Merge git://1984.lsi.us.es/nf-next
[cascardo/linux.git] / Documentation / DocBook / media / v4l / vidioc-enum-freq-bands.xml
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     <note>
53       <title>Experimental</title>
54       <para>This is an <link linkend="experimental"> experimental </link>
55       interface and may change in the future.</para>
56     </note>
57
58     <para>Enumerates the frequency bands that a tuner or modulator supports.
59 To do this applications initialize the <structfield>tuner</structfield>,
60 <structfield>type</structfield> and <structfield>index</structfield> fields,
61 and zero out the <structfield>reserved</structfield> array of a &v4l2-frequency-band; and
62 call the <constant>VIDIOC_ENUM_FREQ_BANDS</constant> ioctl with a pointer
63 to this structure.</para>
64
65     <para>This ioctl is supported if the <constant>V4L2_TUNER_CAP_FREQ_BANDS</constant> capability
66     of the corresponding tuner/modulator is set.</para>
67
68     <table pgwide="1" frame="none" id="v4l2-frequency-band">
69       <title>struct <structname>v4l2_frequency_band</structname></title>
70       <tgroup cols="3">
71         &cs-str;
72         <tbody valign="top">
73           <row>
74             <entry>__u32</entry>
75             <entry><structfield>tuner</structfield></entry>
76             <entry>The tuner or modulator index number. This is the
77 same value as in the &v4l2-input; <structfield>tuner</structfield>
78 field and the &v4l2-tuner; <structfield>index</structfield> field, or
79 the &v4l2-output; <structfield>modulator</structfield> field and the
80 &v4l2-modulator; <structfield>index</structfield> field.</entry>
81           </row>
82           <row>
83             <entry>__u32</entry>
84             <entry><structfield>type</structfield></entry>
85             <entry>The tuner type. This is the same value as in the
86 &v4l2-tuner; <structfield>type</structfield> field. The type must be set
87 to <constant>V4L2_TUNER_RADIO</constant> for <filename>/dev/radioX</filename>
88 device nodes, and to <constant>V4L2_TUNER_ANALOG_TV</constant>
89 for all others. Set this field to <constant>V4L2_TUNER_RADIO</constant> for
90 modulators (currently only radio modulators are supported).
91 See <xref linkend="v4l2-tuner-type" /></entry>
92           </row>
93           <row>
94             <entry>__u32</entry>
95             <entry><structfield>index</structfield></entry>
96             <entry>Identifies the frequency band, set by the application.</entry>
97           </row>
98           <row>
99             <entry>__u32</entry>
100             <entry><structfield>capability</structfield></entry>
101             <entry spanname="hspan">The tuner/modulator capability flags for
102 this frequency band, see <xref linkend="tuner-capability" />. The <constant>V4L2_TUNER_CAP_LOW</constant>
103 capability must be the same for all frequency bands of the selected tuner/modulator.
104 So either all bands have that capability set, or none of them have that capability.</entry>
105           </row>
106           <row>
107             <entry>__u32</entry>
108             <entry><structfield>rangelow</structfield></entry>
109             <entry spanname="hspan">The lowest tunable frequency in
110 units of 62.5 kHz, or if the <structfield>capability</structfield>
111 flag <constant>V4L2_TUNER_CAP_LOW</constant> is set, in units of 62.5
112 Hz, for this frequency band.</entry>
113           </row>
114           <row>
115             <entry>__u32</entry>
116             <entry><structfield>rangehigh</structfield></entry>
117             <entry spanname="hspan">The highest tunable frequency in
118 units of 62.5 kHz, or if the <structfield>capability</structfield>
119 flag <constant>V4L2_TUNER_CAP_LOW</constant> is set, in units of 62.5
120 Hz, for this frequency band.</entry>
121           </row>
122           <row>
123             <entry>__u32</entry>
124             <entry><structfield>modulation</structfield></entry>
125             <entry spanname="hspan">The supported modulation systems of this frequency band.
126             See <xref linkend="band-modulation" />. Note that currently only one
127             modulation system per frequency band is supported. More work will need to
128             be done if multiple modulation systems are possible. Contact the
129             linux-media mailing list (&v4l-ml;) if you need that functionality.</entry>
130           </row>
131           <row>
132             <entry>__u32</entry>
133             <entry><structfield>reserved</structfield>[9]</entry>
134             <entry>Reserved for future extensions. Applications and drivers
135             must set the array to zero.</entry>
136           </row>
137         </tbody>
138       </tgroup>
139     </table>
140
141     <table pgwide="1" frame="none" id="band-modulation">
142       <title>Band Modulation Systems</title>
143       <tgroup cols="3">
144         &cs-def;
145         <tbody valign="top">
146           <row>
147             <entry><constant>V4L2_BAND_MODULATION_VSB</constant></entry>
148             <entry>0x02</entry>
149             <entry>Vestigial Sideband modulation, used for analog TV.</entry>
150           </row>
151           <row>
152             <entry><constant>V4L2_BAND_MODULATION_FM</constant></entry>
153             <entry>0x04</entry>
154             <entry>Frequency Modulation, commonly used for analog radio.</entry>
155           </row>
156           <row>
157             <entry><constant>V4L2_BAND_MODULATION_AM</constant></entry>
158             <entry>0x08</entry>
159             <entry>Amplitude Modulation, commonly used for analog radio.</entry>
160           </row>
161         </tbody>
162       </tgroup>
163     </table>
164   </refsect1>
165
166   <refsect1>
167     &return-value;
168
169     <variablelist>
170       <varlistentry>
171         <term><errorcode>EINVAL</errorcode></term>
172         <listitem>
173           <para>The <structfield>tuner</structfield> or <structfield>index</structfield>
174 is out of bounds or the <structfield>type</structfield> field is wrong.</para>
175         </listitem>
176       </varlistentry>
177     </variablelist>
178   </refsect1>
179 </refentry>