
|
|
qapi: Eliminate indirection through qmp_event_get_func_emit()
The qapi_event_send_FOO() functions emit events like this:
QMPEventFuncEmit emit;
emit = qmp_event_get_func_emit();
if (!emit) {
return;
}
qmp = qmp_event_build_dict("FOO");
[put event arguments into @qmp...]
emit(QAPI_EVENT_FOO, qmp);
The value of qmp_event_get_func_emit() depends only on the program:
* In qemu-system-FOO, it's always monitor_qapi_event_queue.
* In tests/test-qmp-event, it's always event_test_emit.
* In all other programs, it's always null.
This is exactly the kind of dependence the linker is supposed to
resolve; we don't actually need an indirection.
Note that things would fall apart if we linked more than one QAPI
schema into a single program: each set of qapi_event_send_FOO() uses
its own event enumeration, yet they share a single emit function.
Which takes the event enumeration as an argument. Which one if
there's more than one?
More seriously: how does this work even now? qemu-system-FOO wants
QAPIEvent, and passes a function taking that to
qmp_event_set_func_emit(). test-qmp-event wants test_QAPIEvent, and
passes a function taking that to qmp_event_set_func_emit().
It works by type trickery, of course:
typedef void (*QMPEventFuncEmit)(unsigned event, QDict *dict);
void qmp_event_set_func_emit(QMPEventFuncEmit emit);
QMPEventFuncEmit qmp_event_get_func_emit(void);
We use unsigned instead of the enumeration type. Relies on both
enumerations boiling down to unsigned, which happens to be true for
the compilers we use.
Clean this up as follows:
* Generate qapi_event_send_FOO() that call PREFIX_qapi_event_emit()
instead of the value of qmp_event_set_func_emit().
* Generate a prototype for PREFIX_qapi_event_emit() into
qapi-events.h.
* PREFIX_ is empty for qapi/qapi-schema.json, and test_ for
tests/qapi-schema/qapi-schema-test.json. It's qga_ for
qga/qapi-schema.json, and doc-good- for
tests/qapi-schema/doc-good.json, but those don't define any events.
* Rename monitor_qapi_event_queue() to qapi_event_emit() instead of
passing it to qmp_event_set_func_emit(). This takes care of
qemu-system-FOO.
* Rename event_test_emit() to test_qapi_event_emit() instead of
passing it to qmp_event_set_func_emit(). This takes care of
tests/test-qmp-event.
* Add a qapi_event_emit() that does nothing to stubs/monitor.c. This
takes care of all other programs that link code emitting QMP events.
* Drop qmp_event_set_func_emit(), qmp_event_get_func_emit().
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Message-Id: <20181218182234.28876-3-armbru@redhat.com>
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
[Commit message typos fixed]
2018-12-18 21:22:21 +03:00
|
|
|
example_qapi_event_emit(EXAMPLE_QAPI_EVENT_MY_EVENT, qmp);
|
2014-09-26 19:20:33 +04:00
|
|
|
|
2018-04-19 18:01:43 +03:00
|
|
|
qobject_unref(qmp);
|
2014-09-26 19:20:33 +04:00
|
|
|
}
|
|
|
|
|
2021-07-21 02:56:17 +03:00
|
|
|
[Uninteresting stuff omitted...]
|
2019-02-14 18:22:38 +03:00
|
|
|
$ cat qapi-generated/example-qapi-emit-events.h
|
2021-07-21 02:56:17 +03:00
|
|
|
[Uninteresting stuff omitted...]
|
2019-02-14 18:22:38 +03:00
|
|
|
|
|
|
|
#ifndef EXAMPLE_QAPI_EMIT_EVENTS_H
|
|
|
|
#define EXAMPLE_QAPI_EMIT_EVENTS_H
|
|
|
|
|
|
|
|
#include "qapi/util.h"
|
|
|
|
|
|
|
|
typedef enum example_QAPIEvent {
|
|
|
|
EXAMPLE_QAPI_EVENT_MY_EVENT,
|
|
|
|
EXAMPLE_QAPI_EVENT__MAX,
|
|
|
|
} example_QAPIEvent;
|
|
|
|
|
|
|
|
#define example_QAPIEvent_str(val) \
|
|
|
|
qapi_enum_lookup(&example_QAPIEvent_lookup, (val))
|
|
|
|
|
|
|
|
extern const QEnumLookup example_QAPIEvent_lookup;
|
|
|
|
|
|
|
|
void example_qapi_event_emit(example_QAPIEvent event, QDict *qdict);
|
|
|
|
|
|
|
|
#endif /* EXAMPLE_QAPI_EMIT_EVENTS_H */
|
|
|
|
$ cat qapi-generated/example-qapi-emit-events.c
|
2021-07-21 02:56:17 +03:00
|
|
|
[Uninteresting stuff omitted...]
|
2019-02-14 18:22:38 +03:00
|
|
|
|
2018-02-26 22:48:58 +03:00
|
|
|
const QEnumLookup example_QAPIEvent_lookup = {
|
|
|
|
.array = (const char *const[]) {
|
|
|
|
[EXAMPLE_QAPI_EVENT_MY_EVENT] = "MY_EVENT",
|
|
|
|
},
|
|
|
|
.size = EXAMPLE_QAPI_EVENT__MAX
|
2014-09-26 19:20:33 +04:00
|
|
|
};
|
qapi: New QMP command query-qmp-schema for QMP introspection
qapi/introspect.json defines the introspection schema. It's designed
for QMP introspection, but should do for similar uses, such as QGA.
The introspection schema does not reflect all the rules and
restrictions that apply to QAPI schemata. A valid QAPI schema has an
introspection value conforming to the introspection schema, but the
converse is not true.
Introspection lowers away a number of schema details, and makes
implicit things explicit:
* The built-in types are declared with their JSON type.
All integer types are mapped to 'int', because how many bits we use
internally is an implementation detail. It could be pressed into
external interface service as very approximate range information,
but that's a bad idea. If we need range information, we better do
it properly.
* Implicit type definitions are made explicit, and given
auto-generated names:
- Array types, named by appending "List" to the name of their
element type, like in generated C.
- The enumeration types implicitly defined by simple union types,
named by appending "Kind" to the name of their simple union type,
like in generated C.
- Types that don't occur in generated C. Their names start with ':'
so they don't clash with the user's names.
* All type references are by name.
* The struct and union types are generalized into an object type.
* Base types are flattened.
* Commands take a single argument and return a single result.
Dictionary argument or list result is an implicit type definition.
The empty object type is used when a command takes no arguments or
produces no results.
The argument is always of object type, but the introspection schema
doesn't reflect that.
The 'gen': false directive is omitted as implementation detail.
The 'success-response' directive is omitted as well for now, even
though it's not an implementation detail, because it's not used by
QMP.
* Events carry a single data value.
Implicit type definition and empty object type use, just like for
commands.
The value is of object type, but the introspection schema doesn't
reflect that.
* Types not used by commands or events are omitted.
Indirect use counts as use.
* Optional members have a default, which can only be null right now
Instead of a mandatory "optional" flag, we have an optional default.
No default means mandatory, default null means optional without
default value. Non-null is available for optional with default
(possible future extension).
* Clients should *not* look up types by name, because type names are
not ABI. Look up the command or event you're interested in, then
follow the references.
TODO Should we hide the type names to eliminate the temptation?
New generator scripts/qapi-introspect.py computes an introspection
value for its input, and generates a C variable holding it.
It can generate awfully long lines. Marked TODO.
A new test-qmp-input-visitor test case feeds its result for both
tests/qapi-schema/qapi-schema-test.json and qapi-schema.json to a
QmpInputVisitor to verify it actually conforms to the schema.
New QMP command query-qmp-schema takes its return value from that
variable. Its reply is some 85KiBytes for me right now.
If this turns out to be too much, we have a couple of options:
* We can use shorter names in the JSON. Not the QMP style.
* Optionally return the sub-schema for commands and events given as
arguments.
Right now qmp_query_schema() sends the string literal computed by
qmp-introspect.py. To compute sub-schema at run time, we'd have to
duplicate parts of qapi-introspect.py in C. Unattractive.
* Let clients cache the output of query-qmp-schema.
It changes only on QEMU upgrades, i.e. rarely. Provide a command
query-qmp-schema-hash. Clients can have a cache indexed by hash,
and re-query the schema only when they don't have it cached. Even
simpler: put the hash in the QMP greeting.
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
2015-09-16 14:06:28 +03:00
|
|
|
|
2021-07-21 02:56:17 +03:00
|
|
|
[Uninteresting stuff omitted...]
|
2018-08-28 15:07:36 +03:00
|
|
|
|
2021-07-21 02:56:19 +03:00
|
|
|
For a modular QAPI schema (see section `Include directives`_), code for
|
2021-07-21 02:56:17 +03:00
|
|
|
each sub-module SUBDIR/SUBMODULE.json is actually generated into ::
|
|
|
|
|
|
|
|
SUBDIR/$(prefix)qapi-events-SUBMODULE.h
|
|
|
|
SUBDIR/$(prefix)qapi-events-SUBMODULE.c
|
2019-02-14 18:22:34 +03:00
|
|
|
|
|
|
|
|
2021-07-21 02:56:17 +03:00
|
|
|
Code generated for introspection
|
|
|
|
--------------------------------
|
qapi: New QMP command query-qmp-schema for QMP introspection
qapi/introspect.json defines the introspection schema. It's designed
for QMP introspection, but should do for similar uses, such as QGA.
The introspection schema does not reflect all the rules and
restrictions that apply to QAPI schemata. A valid QAPI schema has an
introspection value conforming to the introspection schema, but the
converse is not true.
Introspection lowers away a number of schema details, and makes
implicit things explicit:
* The built-in types are declared with their JSON type.
All integer types are mapped to 'int', because how many bits we use
internally is an implementation detail. It could be pressed into
external interface service as very approximate range information,
but that's a bad idea. If we need range information, we better do
it properly.
* Implicit type definitions are made explicit, and given
auto-generated names:
- Array types, named by appending "List" to the name of their
element type, like in generated C.
- The enumeration types implicitly defined by simple union types,
named by appending "Kind" to the name of their simple union type,
like in generated C.
- Types that don't occur in generated C. Their names start with ':'
so they don't clash with the user's names.
* All type references are by name.
* The struct and union types are generalized into an object type.
* Base types are flattened.
* Commands take a single argument and return a single result.
Dictionary argument or list result is an implicit type definition.
The empty object type is used when a command takes no arguments or
produces no results.
The argument is always of object type, but the introspection schema
doesn't reflect that.
The 'gen': false directive is omitted as implementation detail.
The 'success-response' directive is omitted as well for now, even
though it's not an implementation detail, because it's not used by
QMP.
* Events carry a single data value.
Implicit type definition and empty object type use, just like for
commands.
The value is of object type, but the introspection schema doesn't
reflect that.
* Types not used by commands or events are omitted.
Indirect use counts as use.
* Optional members have a default, which can only be null right now
Instead of a mandatory "optional" flag, we have an optional default.
No default means mandatory, default null means optional without
default value. Non-null is available for optional with default
(possible future extension).
* Clients should *not* look up types by name, because type names are
not ABI. Look up the command or event you're interested in, then
follow the references.
TODO Should we hide the type names to eliminate the temptation?
New generator scripts/qapi-introspect.py computes an introspection
value for its input, and generates a C variable holding it.
It can generate awfully long lines. Marked TODO.
A new test-qmp-input-visitor test case feeds its result for both
tests/qapi-schema/qapi-schema-test.json and qapi-schema.json to a
QmpInputVisitor to verify it actually conforms to the schema.
New QMP command query-qmp-schema takes its return value from that
variable. Its reply is some 85KiBytes for me right now.
If this turns out to be too much, we have a couple of options:
* We can use shorter names in the JSON. Not the QMP style.
* Optionally return the sub-schema for commands and events given as
arguments.
Right now qmp_query_schema() sends the string literal computed by
qmp-introspect.py. To compute sub-schema at run time, we'd have to
duplicate parts of qapi-introspect.py in C. Unattractive.
* Let clients cache the output of query-qmp-schema.
It changes only on QEMU upgrades, i.e. rarely. Provide a command
query-qmp-schema-hash. Clients can have a cache indexed by hash,
and re-query the schema only when they don't have it cached. Even
simpler: put the hash in the QMP greeting.
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
2015-09-16 14:06:28 +03:00
|
|
|
|
2018-02-26 22:48:58 +03:00
|
|
|
The following files are created:
|
qapi: New QMP command query-qmp-schema for QMP introspection
qapi/introspect.json defines the introspection schema. It's designed
for QMP introspection, but should do for similar uses, such as QGA.
The introspection schema does not reflect all the rules and
restrictions that apply to QAPI schemata. A valid QAPI schema has an
introspection value conforming to the introspection schema, but the
converse is not true.
Introspection lowers away a number of schema details, and makes
implicit things explicit:
* The built-in types are declared with their JSON type.
All integer types are mapped to 'int', because how many bits we use
internally is an implementation detail. It could be pressed into
external interface service as very approximate range information,
but that's a bad idea. If we need range information, we better do
it properly.
* Implicit type definitions are made explicit, and given
auto-generated names:
- Array types, named by appending "List" to the name of their
element type, like in generated C.
- The enumeration types implicitly defined by simple union types,
named by appending "Kind" to the name of their simple union type,
like in generated C.
- Types that don't occur in generated C. Their names start with ':'
so they don't clash with the user's names.
* All type references are by name.
* The struct and union types are generalized into an object type.
* Base types are flattened.
* Commands take a single argument and return a single result.
Dictionary argument or list result is an implicit type definition.
The empty object type is used when a command takes no arguments or
produces no results.
The argument is always of object type, but the introspection schema
doesn't reflect that.
The 'gen': false directive is omitted as implementation detail.
The 'success-response' directive is omitted as well for now, even
though it's not an implementation detail, because it's not used by
QMP.
* Events carry a single data value.
Implicit type definition and empty object type use, just like for
commands.
The value is of object type, but the introspection schema doesn't
reflect that.
* Types not used by commands or events are omitted.
Indirect use counts as use.
* Optional members have a default, which can only be null right now
Instead of a mandatory "optional" flag, we have an optional default.
No default means mandatory, default null means optional without
default value. Non-null is available for optional with default
(possible future extension).
* Clients should *not* look up types by name, because type names are
not ABI. Look up the command or event you're interested in, then
follow the references.
TODO Should we hide the type names to eliminate the temptation?
New generator scripts/qapi-introspect.py computes an introspection
value for its input, and generates a C variable holding it.
It can generate awfully long lines. Marked TODO.
A new test-qmp-input-visitor test case feeds its result for both
tests/qapi-schema/qapi-schema-test.json and qapi-schema.json to a
QmpInputVisitor to verify it actually conforms to the schema.
New QMP command query-qmp-schema takes its return value from that
variable. Its reply is some 85KiBytes for me right now.
If this turns out to be too much, we have a couple of options:
* We can use shorter names in the JSON. Not the QMP style.
* Optionally return the sub-schema for commands and events given as
arguments.
Right now qmp_query_schema() sends the string literal computed by
qmp-introspect.py. To compute sub-schema at run time, we'd have to
duplicate parts of qapi-introspect.py in C. Unattractive.
* Let clients cache the output of query-qmp-schema.
It changes only on QEMU upgrades, i.e. rarely. Provide a command
query-qmp-schema-hash. Clients can have a cache indexed by hash,
and re-query the schema only when they don't have it cached. Even
simpler: put the hash in the QMP greeting.
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
2015-09-16 14:06:28 +03:00
|
|
|
|
2021-07-21 02:56:17 +03:00
|
|
|
``$(prefix)qapi-introspect.c``
|
|
|
|
Defines a string holding a JSON description of the schema
|
2018-02-26 22:48:58 +03:00
|
|
|
|
2021-07-21 02:56:17 +03:00
|
|
|
``$(prefix)qapi-introspect.h``
|
|
|
|
Declares the above string
|
qapi: New QMP command query-qmp-schema for QMP introspection
qapi/introspect.json defines the introspection schema. It's designed
for QMP introspection, but should do for similar uses, such as QGA.
The introspection schema does not reflect all the rules and
restrictions that apply to QAPI schemata. A valid QAPI schema has an
introspection value conforming to the introspection schema, but the
converse is not true.
Introspection lowers away a number of schema details, and makes
implicit things explicit:
* The built-in types are declared with their JSON type.
All integer types are mapped to 'int', because how many bits we use
internally is an implementation detail. It could be pressed into
external interface service as very approximate range information,
but that's a bad idea. If we need range information, we better do
it properly.
* Implicit type definitions are made explicit, and given
auto-generated names:
- Array types, named by appending "List" to the name of their
element type, like in generated C.
- The enumeration types implicitly defined by simple union types,
named by appending "Kind" to the name of their simple union type,
like in generated C.
- Types that don't occur in generated C. Their names start with ':'
so they don't clash with the user's names.
* All type references are by name.
* The struct and union types are generalized into an object type.
* Base types are flattened.
* Commands take a single argument and return a single result.
Dictionary argument or list result is an implicit type definition.
The empty object type is used when a command takes no arguments or
produces no results.
The argument is always of object type, but the introspection schema
doesn't reflect that.
The 'gen': false directive is omitted as implementation detail.
The 'success-response' directive is omitted as well for now, even
though it's not an implementation detail, because it's not used by
QMP.
* Events carry a single data value.
Implicit type definition and empty object type use, just like for
commands.
The value is of object type, but the introspection schema doesn't
reflect that.
* Types not used by commands or events are omitted.
Indirect use counts as use.
* Optional members have a default, which can only be null right now
Instead of a mandatory "optional" flag, we have an optional default.
No default means mandatory, default null means optional without
default value. Non-null is available for optional with default
(possible future extension).
* Clients should *not* look up types by name, because type names are
not ABI. Look up the command or event you're interested in, then
follow the references.
TODO Should we hide the type names to eliminate the temptation?
New generator scripts/qapi-introspect.py computes an introspection
value for its input, and generates a C variable holding it.
It can generate awfully long lines. Marked TODO.
A new test-qmp-input-visitor test case feeds its result for both
tests/qapi-schema/qapi-schema-test.json and qapi-schema.json to a
QmpInputVisitor to verify it actually conforms to the schema.
New QMP command query-qmp-schema takes its return value from that
variable. Its reply is some 85KiBytes for me right now.
If this turns out to be too much, we have a couple of options:
* We can use shorter names in the JSON. Not the QMP style.
* Optionally return the sub-schema for commands and events given as
arguments.
Right now qmp_query_schema() sends the string literal computed by
qmp-introspect.py. To compute sub-schema at run time, we'd have to
duplicate parts of qapi-introspect.py in C. Unattractive.
* Let clients cache the output of query-qmp-schema.
It changes only on QEMU upgrades, i.e. rarely. Provide a command
query-qmp-schema-hash. Clients can have a cache indexed by hash,
and re-query the schema only when they don't have it cached. Even
simpler: put the hash in the QMP greeting.
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
2015-09-16 14:06:28 +03:00
|
|
|
|
2021-07-21 02:56:17 +03:00
|
|
|
Example::
|
qapi: New QMP command query-qmp-schema for QMP introspection
qapi/introspect.json defines the introspection schema. It's designed
for QMP introspection, but should do for similar uses, such as QGA.
The introspection schema does not reflect all the rules and
restrictions that apply to QAPI schemata. A valid QAPI schema has an
introspection value conforming to the introspection schema, but the
converse is not true.
Introspection lowers away a number of schema details, and makes
implicit things explicit:
* The built-in types are declared with their JSON type.
All integer types are mapped to 'int', because how many bits we use
internally is an implementation detail. It could be pressed into
external interface service as very approximate range information,
but that's a bad idea. If we need range information, we better do
it properly.
* Implicit type definitions are made explicit, and given
auto-generated names:
- Array types, named by appending "List" to the name of their
element type, like in generated C.
- The enumeration types implicitly defined by simple union types,
named by appending "Kind" to the name of their simple union type,
like in generated C.
- Types that don't occur in generated C. Their names start with ':'
so they don't clash with the user's names.
* All type references are by name.
* The struct and union types are generalized into an object type.
* Base types are flattened.
* Commands take a single argument and return a single result.
Dictionary argument or list result is an implicit type definition.
The empty object type is used when a command takes no arguments or
produces no results.
The argument is always of object type, but the introspection schema
doesn't reflect that.
The 'gen': false directive is omitted as implementation detail.
The 'success-response' directive is omitted as well for now, even
though it's not an implementation detail, because it's not used by
QMP.
* Events carry a single data value.
Implicit type definition and empty object type use, just like for
commands.
The value is of object type, but the introspection schema doesn't
reflect that.
* Types not used by commands or events are omitted.
Indirect use counts as use.
* Optional members have a default, which can only be null right now
Instead of a mandatory "optional" flag, we have an optional default.
No default means mandatory, default null means optional without
default value. Non-null is available for optional with default
(possible future extension).
* Clients should *not* look up types by name, because type names are
not ABI. Look up the command or event you're interested in, then
follow the references.
TODO Should we hide the type names to eliminate the temptation?
New generator scripts/qapi-introspect.py computes an introspection
value for its input, and generates a C variable holding it.
It can generate awfully long lines. Marked TODO.
A new test-qmp-input-visitor test case feeds its result for both
tests/qapi-schema/qapi-schema-test.json and qapi-schema.json to a
QmpInputVisitor to verify it actually conforms to the schema.
New QMP command query-qmp-schema takes its return value from that
variable. Its reply is some 85KiBytes for me right now.
If this turns out to be too much, we have a couple of options:
* We can use shorter names in the JSON. Not the QMP style.
* Optionally return the sub-schema for commands and events given as
arguments.
Right now qmp_query_schema() sends the string literal computed by
qmp-introspect.py. To compute sub-schema at run time, we'd have to
duplicate parts of qapi-introspect.py in C. Unattractive.
* Let clients cache the output of query-qmp-schema.
It changes only on QEMU upgrades, i.e. rarely. Provide a command
query-qmp-schema-hash. Clients can have a cache indexed by hash,
and re-query the schema only when they don't have it cached. Even
simpler: put the hash in the QMP greeting.
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
2015-09-16 14:06:28 +03:00
|
|
|
|
2018-02-11 12:36:05 +03:00
|
|
|
$ cat qapi-generated/example-qapi-introspect.h
|
2021-07-21 02:56:17 +03:00
|
|
|
[Uninteresting stuff omitted...]
|
qapi: New QMP command query-qmp-schema for QMP introspection
qapi/introspect.json defines the introspection schema. It's designed
for QMP introspection, but should do for similar uses, such as QGA.
The introspection schema does not reflect all the rules and
restrictions that apply to QAPI schemata. A valid QAPI schema has an
introspection value conforming to the introspection schema, but the
converse is not true.
Introspection lowers away a number of schema details, and makes
implicit things explicit:
* The built-in types are declared with their JSON type.
All integer types are mapped to 'int', because how many bits we use
internally is an implementation detail. It could be pressed into
external interface service as very approximate range information,
but that's a bad idea. If we need range information, we better do
it properly.
* Implicit type definitions are made explicit, and given
auto-generated names:
- Array types, named by appending "List" to the name of their
element type, like in generated C.
- The enumeration types implicitly defined by simple union types,
named by appending "Kind" to the name of their simple union type,
like in generated C.
- Types that don't occur in generated C. Their names start with ':'
so they don't clash with the user's names.
* All type references are by name.
* The struct and union types are generalized into an object type.
* Base types are flattened.
* Commands take a single argument and return a single result.
Dictionary argument or list result is an implicit type definition.
The empty object type is used when a command takes no arguments or
produces no results.
The argument is always of object type, but the introspection schema
doesn't reflect that.
The 'gen': false directive is omitted as implementation detail.
The 'success-response' directive is omitted as well for now, even
though it's not an implementation detail, because it's not used by
QMP.
* Events carry a single data value.
Implicit type definition and empty object type use, just like for
commands.
The value is of object type, but the introspection schema doesn't
reflect that.
* Types not used by commands or events are omitted.
Indirect use counts as use.
* Optional members have a default, which can only be null right now
Instead of a mandatory "optional" flag, we have an optional default.
No default means mandatory, default null means optional without
default value. Non-null is available for optional with default
(possible future extension).
* Clients should *not* look up types by name, because type names are
not ABI. Look up the command or event you're interested in, then
follow the references.
TODO Should we hide the type names to eliminate the temptation?
New generator scripts/qapi-introspect.py computes an introspection
value for its input, and generates a C variable holding it.
It can generate awfully long lines. Marked TODO.
A new test-qmp-input-visitor test case feeds its result for both
tests/qapi-schema/qapi-schema-test.json and qapi-schema.json to a
QmpInputVisitor to verify it actually conforms to the schema.
New QMP command query-qmp-schema takes its return value from that
variable. Its reply is some 85KiBytes for me right now.
If this turns out to be too much, we have a couple of options:
* We can use shorter names in the JSON. Not the QMP style.
* Optionally return the sub-schema for commands and events given as
arguments.
Right now qmp_query_schema() sends the string literal computed by
qmp-introspect.py. To compute sub-schema at run time, we'd have to
duplicate parts of qapi-introspect.py in C. Unattractive.
* Let clients cache the output of query-qmp-schema.
It changes only on QEMU upgrades, i.e. rarely. Provide a command
query-qmp-schema-hash. Clients can have a cache indexed by hash,
and re-query the schema only when they don't have it cached. Even
simpler: put the hash in the QMP greeting.
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
2015-09-16 14:06:28 +03:00
|
|
|
|
2018-08-28 15:07:36 +03:00
|
|
|
#ifndef EXAMPLE_QAPI_INTROSPECT_H
|
|
|
|
#define EXAMPLE_QAPI_INTROSPECT_H
|
qapi: New QMP command query-qmp-schema for QMP introspection
qapi/introspect.json defines the introspection schema. It's designed
for QMP introspection, but should do for similar uses, such as QGA.
The introspection schema does not reflect all the rules and
restrictions that apply to QAPI schemata. A valid QAPI schema has an
introspection value conforming to the introspection schema, but the
converse is not true.
Introspection lowers away a number of schema details, and makes
implicit things explicit:
* The built-in types are declared with their JSON type.
All integer types are mapped to 'int', because how many bits we use
internally is an implementation detail. It could be pressed into
external interface service as very approximate range information,
but that's a bad idea. If we need range information, we better do
it properly.
* Implicit type definitions are made explicit, and given
auto-generated names:
- Array types, named by appending "List" to the name of their
element type, like in generated C.
- The enumeration types implicitly defined by simple union types,
named by appending "Kind" to the name of their simple union type,
like in generated C.
- Types that don't occur in generated C. Their names start with ':'
so they don't clash with the user's names.
* All type references are by name.
* The struct and union types are generalized into an object type.
* Base types are flattened.
* Commands take a single argument and return a single result.
Dictionary argument or list result is an implicit type definition.
The empty object type is used when a command takes no arguments or
produces no results.
The argument is always of object type, but the introspection schema
doesn't reflect that.
The 'gen': false directive is omitted as implementation detail.
The 'success-response' directive is omitted as well for now, even
though it's not an implementation detail, because it's not used by
QMP.
* Events carry a single data value.
Implicit type definition and empty object type use, just like for
commands.
The value is of object type, but the introspection schema doesn't
reflect that.
* Types not used by commands or events are omitted.
Indirect use counts as use.
* Optional members have a default, which can only be null right now
Instead of a mandatory "optional" flag, we have an optional default.
No default means mandatory, default null means optional without
default value. Non-null is available for optional with default
(possible future extension).
* Clients should *not* look up types by name, because type names are
not ABI. Look up the command or event you're interested in, then
follow the references.
TODO Should we hide the type names to eliminate the temptation?
New generator scripts/qapi-introspect.py computes an introspection
value for its input, and generates a C variable holding it.
It can generate awfully long lines. Marked TODO.
A new test-qmp-input-visitor test case feeds its result for both
tests/qapi-schema/qapi-schema-test.json and qapi-schema.json to a
QmpInputVisitor to verify it actually conforms to the schema.
New QMP command query-qmp-schema takes its return value from that
variable. Its reply is some 85KiBytes for me right now.
If this turns out to be too much, we have a couple of options:
* We can use shorter names in the JSON. Not the QMP style.
* Optionally return the sub-schema for commands and events given as
arguments.
Right now qmp_query_schema() sends the string literal computed by
qmp-introspect.py. To compute sub-schema at run time, we'd have to
duplicate parts of qapi-introspect.py in C. Unattractive.
* Let clients cache the output of query-qmp-schema.
It changes only on QEMU upgrades, i.e. rarely. Provide a command
query-qmp-schema-hash. Clients can have a cache indexed by hash,
and re-query the schema only when they don't have it cached. Even
simpler: put the hash in the QMP greeting.
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
2015-09-16 14:06:28 +03:00
|
|
|
|
2018-08-28 15:07:36 +03:00
|
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|
#include "qapi/qmp/qlit.h"
|
qapi: New QMP command query-qmp-schema for QMP introspection
qapi/introspect.json defines the introspection schema. It's designed
for QMP introspection, but should do for similar uses, such as QGA.
The introspection schema does not reflect all the rules and
restrictions that apply to QAPI schemata. A valid QAPI schema has an
introspection value conforming to the introspection schema, but the
converse is not true.
Introspection lowers away a number of schema details, and makes
implicit things explicit:
* The built-in types are declared with their JSON type.
All integer types are mapped to 'int', because how many bits we use
internally is an implementation detail. It could be pressed into
external interface service as very approximate range information,
but that's a bad idea. If we need range information, we better do
it properly.
* Implicit type definitions are made explicit, and given
auto-generated names:
- Array types, named by appending "List" to the name of their
element type, like in generated C.
- The enumeration types implicitly defined by simple union types,
named by appending "Kind" to the name of their simple union type,
like in generated C.
- Types that don't occur in generated C. Their names start with ':'
so they don't clash with the user's names.
* All type references are by name.
* The struct and union types are generalized into an object type.
* Base types are flattened.
* Commands take a single argument and return a single result.
Dictionary argument or list result is an implicit type definition.
The empty object type is used when a command takes no arguments or
produces no results.
The argument is always of object type, but the introspection schema
doesn't reflect that.
The 'gen': false directive is omitted as implementation detail.
The 'success-response' directive is omitted as well for now, even
though it's not an implementation detail, because it's not used by
QMP.
* Events carry a single data value.
Implicit type definition and empty object type use, just like for
commands.
The value is of object type, but the introspection schema doesn't
reflect that.
* Types not used by commands or events are omitted.
Indirect use counts as use.
* Optional members have a default, which can only be null right now
Instead of a mandatory "optional" flag, we have an optional default.
No default means mandatory, default null means optional without
default value. Non-null is available for optional with default
(possible future extension).
* Clients should *not* look up types by name, because type names are
not ABI. Look up the command or event you're interested in, then
follow the references.
TODO Should we hide the type names to eliminate the temptation?
New generator scripts/qapi-introspect.py computes an introspection
value for its input, and generates a C variable holding it.
It can generate awfully long lines. Marked TODO.
A new test-qmp-input-visitor test case feeds its result for both
tests/qapi-schema/qapi-schema-test.json and qapi-schema.json to a
QmpInputVisitor to verify it actually conforms to the schema.
New QMP command query-qmp-schema takes its return value from that
variable. Its reply is some 85KiBytes for me right now.
If this turns out to be too much, we have a couple of options:
* We can use shorter names in the JSON. Not the QMP style.
* Optionally return the sub-schema for commands and events given as
arguments.
Right now qmp_query_schema() sends the string literal computed by
qmp-introspect.py. To compute sub-schema at run time, we'd have to
duplicate parts of qapi-introspect.py in C. Unattractive.
* Let clients cache the output of query-qmp-schema.
It changes only on QEMU upgrades, i.e. rarely. Provide a command
query-qmp-schema-hash. Clients can have a cache indexed by hash,
and re-query the schema only when they don't have it cached. Even
simpler: put the hash in the QMP greeting.
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
2015-09-16 14:06:28 +03:00
|
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|
2018-08-28 15:07:36 +03:00
|
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extern const QLitObject example_qmp_schema_qlit;
|
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|
|
|
|
|
#endif /* EXAMPLE_QAPI_INTROSPECT_H */
|
2018-02-11 12:36:05 +03:00
|
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|
$ cat qapi-generated/example-qapi-introspect.c
|
2021-07-21 02:56:17 +03:00
|
|
|
[Uninteresting stuff omitted...]
|
2016-03-03 19:16:46 +03:00
|
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|
2018-03-05 20:29:51 +03:00
|
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|
const QLitObject example_qmp_schema_qlit = QLIT_QLIST(((QLitObject[]) {
|
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QLIT_QDICT(((QLitDictEntry[]) {
|
2018-08-28 15:07:36 +03:00
|
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|
{ "arg-type", QLIT_QSTR("0"), },
|
|
|
|
{ "meta-type", QLIT_QSTR("command"), },
|
|
|
|
{ "name", QLIT_QSTR("my-command"), },
|
|
|
|
{ "ret-type", QLIT_QSTR("1"), },
|
|
|
|
{}
|
|
|
|
})),
|
|
|
|
QLIT_QDICT(((QLitDictEntry[]) {
|
|
|
|
{ "arg-type", QLIT_QSTR("2"), },
|
|
|
|
{ "meta-type", QLIT_QSTR("event"), },
|
|
|
|
{ "name", QLIT_QSTR("MY_EVENT"), },
|
|
|
|
{}
|
2018-03-05 20:29:51 +03:00
|
|
|
})),
|
qapi: Add comments to aid debugging generated introspection
We consciously chose in commit 1a9a507b to hide QAPI type names
from the introspection output on the wire, but added a command
line option -u to unmask the type name when doing a debug build.
The unmask option still remains useful to some other forms of
automated analysis, so it will not be removed; however, when it
is not in use, the generated .c file can be hard to read. At
the time when we first introduced masking, the generated file
consisted only of a monolithic C string, so there was no clean
way to inject any comments.
Later, in commit 7d0f982b, we switched the generation to output
a QLit object, in part to make it easier for future addition of
conditional compilation. In fact, commit d626b6c1 took advantage
of this by passing a tuple instead of a bare object for encoding
the output of conditionals. By extending that tuple, we can now
interject strategic comments.
For now, type name debug aid comments are only output once per
meta-type, rather than at all uses of the number used to encode
the type within the introspection data. But this is still a lot
more convenient than having to regenerate the file with the
unmask operation temporarily turned on - merely search the
generated file for '"NNN" =' to learn the corresponding source
name and associated definition of type NNN.
The generated qapi-introspect.c changes only with the addition
of comments, such as:
| @@ -14755,6 +15240,7 @@
| { "name", QLIT_QSTR("[485]"), },
| {}
| })),
| + /* "485" = QCryptoBlockInfoLUKSSlot */
| QLIT_QDICT(((QLitDictEntry[]) {
| { "members", QLIT_QLIST(((QLitObject[]) {
| QLIT_QDICT(((QLitDictEntry[]) {
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <20180827213943.33524-3-eblake@redhat.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
[Rebased, update to qapi-code-gen.txt corrected]
Signed-off-by: Markus Armbruster <armbru@redhat.com>
2018-08-28 00:39:43 +03:00
|
|
|
/* "0" = q_obj_my-command-arg */
|
2018-03-05 20:29:51 +03:00
|
|
|
QLIT_QDICT(((QLitDictEntry[]) {
|
|
|
|
{ "members", QLIT_QLIST(((QLitObject[]) {
|
2018-08-28 15:07:36 +03:00
|
|
|
QLIT_QDICT(((QLitDictEntry[]) {
|
|
|
|
{ "name", QLIT_QSTR("arg1"), },
|
|
|
|
{ "type", QLIT_QSTR("[1]"), },
|
|
|
|
{}
|
|
|
|
})),
|
|
|
|
{}
|
|
|
|
})), },
|
|
|
|
{ "meta-type", QLIT_QSTR("object"), },
|
|
|
|
{ "name", QLIT_QSTR("0"), },
|
|
|
|
{}
|
2018-03-05 20:29:51 +03:00
|
|
|
})),
|
qapi: Add comments to aid debugging generated introspection
We consciously chose in commit 1a9a507b to hide QAPI type names
from the introspection output on the wire, but added a command
line option -u to unmask the type name when doing a debug build.
The unmask option still remains useful to some other forms of
automated analysis, so it will not be removed; however, when it
is not in use, the generated .c file can be hard to read. At
the time when we first introduced masking, the generated file
consisted only of a monolithic C string, so there was no clean
way to inject any comments.
Later, in commit 7d0f982b, we switched the generation to output
a QLit object, in part to make it easier for future addition of
conditional compilation. In fact, commit d626b6c1 took advantage
of this by passing a tuple instead of a bare object for encoding
the output of conditionals. By extending that tuple, we can now
interject strategic comments.
For now, type name debug aid comments are only output once per
meta-type, rather than at all uses of the number used to encode
the type within the introspection data. But this is still a lot
more convenient than having to regenerate the file with the
unmask operation temporarily turned on - merely search the
generated file for '"NNN" =' to learn the corresponding source
name and associated definition of type NNN.
The generated qapi-introspect.c changes only with the addition
of comments, such as:
| @@ -14755,6 +15240,7 @@
| { "name", QLIT_QSTR("[485]"), },
| {}
| })),
| + /* "485" = QCryptoBlockInfoLUKSSlot */
| QLIT_QDICT(((QLitDictEntry[]) {
| { "members", QLIT_QLIST(((QLitObject[]) {
| QLIT_QDICT(((QLitDictEntry[]) {
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <20180827213943.33524-3-eblake@redhat.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
[Rebased, update to qapi-code-gen.txt corrected]
Signed-off-by: Markus Armbruster <armbru@redhat.com>
2018-08-28 00:39:43 +03:00
|
|
|
/* "1" = UserDefOne */
|
2018-08-28 15:07:36 +03:00
|
|
|
QLIT_QDICT(((QLitDictEntry[]) {
|
|
|
|
{ "members", QLIT_QLIST(((QLitObject[]) {
|
|
|
|
QLIT_QDICT(((QLitDictEntry[]) {
|
|
|
|
{ "name", QLIT_QSTR("integer"), },
|
|
|
|
{ "type", QLIT_QSTR("int"), },
|
|
|
|
{}
|
|
|
|
})),
|
|
|
|
QLIT_QDICT(((QLitDictEntry[]) {
|
|
|
|
{ "default", QLIT_QNULL, },
|
|
|
|
{ "name", QLIT_QSTR("string"), },
|
|
|
|
{ "type", QLIT_QSTR("str"), },
|
|
|
|
{}
|
|
|
|
})),
|
2022-11-04 19:06:45 +03:00
|
|
|
QLIT_QDICT(((QLitDictEntry[]) {
|
|
|
|
{ "default", QLIT_QNULL, },
|
|
|
|
{ "name", QLIT_QSTR("flag"), },
|
|
|
|
{ "type", QLIT_QSTR("bool"), },
|
|
|
|
{}
|
|
|
|
})),
|
2018-08-28 15:07:36 +03:00
|
|
|
{}
|
|
|
|
})), },
|
|
|
|
{ "meta-type", QLIT_QSTR("object"), },
|
|
|
|
{ "name", QLIT_QSTR("1"), },
|
|
|
|
{}
|
|
|
|
})),
|
qapi: Add comments to aid debugging generated introspection
We consciously chose in commit 1a9a507b to hide QAPI type names
from the introspection output on the wire, but added a command
line option -u to unmask the type name when doing a debug build.
The unmask option still remains useful to some other forms of
automated analysis, so it will not be removed; however, when it
is not in use, the generated .c file can be hard to read. At
the time when we first introduced masking, the generated file
consisted only of a monolithic C string, so there was no clean
way to inject any comments.
Later, in commit 7d0f982b, we switched the generation to output
a QLit object, in part to make it easier for future addition of
conditional compilation. In fact, commit d626b6c1 took advantage
of this by passing a tuple instead of a bare object for encoding
the output of conditionals. By extending that tuple, we can now
interject strategic comments.
For now, type name debug aid comments are only output once per
meta-type, rather than at all uses of the number used to encode
the type within the introspection data. But this is still a lot
more convenient than having to regenerate the file with the
unmask operation temporarily turned on - merely search the
generated file for '"NNN" =' to learn the corresponding source
name and associated definition of type NNN.
The generated qapi-introspect.c changes only with the addition
of comments, such as:
| @@ -14755,6 +15240,7 @@
| { "name", QLIT_QSTR("[485]"), },
| {}
| })),
| + /* "485" = QCryptoBlockInfoLUKSSlot */
| QLIT_QDICT(((QLitDictEntry[]) {
| { "members", QLIT_QLIST(((QLitObject[]) {
| QLIT_QDICT(((QLitDictEntry[]) {
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <20180827213943.33524-3-eblake@redhat.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
[Rebased, update to qapi-code-gen.txt corrected]
Signed-off-by: Markus Armbruster <armbru@redhat.com>
2018-08-28 00:39:43 +03:00
|
|
|
/* "2" = q_empty */
|
2018-08-28 15:07:36 +03:00
|
|
|
QLIT_QDICT(((QLitDictEntry[]) {
|
|
|
|
{ "members", QLIT_QLIST(((QLitObject[]) {
|
|
|
|
{}
|
|
|
|
})), },
|
|
|
|
{ "meta-type", QLIT_QSTR("object"), },
|
|
|
|
{ "name", QLIT_QSTR("2"), },
|
|
|
|
{}
|
|
|
|
})),
|
|
|
|
QLIT_QDICT(((QLitDictEntry[]) {
|
|
|
|
{ "element-type", QLIT_QSTR("1"), },
|
|
|
|
{ "meta-type", QLIT_QSTR("array"), },
|
|
|
|
{ "name", QLIT_QSTR("[1]"), },
|
|
|
|
{}
|
|
|
|
})),
|
|
|
|
QLIT_QDICT(((QLitDictEntry[]) {
|
|
|
|
{ "json-type", QLIT_QSTR("int"), },
|
|
|
|
{ "meta-type", QLIT_QSTR("builtin"), },
|
|
|
|
{ "name", QLIT_QSTR("int"), },
|
|
|
|
{}
|
|
|
|
})),
|
|
|
|
QLIT_QDICT(((QLitDictEntry[]) {
|
|
|
|
{ "json-type", QLIT_QSTR("string"), },
|
|
|
|
{ "meta-type", QLIT_QSTR("builtin"), },
|
|
|
|
{ "name", QLIT_QSTR("str"), },
|
|
|
|
{}
|
|
|
|
})),
|
2022-11-04 19:06:45 +03:00
|
|
|
QLIT_QDICT(((QLitDictEntry[]) {
|
|
|
|
{ "json-type", QLIT_QSTR("boolean"), },
|
|
|
|
{ "meta-type", QLIT_QSTR("builtin"), },
|
|
|
|
{ "name", QLIT_QSTR("bool"), },
|
|
|
|
{}
|
|
|
|
})),
|
2018-08-28 15:07:36 +03:00
|
|
|
{}
|
2018-03-05 20:29:51 +03:00
|
|
|
}));
|
2018-08-28 15:07:36 +03:00
|
|
|
|
2021-07-21 02:56:17 +03:00
|
|
|
[Uninteresting stuff omitted...]
|