1.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
2.. c:namespace:: V4L
3
4.. _func-ioctl:
5
6************
7V4L2 ioctl()
8************
9
10Name
11====
12
13v4l2-ioctl - Program a V4L2 device
14
15Synopsis
16========
17
18.. code-block:: c
19
20    #include <sys/ioctl.h>
21
22``int ioctl(int fd, int request, void *argp)``
23
24Arguments
25=========
26
27``fd``
28    File descriptor returned by :c:func:`open()`.
29
30``request``
31    V4L2 ioctl request code as defined in the ``videodev2.h`` header
32    file, for example VIDIOC_QUERYCAP.
33
34``argp``
35    Pointer to a function parameter, usually a structure.
36
37Description
38===========
39
40The :ref:`ioctl() <func-ioctl>` function is used to program V4L2 devices. The
41argument ``fd`` must be an open file descriptor. An ioctl ``request``
42has encoded in it whether the argument is an input, output or read/write
43parameter, and the size of the argument ``argp`` in bytes. Macros and
44defines specifying V4L2 ioctl requests are located in the
45``videodev2.h`` header file. Applications should use their own copy, not
46include the version in the kernel sources on the system they compile on.
47All V4L2 ioctl requests, their respective function and parameters are
48specified in :ref:`user-func`.
49
50Return Value
51============
52
53On success 0 is returned, on error -1 and the ``errno`` variable is set
54appropriately. The generic error codes are described at the
55:ref:`Generic Error Codes <gen-errors>` chapter.
56
57When an ioctl that takes an output or read/write parameter fails, the
58parameter remains unmodified.
59