59 lines
1.5 KiB
ReStructuredText
59 lines
1.5 KiB
ReStructuredText
.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
|
|
.. c:namespace:: V4L
|
|
|
|
.. _func-ioctl:
|
|
|
|
************
|
|
V4L2 ioctl()
|
|
************
|
|
|
|
Name
|
|
====
|
|
|
|
v4l2-ioctl - Program a V4L2 device
|
|
|
|
Synopsis
|
|
========
|
|
|
|
.. code-block:: c
|
|
|
|
#include <sys/ioctl.h>
|
|
|
|
``int ioctl(int fd, int request, void *argp)``
|
|
|
|
Arguments
|
|
=========
|
|
|
|
``fd``
|
|
File descriptor returned by :c: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.
|