1<refentry id="vidioc-g-output">
2  <refmeta>
3    <refentrytitle>ioctl VIDIOC_G_OUTPUT, VIDIOC_S_OUTPUT</refentrytitle>
4    &manvol;
5  </refmeta>
6
7  <refnamediv>
8    <refname>VIDIOC_G_OUTPUT</refname>
9    <refname>VIDIOC_S_OUTPUT</refname>
10    <refpurpose>Query or select the current video output</refpurpose>
11  </refnamediv>
12
13  <refsynopsisdiv>
14    <funcsynopsis>
15      <funcprototype>
16	<funcdef>int <function>ioctl</function></funcdef>
17	<paramdef>int <parameter>fd</parameter></paramdef>
18	<paramdef>int <parameter>request</parameter></paramdef>
19	<paramdef>int *<parameter>argp</parameter></paramdef>
20      </funcprototype>
21    </funcsynopsis>
22  </refsynopsisdiv>
23
24  <refsect1>
25    <title>Arguments</title>
26
27    <variablelist>
28      <varlistentry>
29	<term><parameter>fd</parameter></term>
30	<listitem>
31	  <para>&fd;</para>
32	</listitem>
33      </varlistentry>
34      <varlistentry>
35	<term><parameter>request</parameter></term>
36	<listitem>
37	  <para>VIDIOC_G_OUTPUT, VIDIOC_S_OUTPUT</para>
38	</listitem>
39      </varlistentry>
40      <varlistentry>
41	<term><parameter>argp</parameter></term>
42	<listitem>
43	  <para></para>
44	</listitem>
45      </varlistentry>
46    </variablelist>
47  </refsect1>
48
49  <refsect1>
50    <title>Description</title>
51
52    <para>To query the current video output applications call the
53<constant>VIDIOC_G_OUTPUT</constant> ioctl with a pointer to an integer
54where the driver stores the number of the output, as in the
55&v4l2-output; <structfield>index</structfield> field. This ioctl
56will fail only when there are no video outputs, returning the
57&EINVAL;.</para>
58
59    <para>To select a video output applications store the number of the
60desired output in an integer and call the
61<constant>VIDIOC_S_OUTPUT</constant> ioctl with a pointer to this integer.
62Side effects are possible. For example outputs may support different
63video standards, so the driver may implicitly switch the current
64standard.
65standard. Because of these possible side effects applications
66must select an output before querying or negotiating any other parameters.</para>
67
68    <para>Information about video outputs is available using the
69&VIDIOC-ENUMOUTPUT; ioctl.</para>
70  </refsect1>
71
72  <refsect1>
73    &return-value;
74
75    <variablelist>
76      <varlistentry>
77	<term><errorcode>EINVAL</errorcode></term>
78	<listitem>
79	  <para>The number of the video output is out of bounds, or
80there are no video outputs at all.</para>
81	</listitem>
82      </varlistentry>
83    </variablelist>
84  </refsect1>
85</refentry>
86