1 .. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later 2 .. c:namespace:: V4L 3 4 .. _func-ioctl: 5 6 ************ 7 V4L2 ioctl() 8 ************ 9 10 Name 11 ==== 12 13 v4l2-ioctl - Program a V4L2 device 14 15 Synopsis 16 ======== 17 18 .. code-block:: c 19 20 #include <sys/ioctl.h> 21 22 ``int ioctl(int fd, int request, void *argp)`` 23 24 Arguments 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 37 Description 38 =========== 39 40 The :ref:`ioctl() <func-ioctl>` function is used to program V4L2 devices. The 41 argument ``fd`` must be an open file descriptor. An ioctl ``request`` 42 has encoded in it whether the argument is an input, output or read/write 43 parameter, and the size of the argument ``argp`` in bytes. Macros and 44 defines specifying V4L2 ioctl requests are located in the 45 ``videodev2.h`` header file. Applications should use their own copy, not 46 include the version in the kernel sources on the system they compile on. 47 All V4L2 ioctl requests, their respective function and parameters are 48 specified in :ref:`user-func`. 49 50 Return Value 51 ============ 52 53 On success 0 is returned, on error -1 and the ``errno`` variable is set 54 appropriately. The generic error codes are described at the 55 :ref:`Generic Error Codes <gen-errors>` chapter. 56 57 When an ioctl that takes an output or read/write parameter fails, the 58 parameter remains unmodified.
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