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.. _VIDIOC_G_OUTPUT:
11
12**************************************
13ioctl VIDIOC_G_OUTPUT, VIDIOC_S_OUTPUT
14**************************************
15
16Name
17====
18
19VIDIOC_G_OUTPUT - VIDIOC_S_OUTPUT - Query or select the current video output
20
21
22Synopsis
23========
24
25.. c:function:: int ioctl( int fd, VIDIOC_G_OUTPUT, int *argp )
26    :name: VIDIOC_G_OUTPUT
27
28.. c:function:: int ioctl( int fd, VIDIOC_S_OUTPUT, int *argp )
29    :name: VIDIOC_S_OUTPUT
30
31
32Arguments
33=========
34
35``fd``
36    File descriptor returned by :ref:`open() <func-open>`.
37
38``argp``
39    Pointer to an integer with output index.
40
41
42Description
43===========
44
45To query the current video output applications call the
46:ref:`VIDIOC_G_OUTPUT <VIDIOC_G_OUTPUT>` ioctl with a pointer to an integer where the driver
47stores the number of the output, as in the struct
48:c:type:`v4l2_output` ``index`` field. This ioctl will
49fail only when there are no video outputs, returning the ``EINVAL`` error
50code.
51
52To select a video output applications store the number of the desired
53output in an integer and call the :ref:`VIDIOC_S_OUTPUT <VIDIOC_G_OUTPUT>` ioctl with a
54pointer to this integer. Side effects are possible. For example outputs
55may support different video standards, so the driver may implicitly
56switch the current standard. standard. Because of these possible side
57effects applications must select an output before querying or
58negotiating any other parameters.
59
60Information about video outputs is available using the
61:ref:`VIDIOC_ENUMOUTPUT` ioctl.
62
63
64Return Value
65============
66
67On success 0 is returned, on error -1 and the ``errno`` variable is set
68appropriately. The generic error codes are described at the
69:ref:`Generic Error Codes <gen-errors>` chapter.
70
71EINVAL
72    The number of the video output is out of bounds, or there are no
73    video outputs at all.
74