1.. -*- coding: utf-8; mode: rst -*-
2
3.. _func-ioctl:
4
5************
6V4L2 ioctl()
7************
8
9Name
10====
11
12v4l2-ioctl - Program a V4L2 device
13
14
15Synopsis
16========
17
18.. code-block:: c
19
20    #include <sys/ioctl.h>
21
22
23.. c:function:: int ioctl( int fd, int request, void *argp )
24    :name: v4l2-ioctl
25
26Arguments
27=========
28
29``fd``
30    File descriptor returned by :ref:`open() <func-open>`.
31
32``request``
33    V4L2 ioctl request code as defined in the ``videodev2.h`` header
34    file, for example VIDIOC_QUERYCAP.
35
36``argp``
37    Pointer to a function parameter, usually a structure.
38
39
40Description
41===========
42
43The :ref:`ioctl() <func-ioctl>` function is used to program V4L2 devices. The
44argument ``fd`` must be an open file descriptor. An ioctl ``request``
45has encoded in it whether the argument is an input, output or read/write
46parameter, and the size of the argument ``argp`` in bytes. Macros and
47defines specifying V4L2 ioctl requests are located in the
48``videodev2.h`` header file. Applications should use their own copy, not
49include the version in the kernel sources on the system they compile on.
50All V4L2 ioctl requests, their respective function and parameters are
51specified in :ref:`user-func`.
52
53
54Return Value
55============
56
57On success 0 is returned, on error -1 and the ``errno`` variable is set
58appropriately. The generic error codes are described at the
59:ref:`Generic Error Codes <gen-errors>` chapter.
60
61When an ioctl that takes an output or read/write parameter fails, the
62parameter remains unmodified.
63