tjh.dev
Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
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>__u32</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 type must be set
102to <constant>V4L2_TUNER_RADIO</constant> for <filename>/dev/radioX</filename>
103device nodes, and to <constant>V4L2_TUNER_ANALOG_TV</constant>
104for all others. Set this field to <constant>V4L2_TUNER_RADIO</constant> for
105modulators (currently only radio modulators are supported).
106See <xref linkend="v4l2-tuner-type" /></entry>
107 </row>
108 <row>
109 <entry>__u32</entry>
110 <entry><structfield>frequency</structfield></entry>
111 <entry>Tuning frequency in units of 62.5 kHz, or if the
112&v4l2-tuner; or &v4l2-modulator; <structfield>capabilities</structfield> flag
113<constant>V4L2_TUNER_CAP_LOW</constant> is set, in units of 62.5
114Hz.</entry>
115 </row>
116 <row>
117 <entry>__u32</entry>
118 <entry><structfield>reserved</structfield>[8]</entry>
119 <entry>Reserved for future extensions. Drivers and
120 applications must set the array to zero.</entry>
121 </row>
122 </tbody>
123 </tgroup>
124 </table>
125 </refsect1>
126
127 <refsect1>
128 &return-value;
129
130 <variablelist>
131 <varlistentry>
132 <term><errorcode>EINVAL</errorcode></term>
133 <listitem>
134 <para>The <structfield>tuner</structfield> index is out of
135bounds or the value in the <structfield>type</structfield> field is
136wrong.</para>
137 </listitem>
138 </varlistentry>
139 <varlistentry>
140 <term><errorcode>EBUSY</errorcode></term>
141 <listitem>
142 <para>A hardware seek is in progress.</para>
143 </listitem>
144 </varlistentry>
145 </variablelist>
146 </refsect1>
147</refentry>