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 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. The field is not applicable to modulators, &ie; ignored
105by drivers.</entry>
106	  </row>
107	  <row>
108	    <entry>__u32</entry>
109	    <entry><structfield>frequency</structfield></entry>
110	    <entry>Tuning frequency in units of 62.5 kHz, or if the
111&v4l2-tuner; or &v4l2-modulator; <structfield>capabilities</structfield> flag
112<constant>V4L2_TUNER_CAP_LOW</constant> is set, in units of 62.5
113Hz.</entry>
114	  </row>
115	  <row>
116	    <entry>__u32</entry>
117	    <entry><structfield>reserved</structfield>[8]</entry>
118	    <entry>Reserved for future extensions. Drivers and
119	    applications must set the array to zero.</entry>
120	  </row>
121	</tbody>
122      </tgroup>
123    </table>
124  </refsect1>
125
126  <refsect1>
127    &return-value;
128
129    <variablelist>
130      <varlistentry>
131	<term><errorcode>EINVAL</errorcode></term>
132	<listitem>
133	  <para>The <structfield>tuner</structfield> index is out of
134bounds or the value in the <structfield>type</structfield> field is
135wrong.</para>
136	</listitem>
137      </varlistentry>
138    </variablelist>
139  </refsect1>
140</refentry>
141