63 строки
1.5 KiB
ReStructuredText
63 строки
1.5 KiB
ReStructuredText
.. -*- coding: utf-8; mode: rst -*-
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.. _func-ioctl:
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************
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V4L2 ioctl()
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************
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Name
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====
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v4l2-ioctl - Program a V4L2 device
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Synopsis
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========
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.. code-block:: c
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#include <sys/ioctl.h>
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.. c:function:: int ioctl( int fd, int request, void *argp )
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:name: v4l2-ioctl
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Arguments
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=========
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``fd``
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File descriptor returned by :ref:`open() <func-open>`.
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``request``
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V4L2 ioctl request code as defined in the ``videodev2.h`` header
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file, for example VIDIOC_QUERYCAP.
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``argp``
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Pointer to a function parameter, usually a structure.
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Description
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===========
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The :ref:`ioctl() <func-ioctl>` function is used to program V4L2 devices. The
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argument ``fd`` must be an open file descriptor. An ioctl ``request``
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has encoded in it whether the argument is an input, output or read/write
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parameter, and the size of the argument ``argp`` in bytes. Macros and
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defines specifying V4L2 ioctl requests are located in the
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``videodev2.h`` header file. Applications should use their own copy, not
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include the version in the kernel sources on the system they compile on.
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All V4L2 ioctl requests, their respective function and parameters are
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specified in :ref:`user-func`.
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Return Value
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============
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On success 0 is returned, on error -1 and the ``errno`` variable is set
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appropriately. The generic error codes are described at the
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:ref:`Generic Error Codes <gen-errors>` chapter.
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When an ioctl that takes an output or read/write parameter fails, the
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parameter remains unmodified.
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