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1.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later2.. c:namespace:: V4L3 4.. _func-ioctl:5 6************7V4L2 ioctl()8************9 10Name11====12 13v4l2-ioctl - Program a V4L2 device14 15Synopsis16========17 18.. code-block:: c19 20 #include <sys/ioctl.h>21 22``int ioctl(int fd, int request, void *argp)``23 24Arguments25=========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`` header32 file, for example VIDIOC_QUERYCAP.33 34``argp``35 Pointer to a function parameter, usually a structure.36 37Description38===========39 40The :ref:`ioctl() <func-ioctl>` function is used to program V4L2 devices. The41argument ``fd`` must be an open file descriptor. An ioctl ``request``42has encoded in it whether the argument is an input, output or read/write43parameter, and the size of the argument ``argp`` in bytes. Macros and44defines specifying V4L2 ioctl requests are located in the45``videodev2.h`` header file. Applications should use their own copy, not46include the version in the kernel sources on the system they compile on.47All V4L2 ioctl requests, their respective function and parameters are48specified in :ref:`user-func`.49 50Return Value51============52 53On success 0 is returned, on error -1 and the ``errno`` variable is set54appropriately. The generic error codes are described at the55:ref:`Generic Error Codes <gen-errors>` chapter.56 57When an ioctl that takes an output or read/write parameter fails, the58parameter remains unmodified.59