1.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
2.. c:namespace:: V4L
3
4.. _VIDIOC_G_OUTPUT:
5
6**************************************
7ioctl VIDIOC_G_OUTPUT, VIDIOC_S_OUTPUT
8**************************************
9
10Name
11====
12
13VIDIOC_G_OUTPUT - VIDIOC_S_OUTPUT - Query or select the current video output
14
15Synopsis
16========
17
18.. c:macro:: VIDIOC_G_OUTPUT
19
20``int ioctl(int fd, VIDIOC_G_OUTPUT, int *argp)``
21
22.. c:macro:: VIDIOC_S_OUTPUT
23
24``int ioctl(int fd, VIDIOC_S_OUTPUT, int *argp)``
25
26Arguments
27=========
28
29``fd``
30    File descriptor returned by :c:func:`open()`.
31
32``argp``
33    Pointer to an integer with output index.
34
35Description
36===========
37
38To query the current video output applications call the
39:ref:`VIDIOC_G_OUTPUT <VIDIOC_G_OUTPUT>` ioctl with a pointer to an integer where the driver
40stores the number of the output, as in the struct
41:c:type:`v4l2_output` ``index`` field. This ioctl will
42fail only when there are no video outputs, returning the ``EINVAL`` error
43code.
44
45To select a video output applications store the number of the desired
46output in an integer and call the :ref:`VIDIOC_S_OUTPUT <VIDIOC_G_OUTPUT>` ioctl with a
47pointer to this integer. Side effects are possible. For example outputs
48may support different video standards, so the driver may implicitly
49switch the current standard. Because of these possible side
50effects applications must select an output before querying or
51negotiating any other parameters.
52
53Information about video outputs is available using the
54:ref:`VIDIOC_ENUMOUTPUT` ioctl.
55
56Return Value
57============
58
59On success 0 is returned, on error -1 and the ``errno`` variable is set
60appropriately. The generic error codes are described at the
61:ref:`Generic Error Codes <gen-errors>` chapter.
62
63EINVAL
64    The number of the video output is out of bounds, or there are no
65    video outputs at all.
66