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authorMauro Carvalho Chehab <mchehab@redhat.com>2009-09-13 21:16:04 -0400
committerMauro Carvalho Chehab <mchehab@redhat.com>2009-09-18 22:47:55 -0400
commit8e080c2e6cadada82a6b520e0c23a1cb974822d5 (patch)
tree991450ff1abba98e5313906478c33816a202ccab /Documentation/DocBook/v4l/vidioc-g-frequency.xml
parentf4e96deb4513d044653027d4921fd7592195503a (diff)
V4L/DVB (12761): DocBook: add media API specs
The V4L and DVB API's are there for a long time. however, up to now, no efforts were done to merge them to kernel DocBook. This patch adds the current versions of the specs as an unique compendium. Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
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1<refentry id="vidioc-g-frequency">
2 <refmeta>
3 <refentrytitle>ioctl VIDIOC_G_FREQUENCY, VIDIOC_S_FREQUENCY</refentrytitle>
4 &manvol;
5 </refmeta>
6
7 <refnamediv>
8 <refname>VIDIOC_G_FREQUENCY</refname>
9 <refname>VIDIOC_S_FREQUENCY</refname>
10 <refpurpose>Get or set tuner or modulator radio
11frequency</refpurpose>
12 </refnamediv>
13
14 <refsynopsisdiv>
15 <funcsynopsis>
16 <funcprototype>
17 <funcdef>int <function>ioctl</function></funcdef>
18 <paramdef>int <parameter>fd</parameter></paramdef>
19 <paramdef>int <parameter>request</parameter></paramdef>
20 <paramdef>struct v4l2_frequency
21*<parameter>argp</parameter></paramdef>
22 </funcprototype>
23 </funcsynopsis>
24 <funcsynopsis>
25 <funcprototype>
26 <funcdef>int <function>ioctl</function></funcdef>
27 <paramdef>int <parameter>fd</parameter></paramdef>
28 <paramdef>int <parameter>request</parameter></paramdef>
29 <paramdef>const struct v4l2_frequency
30*<parameter>argp</parameter></paramdef>
31 </funcprototype>
32 </funcsynopsis>
33 </refsynopsisdiv>
34
35 <refsect1>
36 <title>Arguments</title>
37
38 <variablelist>
39 <varlistentry>
40 <term><parameter>fd</parameter></term>
41 <listitem>
42 <para>&fd;</para>
43 </listitem>
44 </varlistentry>
45 <varlistentry>
46 <term><parameter>request</parameter></term>
47 <listitem>
48 <para>VIDIOC_G_FREQUENCY, VIDIOC_S_FREQUENCY</para>
49 </listitem>
50 </varlistentry>
51 <varlistentry>
52 <term><parameter>argp</parameter></term>
53 <listitem>
54 <para></para>
55 </listitem>
56 </varlistentry>
57 </variablelist>
58 </refsect1>
59
60 <refsect1>
61 <title>Description</title>
62
63 <para>To get the current tuner or modulator radio frequency
64applications set the <structfield>tuner</structfield> field of a
65&v4l2-frequency; to the respective tuner or modulator number (only
66input devices have tuners, only output devices have modulators), zero
67out the <structfield>reserved</structfield> array and
68call the <constant>VIDIOC_G_FREQUENCY</constant> ioctl with a pointer
69to this structure. The driver stores the current frequency in the
70<structfield>frequency</structfield> field.</para>
71
72 <para>To change the current tuner or modulator radio frequency
73applications initialize the <structfield>tuner</structfield>,
74<structfield>type</structfield> and
75<structfield>frequency</structfield> fields, and the
76<structfield>reserved</structfield> array of a &v4l2-frequency; and
77call the <constant>VIDIOC_S_FREQUENCY</constant> ioctl with a pointer
78to this structure. When the requested frequency is not possible the
79driver assumes the closest possible value. However
80<constant>VIDIOC_S_FREQUENCY</constant> is a write-only ioctl, it does
81not return the actual new frequency.</para>
82
83 <table pgwide="1" frame="none" id="v4l2-frequency">
84 <title>struct <structname>v4l2_frequency</structname></title>
85 <tgroup cols="3">
86 &cs-str;
87 <tbody valign="top">
88 <row>
89 <entry>__u32</entry>
90 <entry><structfield>tuner</structfield></entry>
91 <entry>The tuner or modulator index number. This is the
92same value as in the &v4l2-input; <structfield>tuner</structfield>
93field and the &v4l2-tuner; <structfield>index</structfield> field, or
94the &v4l2-output; <structfield>modulator</structfield> field and the
95&v4l2-modulator; <structfield>index</structfield> field.</entry>
96 </row>
97 <row>
98 <entry>&v4l2-tuner-type;</entry>
99 <entry><structfield>type</structfield></entry>
100 <entry>The tuner type. This is the same value as in the
101&v4l2-tuner; <structfield>type</structfield> field. The field is not
102applicable to modulators, &ie; ignored by drivers.</entry>
103 </row>
104 <row>
105 <entry>__u32</entry>
106 <entry><structfield>frequency</structfield></entry>
107 <entry>Tuning frequency in units of 62.5 kHz, or if the
108&v4l2-tuner; or &v4l2-modulator; <structfield>capabilities</structfield> flag
109<constant>V4L2_TUNER_CAP_LOW</constant> is set, in units of 62.5
110Hz.</entry>
111 </row>
112 <row>
113 <entry>__u32</entry>
114 <entry><structfield>reserved</structfield>[8]</entry>
115 <entry>Reserved for future extensions. Drivers and
116 applications must set the array to zero.</entry>
117 </row>
118 </tbody>
119 </tgroup>
120 </table>
121 </refsect1>
122
123 <refsect1>
124 &return-value;
125
126 <variablelist>
127 <varlistentry>
128 <term><errorcode>EINVAL</errorcode></term>
129 <listitem>
130 <para>The <structfield>tuner</structfield> index is out of
131bounds or the value in the <structfield>type</structfield> field is
132wrong.</para>
133 </listitem>
134 </varlistentry>
135 </variablelist>
136 </refsect1>
137</refentry>
138
139<!--
140Local Variables:
141mode: sgml
142sgml-parent-document: "v4l2.sgml"
143indent-tabs-mode: nil
144End:
145-->