1.. Permission is granted to copy, distribute and/or modify this 2.. document under the terms of the GNU Free Documentation License, 3.. Version 1.1 or any later version published by the Free Software 4.. Foundation, with no Invariant Sections, no Front-Cover Texts 5.. and no Back-Cover Texts. A copy of the license is included at 6.. Documentation/userspace-api/media/fdl-appendix.rst. 7.. 8.. TODO: replace it to GFDL-1.1-or-later WITH no-invariant-sections 9 10.. _func-ioctl: 11 12************ 13V4L2 ioctl() 14************ 15 16Name 17==== 18 19v4l2-ioctl - Program a V4L2 device 20 21 22Synopsis 23======== 24 25.. code-block:: c 26 27 #include <sys/ioctl.h> 28 29 30.. c:function:: int ioctl( int fd, int request, void *argp ) 31 :name: v4l2-ioctl 32 33Arguments 34========= 35 36``fd`` 37 File descriptor returned by :ref:`open() <func-open>`. 38 39``request`` 40 V4L2 ioctl request code as defined in the ``videodev2.h`` header 41 file, for example VIDIOC_QUERYCAP. 42 43``argp`` 44 Pointer to a function parameter, usually a structure. 45 46 47Description 48=========== 49 50The :ref:`ioctl() <func-ioctl>` function is used to program V4L2 devices. The 51argument ``fd`` must be an open file descriptor. An ioctl ``request`` 52has encoded in it whether the argument is an input, output or read/write 53parameter, and the size of the argument ``argp`` in bytes. Macros and 54defines specifying V4L2 ioctl requests are located in the 55``videodev2.h`` header file. Applications should use their own copy, not 56include the version in the kernel sources on the system they compile on. 57All V4L2 ioctl requests, their respective function and parameters are 58specified in :ref:`user-func`. 59 60 61Return Value 62============ 63 64On success 0 is returned, on error -1 and the ``errno`` variable is set 65appropriately. The generic error codes are described at the 66:ref:`Generic Error Codes <gen-errors>` chapter. 67 68When an ioctl that takes an output or read/write parameter fails, the 69parameter remains unmodified. 70