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.. SPDX-License-Identifier: GPL-2.0 OR GFDL-1.1-no-invariants-or-later
.. _request-func-ioctl:
***************
request ioctl()
***************
Name
====
request-ioctl - Control a request file descriptor
Synopsis
========
.. code-block:: c
#include <sys/ioctl.h>
.. c:function:: int ioctl( int fd, int cmd, void *argp )
:name: req-ioctl
Arguments
=========
``fd``
File descriptor returned by :ref:`MEDIA_IOC_REQUEST_ALLOC`.
``cmd``
The request ioctl command code as defined in the media.h header file, for
example :ref:`MEDIA_REQUEST_IOC_QUEUE`.
``argp``
Pointer to a request-specific structure.
Description
===========
The :ref:`ioctl() <request-func-ioctl>` function manipulates request
parameters. The argument ``fd`` must be an open file descriptor.
The ioctl ``cmd`` code specifies the request function to be called. It
has encoded in it whether the argument is an input, output or read/write
parameter, and the size of the argument ``argp`` in bytes.
Macros and structures definitions specifying request ioctl commands and
their parameters are located in the media.h header file. All request ioctl
commands, their respective function and parameters are specified in
:ref:`media-user-func`.
Return Value
============
On success 0 is returned, on error -1 and the ``errno`` variable is set
appropriately. The generic error codes are described at the
:ref:`Generic Error Codes <gen-errors>` chapter.
Command-specific error codes are listed in the individual command
descriptions.
When an ioctl that takes an output or read/write parameter fails, the
parameter remains unmodified.
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