weston/protocol/weston-debug.xml

<?xml version="1.0" encoding="UTF-8"?>
<protocol name="weston_debug">

  <copyright>
    Copyright © 2017 Pekka Paalanen pq@iki.fi
    Copyright © 2018 Zodiac Inflight Innovations

    Permission is hereby granted, free of charge, to any person obtaining a
    copy of this software and associated documentation files (the "Software"),
    to deal in the Software without restriction, including without limitation
    the rights to use, copy, modify, merge, publish, distribute, sublicense,
    and/or sell copies of the Software, and to permit persons to whom the
    Software is furnished to do so, subject to the following conditions:

    The above copyright notice and this permission notice (including the next
    paragraph) shall be included in all copies or substantial portions of the
    Software.

    THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
    IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
    FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
    THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
    LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
    FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
    DEALINGS IN THE SOFTWARE.
  </copyright>

  <interface name="weston_debug_v1" version="1">
    <description summary="weston internal debugging">
      This is a generic debugging interface for Weston internals, the global
      object advertized through wl_registry.

      WARNING: This interface by design allows a denial-of-service attack. It
      should not be offered in production, or proper authorization mechnisms
      must be enforced.

      The idea is for a client to provide a file descriptor that the server
      uses for printing debug information. The server uses the file
      descriptor in blocking writes mode, which exposes the denial-of-service
      risk. The blocking mode is necessary to ensure all debug messages can
      be easily printed in place. It also ensures message ordering if a
      client subcribes to more than one debug stream.

      The available debugging features depend on the server.

      A debug stream can be one-shot where the server prints the requested
      information and then closes it, or continuous where server keeps on
      printing until the client stops it. Or anything in between.
    </description>

    <request name="destroy" type="destructor">
      <description summary="destroy factory object">
	Destroys the factory object, but does not affect any other objects.
      </description>
    </request>

    <event name="available">
      <description summary="advertise available debug scope">
        Advertises an available debug scope which the client may be able to
        bind to. No information is provided by the server about the content
        contained within the debug streams provided by the scope, once a
        client has subscribed.
      </description>

      <arg name="name" type="string" allow-null="false"
           summary="debug stream name"/>
      <arg name="description" type="string" allow-null="true"
           summary="human-readable description of the debug scope"/>
    </event>

    <request name="subscribe">
      <description summary="subscribe to a debug stream">
	Subscribe to a named debug stream. The server will start printing
	to the given file descriptor.

	If the named debug stream is a one-shot dump, the server will send
	weston_debug_stream_v1.complete event once all requested data has
	been printed. Otherwise, the server will continue streaming debug
	prints until the subscription object is destroyed.

	If the debug stream name is unknown to the server, the server will
	immediately respond with weston_debug_stream_v1.failure event.
      </description>

      <arg name="name" type="string" allow-null="false"
           summary="debug stream name"/>
      <arg name="streamfd" type="fd" summary="write stream file descriptor"/>
      <arg name="stream" type="new_id" interface="weston_debug_stream_v1"
           summary="created debug stream object"/>
    </request>
  </interface>

  <interface name="weston_debug_stream_v1" version="1">
    <description summary="A subscribed debug stream">
      Represents one subscribed debug stream, created with
      weston_debug_v1.subscribe. When the object is created, it is associated
      with a given file descriptor. The server will continue writing to the
      file descriptor until the object is destroyed or the server sends an
      event through the object.
    </description>

    <request name="destroy" type="destructor">
      <description summary="close a debug stream">
	Destroys the object, which causes the server to stop writing into
	and closes the associated file descriptor if it was not closed
	already.

	Use a wl_display.sync if the clients needs to guarantee the file
	descriptor is closed before continuing.
      </description>
    </request>

    <event name="complete">
      <description summary="server completed the debug stream">
	The server has successfully finished writing to and has closed the
	associated file descriptor.

	This event is delivered only for one-shot debug streams where the
	server dumps some data and stop. This is never delivered for
	continuous debbug streams because they by definition never complete.
      </description>
    </event>

    <event name="failure">
      <description summary="server cannot continue the debug stream">
	The server has stopped writing to and has closed the
	associated file descriptor. The data already written to the file
	descriptor is correct, but it may be truncated.

	This event may be delivered at any time and for any kind of debug
	stream. It may be due to a failure in or shutdown of the server.
	The message argument may provide a hint of the reason.
      </description>

      <arg name="message" type="string" allow-null="true"
           summary="human readable reason"/>
    </event>
  </interface>
</protocol>