mirror of https://github.com/dzavalishin/openpod
example
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Dmitry Zavalishin
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@ -2,5 +2,111 @@
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Simplest driver skeleton
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========================
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lets review a simplest driver example provided in project repository.
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Please see ``barebones/simple`` directory for this example's source code.
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-----------------
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Driver descriptor
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-----------------
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First we need to provide driver descriptor structure.
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.. code:: c
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pod_driver simple_driver = {
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POD_DRIVER_MAGIC,
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POD_DRIVER_VERSION,
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POD_DRIVER_ARCH_UNKNOWN,
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POD_DEV_CLASS_VIDEO, 0, 0, 0,
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"simple driver skeleton - RENAME ME!",
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{
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simple_driver_construct,
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simple_driver_destruct,
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simple_driver_activate,
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simple_driver_deactivate,
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simple_driver_sense
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},
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0, // no optional entry points
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0, // no properties
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0, // Private state does not exist yet
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0, // Statically linked, no need for kernel entry points struct
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};
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The only notable things here are:
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* ``POD_DEV_CLASS_VIDEO`` - we declare that this is a video driver. OS might decide to start different
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drivers sooner or later, or to group drivers start by classes.
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* ``simple_driver_X`` - entry points to start and stop our driver by OS.
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-----------------
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Device descriptor
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-----------------
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Our driver will provide just one and only device, so device descriptor
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can be static too.
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.. code:: c
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pod_device simple_device =
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{
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POD_DEVICE_MAGIC, // magic
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POD_DEV_CLASS_VIDEO,
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0, 0,
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0, // flags
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// Device name, either static or runtime-generated
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"simple driver skeleton device name - RENAME ME!",
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&simple_driver,
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&dev_func, // dev io entry points
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0, // no properties
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0, // dev class specific interface
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0, // private data
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0, // default request q
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0, // request we do now
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0, // thread used to run requests
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0, // triggered to run next request
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};
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Again, we note that dev class is ``POD_DEV_CLASS_VIDEO``. It is critical to be
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correct - OS will connect device to its users based on this.
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We provide device entry points for async interface, but all of them are default
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ones provided by OpenPOD library.
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.. code:: c
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static pod_dev_f dev_func =
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{
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pod_default_enqueue,
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pod_default_dequeue,
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pod_default_fence,
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pod_default_raise
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};
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First of them, ``pod_default_enqueue``, will just call syncronous entry point of driver,
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three other are no-ops.
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@ -30,11 +30,16 @@ Source codes for the project (and for this book) can be found in `OpenPOD GitHub
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.. _PDF format: https://buildmedia.readthedocs.org/media/pdf/phantomdox/latest/phantomdox.pdf
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.........
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Rationale
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.........
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.. include:: introduction.rst.inc
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.................
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Project structure
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.................
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..................
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Project navigation
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..................
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.. include:: directories.rst.inc
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@ -36,4 +36,4 @@ Goal is to define API and driver structure that is:
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Current state of specification: It is partially complete and waits for your comments.
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The best way to comment is to create an issue in project's GitHub repository: <https://github.com/dzavalishin/openpod/issues>.
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The best way to comment is to create an issue in project's `GitHub repository: <https://github.com/dzavalishin/openpod/issues>`_.
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@ -5,12 +5,13 @@ OpenPOD driver includes:
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Driver descriptor is a required part of a driver.
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* **Device descriptor.** A structure which describes each device exported by driver. Can be single and
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static, or can be dynamically allocated in run time. For example, USB disk driver can create device
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descriptors dynamically as devices come and go.
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Device descriptor is not a required part - there can be driver which does not export devices at all
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or just starts with empty set of devices. But most drivers will provide at least one device at start.
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* **Device descriptor.** A structure which describes each device exported by driver. Can be single and
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static, or can be dynamically allocated in run time. For example, USB disk driver can create device
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descriptors dynamically as devices come and go.
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Device descriptor is not a required part - there can be driver which does not export devices at all
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or just starts with empty set of devices. But most drivers will provide at least one device at start.
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* **Driver and/or device properties.** Set of key=value parameters to control driver or device and
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request meta information. For example, sound driver can set sampling rate with corresponding
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