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.. -*- coding: utf-8; mode: rst -*-
.. _media-func-ioctl:
*************
media ioctl()
*************
Name
====
media-ioctl - Control a media device
Synopsis
========
.. code-block:: c
#include <sys/ioctl.h>
.. cpp:function:: int ioctl( int fd, int request, void *argp )
Arguments
=========
``fd``
File descriptor returned by :ref:`open() <func-open>`.
``request``
Media ioctl request code as defined in the media.h header file, for
example MEDIA_IOC_SETUP_LINK.
``argp``
Pointer to a request-specific structure.
Description
===========
The :ref:`ioctl() <media-func-ioctl>` function manipulates media device
parameters. The argument ``fd`` must be an open file descriptor.
The ioctl ``request`` code specifies the media 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 media ioctl requests and
their parameters are located in the media.h header file. All media ioctl
requests, 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.
Request-specific error codes are listed in the individual requests
descriptions.
When an ioctl that takes an output or read/write parameter fails, the
parameter remains unmodified.
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