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