summaryrefslogtreecommitdiff
path: root/Documentation/media/uapi/mediactl/request-func-ioctl.rst
blob: ff7b072a69991970aba4e3ea35c897bc10f0f4b4 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
.. SPDX-License-Identifier: GPL-2.0 OR GFDL-1.1-or-later WITH no-invariant-sections

.. _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.