1 .. SPDX-License-Identifier: GFDL-1.1-no-invari 1 .. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
2 .. c:namespace:: V4L 2 .. c:namespace:: V4L
3 3
4 .. _func-ioctl: 4 .. _func-ioctl:
5 5
6 ************ 6 ************
7 V4L2 ioctl() 7 V4L2 ioctl()
8 ************ 8 ************
9 9
10 Name 10 Name
11 ==== 11 ====
12 12
13 v4l2-ioctl - Program a V4L2 device 13 v4l2-ioctl - Program a V4L2 device
14 14
15 Synopsis 15 Synopsis
16 ======== 16 ========
17 17
18 .. code-block:: c 18 .. code-block:: c
19 19
20 #include <sys/ioctl.h> 20 #include <sys/ioctl.h>
21 21
22 ``int ioctl(int fd, int request, void *argp)`` 22 ``int ioctl(int fd, int request, void *argp)``
23 23
24 Arguments 24 Arguments
25 ========= 25 =========
26 26
27 ``fd`` 27 ``fd``
28 File descriptor returned by :c:func:`open( 28 File descriptor returned by :c:func:`open()`.
29 29
30 ``request`` 30 ``request``
31 V4L2 ioctl request code as defined in the 31 V4L2 ioctl request code as defined in the ``videodev2.h`` header
32 file, for example VIDIOC_QUERYCAP. 32 file, for example VIDIOC_QUERYCAP.
33 33
34 ``argp`` 34 ``argp``
35 Pointer to a function parameter, usually a 35 Pointer to a function parameter, usually a structure.
36 36
37 Description 37 Description
38 =========== 38 ===========
39 39
40 The :ref:`ioctl() <func-ioctl>` function is us 40 The :ref:`ioctl() <func-ioctl>` function is used to program V4L2 devices. The
41 argument ``fd`` must be an open file descripto 41 argument ``fd`` must be an open file descriptor. An ioctl ``request``
42 has encoded in it whether the argument is an i 42 has encoded in it whether the argument is an input, output or read/write
43 parameter, and the size of the argument ``argp 43 parameter, and the size of the argument ``argp`` in bytes. Macros and
44 defines specifying V4L2 ioctl requests are loc 44 defines specifying V4L2 ioctl requests are located in the
45 ``videodev2.h`` header file. Applications shou 45 ``videodev2.h`` header file. Applications should use their own copy, not
46 include the version in the kernel sources on t 46 include the version in the kernel sources on the system they compile on.
47 All V4L2 ioctl requests, their respective func 47 All V4L2 ioctl requests, their respective function and parameters are
48 specified in :ref:`user-func`. 48 specified in :ref:`user-func`.
49 49
50 Return Value 50 Return Value
51 ============ 51 ============
52 52
53 On success 0 is returned, on error -1 and the 53 On success 0 is returned, on error -1 and the ``errno`` variable is set
54 appropriately. The generic error codes are des 54 appropriately. The generic error codes are described at the
55 :ref:`Generic Error Codes <gen-errors>` chapte 55 :ref:`Generic Error Codes <gen-errors>` chapter.
56 56
57 When an ioctl that takes an output or read/wri 57 When an ioctl that takes an output or read/write parameter fails, the
58 parameter remains unmodified. 58 parameter remains unmodified.
Linux® is a registered trademark of Linus Torvalds in the United States and other countries.
TOMOYO® is a registered trademark of NTT DATA CORPORATION.