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Based on kernel version 3.16. Page generated on 2014-08-06 21:39 EST.

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
11	frequency</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
64	applications set the <structfield>tuner</structfield> field of a
65	&v4l2-frequency; to the respective tuner or modulator number (only
66	input devices have tuners, only output devices have modulators), zero
67	out the <structfield>reserved</structfield> array and
68	call the <constant>VIDIOC_G_FREQUENCY</constant> ioctl with a pointer
69	to 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
73	applications 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
77	call the <constant>VIDIOC_S_FREQUENCY</constant> ioctl with a pointer
78	to this structure. When the requested frequency is not possible the
79	driver assumes the closest possible value. However
80	<constant>VIDIOC_S_FREQUENCY</constant> is a write-only ioctl, it does
81	not 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
92	same value as in the &v4l2-input; <structfield>tuner</structfield>
93	field and the &v4l2-tuner; <structfield>index</structfield> field, or
94	the &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
102	to <constant>V4L2_TUNER_RADIO</constant> for <filename>/dev/radioX</filename>
103	device nodes, and to <constant>V4L2_TUNER_ANALOG_TV</constant>
104	for all others. Set this field to <constant>V4L2_TUNER_RADIO</constant> for
105	modulators (currently only radio modulators are supported).
106	See <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>capability</structfield> flag
113	<constant>V4L2_TUNER_CAP_LOW</constant> is set, in units of 62.5
114	Hz. A 1 Hz unit is used when the <structfield>capability</structfield> flag
115	<constant>V4L2_TUNER_CAP_1HZ</constant> is set.</entry>
116		  </row>
117		  <row>
118		    <entry>__u32</entry>
119		    <entry><structfield>reserved</structfield>[8]</entry>
120		    <entry>Reserved for future extensions. Drivers and
121		    applications must set the array to zero.</entry>
122		  </row>
123		</tbody>
124	      </tgroup>
125	    </table>
126	  </refsect1>
127	
128	  <refsect1>
129	    &return-value;
130	
131	    <variablelist>
132	      <varlistentry>
133		<term><errorcode>EINVAL</errorcode></term>
134		<listitem>
135		  <para>The <structfield>tuner</structfield> index is out of
136	bounds or the value in the <structfield>type</structfield> field is
137	wrong.</para>
138		</listitem>
139	      </varlistentry>
140	      <varlistentry>
141		<term><errorcode>EBUSY</errorcode></term>
142		<listitem>
143		  <para>A hardware seek is in progress.</para>
144		</listitem>
145	      </varlistentry>
146	    </variablelist>
147	  </refsect1>
148	</refentry>
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