[deliverable/linux.git] / Documentation / media / uapi / v4l / func-ioctl.rst

.. -*- coding: utf-8; mode: rst -*-

.. _func-ioctl:

************
V4L2 ioctl()
************

Name
====

v4l2-ioctl - Program a V4L2 device


Synopsis
========

.. code-block:: c

    #include <sys/ioctl.h>


.. c:function:: int ioctl( int fd, int request, void *argp )
    :name: v4l2-ioctl

Arguments
=========

``fd``
    File descriptor returned by :ref:`open() <func-open>`.

``request``
    V4L2 ioctl request code as defined in the ``videodev2.h`` header
    file, for example VIDIOC_QUERYCAP.

``argp``
    Pointer to a function parameter, usually a structure.


Description
===========

The :ref:`ioctl() <func-ioctl>` function is used to program V4L2 devices. The
argument ``fd`` must be an open file descriptor. An ioctl ``request``
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
defines specifying V4L2 ioctl requests are located in the
``videodev2.h`` header file. Applications should use their own copy, not
include the version in the kernel sources on the system they compile on.
All V4L2 ioctl requests, their respective function and parameters are
specified in :ref:`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.

When an ioctl that takes an output or read/write parameter fails, the
parameter remains unmodified.
Commit	Line	Data
5377d91f MH	1	.. -- coding: utf-8; mode: rst --
	2
	3	.. _func-ioctl:
	4
	5	************
	6	V4L2 ioctl()
	7	************
	8
15e7d615	9	Name
586027ce	10	====
5377d91f	11
586027ce	12	v4l2-ioctl - Program a V4L2 device
5377d91f	13
15e7d615 MCC	14
15e7d615 MCC	15	Synopsis
5377d91f MH	16	========
	17
	18	.. code-block:: c
	19
	20	#include <sys/ioctl.h>
	21
	22
1b81f010	23	.. c:function:: int ioctl( int fd, int request, void *argp )
41d80465	24	:name: v4l2-ioctl
586027ce	25
15e7d615	26	Arguments
5377d91f MH	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
15e7d615	40	Description
5377d91f MH	41	===========
5377d91f MH	42
760c7010	43	The :ref:`ioctl() <func-ioctl>` function is used to program V4L2 devices. The
5377d91f MH	44	argument ``fd`` must be an open file descriptor. An ioctl ``request``
	45	has encoded in it whether the argument is an input, output or read/write
	46	parameter, and the size of the argument ``argp`` in bytes. Macros and
	47	defines specifying V4L2 ioctl requests are located in the
	48	``videodev2.h`` header file. Applications should use their own copy, not
	49	include the version in the kernel sources on the system they compile on.
	50	All V4L2 ioctl requests, their respective function and parameters are
	51	specified in :ref:`user-func`.
	52
	53
15e7d615	54	Return Value
5377d91f MH	55	============
	56
	57	On success 0 is returned, on error -1 and the ``errno`` variable is set
	58	appropriately. The generic error codes are described at the
	59	:ref:`Generic Error Codes <gen-errors>` chapter.
	60
	61	When an ioctl that takes an output or read/write parameter fails, the
	62	parameter remains unmodified.