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Based on kernel version 4.7.2. Page generated on 2016-08-22 22:45 EST.

1	<refentry id="vidioc-enum-freq-bands">
2	  <refmeta>
3	    <refentrytitle>ioctl VIDIOC_ENUM_FREQ_BANDS</refentrytitle>
4	    &manvol;
5	  </refmeta>
6	
7	  <refnamediv>
8	    <refname>VIDIOC_ENUM_FREQ_BANDS</refname>
9	    <refpurpose>Enumerate supported frequency bands</refpurpose>
10	  </refnamediv>
11	
12	  <refsynopsisdiv>
13	    <funcsynopsis>
14	      <funcprototype>
15		<funcdef>int <function>ioctl</function></funcdef>
16		<paramdef>int <parameter>fd</parameter></paramdef>
17		<paramdef>int <parameter>request</parameter></paramdef>
18		<paramdef>struct v4l2_frequency_band
19	*<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_ENUM_FREQ_BANDS</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>Enumerates the frequency bands that a tuner or modulator supports.
53	To do this applications initialize the <structfield>tuner</structfield>,
54	<structfield>type</structfield> and <structfield>index</structfield> fields,
55	and zero out the <structfield>reserved</structfield> array of a &v4l2-frequency-band; and
56	call the <constant>VIDIOC_ENUM_FREQ_BANDS</constant> ioctl with a pointer
57	to this structure.</para>
58	
59	    <para>This ioctl is supported if the <constant>V4L2_TUNER_CAP_FREQ_BANDS</constant> capability
60	    of the corresponding tuner/modulator is set.</para>
61	
62	    <table pgwide="1" frame="none" id="v4l2-frequency-band">
63	      <title>struct <structname>v4l2_frequency_band</structname></title>
64	      <tgroup cols="3">
65		&cs-str;
66		<tbody valign="top">
67		  <row>
68		    <entry>__u32</entry>
69		    <entry><structfield>tuner</structfield></entry>
70		    <entry>The tuner or modulator index number. This is the
71	same value as in the &v4l2-input; <structfield>tuner</structfield>
72	field and the &v4l2-tuner; <structfield>index</structfield> field, or
73	the &v4l2-output; <structfield>modulator</structfield> field and the
74	&v4l2-modulator; <structfield>index</structfield> field.</entry>
75		  </row>
76		  <row>
77		    <entry>__u32</entry>
78		    <entry><structfield>type</structfield></entry>
79		    <entry>The tuner type. This is the same value as in the
80	&v4l2-tuner; <structfield>type</structfield> field. The type must be set
81	to <constant>V4L2_TUNER_RADIO</constant> for <filename>/dev/radioX</filename>
82	device nodes, and to <constant>V4L2_TUNER_ANALOG_TV</constant>
83	for all others. Set this field to <constant>V4L2_TUNER_RADIO</constant> for
84	modulators (currently only radio modulators are supported).
85	See <xref linkend="v4l2-tuner-type" /></entry>
86		  </row>
87		  <row>
88		    <entry>__u32</entry>
89		    <entry><structfield>index</structfield></entry>
90		    <entry>Identifies the frequency band, set by the application.</entry>
91		  </row>
92		  <row>
93		    <entry>__u32</entry>
94		    <entry><structfield>capability</structfield></entry>
95		    <entry spanname="hspan">The tuner/modulator capability flags for
96	this frequency band, see <xref linkend="tuner-capability" />. The <constant>V4L2_TUNER_CAP_LOW</constant>
97	or <constant>V4L2_TUNER_CAP_1HZ</constant> capability must be the same for all frequency bands of the selected tuner/modulator.
98	So either all bands have that capability set, or none of them have that capability.</entry>
99		  </row>
100		  <row>
101		    <entry>__u32</entry>
102		    <entry><structfield>rangelow</structfield></entry>
103		    <entry spanname="hspan">The lowest tunable frequency in
104	units of 62.5 kHz, or if the <structfield>capability</structfield>
105	flag <constant>V4L2_TUNER_CAP_LOW</constant> is set, in units of 62.5
106	Hz, for this frequency band. A 1 Hz unit is used when the <structfield>capability</structfield> flag
107	<constant>V4L2_TUNER_CAP_1HZ</constant> is set.</entry>
108		  </row>
109		  <row>
110		    <entry>__u32</entry>
111		    <entry><structfield>rangehigh</structfield></entry>
112		    <entry spanname="hspan">The highest tunable frequency in
113	units of 62.5 kHz, or if the <structfield>capability</structfield>
114	flag <constant>V4L2_TUNER_CAP_LOW</constant> is set, in units of 62.5
115	Hz, for this frequency band. A 1 Hz unit is used when the <structfield>capability</structfield> flag
116	<constant>V4L2_TUNER_CAP_1HZ</constant> is set.</entry>
117		  </row>
118		  <row>
119		    <entry>__u32</entry>
120		    <entry><structfield>modulation</structfield></entry>
121		    <entry spanname="hspan">The supported modulation systems of this frequency band.
122		    See <xref linkend="band-modulation" />. Note that currently only one
123		    modulation system per frequency band is supported. More work will need to
124		    be done if multiple modulation systems are possible. Contact the
125		    linux-media mailing list (&v4l-ml;) if you need that functionality.</entry>
126		  </row>
127		  <row>
128		    <entry>__u32</entry>
129		    <entry><structfield>reserved</structfield>[9]</entry>
130		    <entry>Reserved for future extensions. Applications and drivers
131		    must set the array to zero.</entry>
132		  </row>
133		</tbody>
134	      </tgroup>
135	    </table>
136	
137	    <table pgwide="1" frame="none" id="band-modulation">
138	      <title>Band Modulation Systems</title>
139	      <tgroup cols="3">
140		&cs-def;
141		<tbody valign="top">
142		  <row>
143		    <entry><constant>V4L2_BAND_MODULATION_VSB</constant></entry>
144		    <entry>0x02</entry>
145		    <entry>Vestigial Sideband modulation, used for analog TV.</entry>
146		  </row>
147		  <row>
148		    <entry><constant>V4L2_BAND_MODULATION_FM</constant></entry>
149		    <entry>0x04</entry>
150		    <entry>Frequency Modulation, commonly used for analog radio.</entry>
151		  </row>
152		  <row>
153		    <entry><constant>V4L2_BAND_MODULATION_AM</constant></entry>
154		    <entry>0x08</entry>
155		    <entry>Amplitude Modulation, commonly used for analog radio.</entry>
156		  </row>
157		</tbody>
158	      </tgroup>
159	    </table>
160	  </refsect1>
161	
162	  <refsect1>
163	    &return-value;
164	
165	    <variablelist>
166	      <varlistentry>
167		<term><errorcode>EINVAL</errorcode></term>
168		<listitem>
169		  <para>The <structfield>tuner</structfield> or <structfield>index</structfield>
170	is out of bounds or the <structfield>type</structfield> field is wrong.</para>
171		</listitem>
172	      </varlistentry>
173	    </variablelist>
174	  </refsect1>
175	</refentry>
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