68 lines
1.6 KiB
ReStructuredText
68 lines
1.6 KiB
ReStructuredText
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.. SPDX-License-Identifier: GPL-2.0 OR GFDL-1.1-or-later WITH no-invariant-sections
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.. _request-func-ioctl:
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***************
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request ioctl()
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***************
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Name
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====
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request-ioctl - Control a request file descriptor
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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 cmd, void *argp )
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:name: req-ioctl
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Arguments
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=========
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``fd``
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File descriptor returned by :ref:`MEDIA_IOC_REQUEST_ALLOC`.
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``cmd``
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The request ioctl command code as defined in the media.h header file, for
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example :ref:`MEDIA_REQUEST_IOC_QUEUE`.
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``argp``
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Pointer to a request-specific structure.
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Description
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===========
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The :ref:`ioctl() <request-func-ioctl>` function manipulates request
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parameters. The argument ``fd`` must be an open file descriptor.
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The ioctl ``cmd`` code specifies the request function to be called. It
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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.
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Macros and structures definitions specifying request ioctl commands and
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their parameters are located in the media.h header file. All request ioctl
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commands, their respective function and parameters are specified in
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:ref:`media-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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Command-specific error codes are listed in the individual command
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descriptions.
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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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