summaryrefslogtreecommitdiff
path: root/Documentation/DocBook/media/v4l/vidioc-g-frequency.xml
blob: 062d720690906b3993327e88fdd05db47f249037 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
<refentry id="vidioc-g-frequency">
  <refmeta>
    <refentrytitle>ioctl VIDIOC_G_FREQUENCY, VIDIOC_S_FREQUENCY</refentrytitle>
    &manvol;
  </refmeta>

  <refnamediv>
    <refname>VIDIOC_G_FREQUENCY</refname>
    <refname>VIDIOC_S_FREQUENCY</refname>
    <refpurpose>Get or set tuner or modulator radio
frequency</refpurpose>
  </refnamediv>

  <refsynopsisdiv>
    <funcsynopsis>
      <funcprototype>
	<funcdef>int <function>ioctl</function></funcdef>
	<paramdef>int <parameter>fd</parameter></paramdef>
	<paramdef>int <parameter>request</parameter></paramdef>
	<paramdef>struct v4l2_frequency
*<parameter>argp</parameter></paramdef>
      </funcprototype>
    </funcsynopsis>
    <funcsynopsis>
      <funcprototype>
	<funcdef>int <function>ioctl</function></funcdef>
	<paramdef>int <parameter>fd</parameter></paramdef>
	<paramdef>int <parameter>request</parameter></paramdef>
	<paramdef>const struct v4l2_frequency
*<parameter>argp</parameter></paramdef>
      </funcprototype>
    </funcsynopsis>
  </refsynopsisdiv>

  <refsect1>
    <title>Arguments</title>

    <variablelist>
      <varlistentry>
	<term><parameter>fd</parameter></term>
	<listitem>
	  <para>&fd;</para>
	</listitem>
      </varlistentry>
      <varlistentry>
	<term><parameter>request</parameter></term>
	<listitem>
	  <para>VIDIOC_G_FREQUENCY, VIDIOC_S_FREQUENCY</para>
	</listitem>
      </varlistentry>
      <varlistentry>
	<term><parameter>argp</parameter></term>
	<listitem>
	  <para></para>
	</listitem>
      </varlistentry>
    </variablelist>
  </refsect1>

  <refsect1>
    <title>Description</title>

    <para>To get the current tuner or modulator radio frequency
applications set the <structfield>tuner</structfield> field of a
&v4l2-frequency; to the respective tuner or modulator number (only
input devices have tuners, only output devices have modulators), zero
out the <structfield>reserved</structfield> array and
call the <constant>VIDIOC_G_FREQUENCY</constant> ioctl with a pointer
to this structure. The driver stores the current frequency in the
<structfield>frequency</structfield> field.</para>

    <para>To change the current tuner or modulator radio frequency
applications initialize the <structfield>tuner</structfield>,
<structfield>type</structfield> and
<structfield>frequency</structfield> fields, and the
<structfield>reserved</structfield> array of a &v4l2-frequency; and
call the <constant>VIDIOC_S_FREQUENCY</constant> ioctl with a pointer
to this structure. When the requested frequency is not possible the
driver assumes the closest possible value. However
<constant>VIDIOC_S_FREQUENCY</constant> is a write-only ioctl, it does
not return the actual new frequency.</para>

    <table pgwide="1" frame="none" id="v4l2-frequency">
      <title>struct <structname>v4l2_frequency</structname></title>
      <tgroup cols="3">
	&cs-str;
	<tbody valign="top">
	  <row>
	    <entry>__u32</entry>
	    <entry><structfield>tuner</structfield></entry>
	    <entry>The tuner or modulator index number. This is the
same value as in the &v4l2-input; <structfield>tuner</structfield>
field and the &v4l2-tuner; <structfield>index</structfield> field, or
the &v4l2-output; <structfield>modulator</structfield> field and the
&v4l2-modulator; <structfield>index</structfield> field.</entry>
	  </row>
	  <row>
	    <entry>&v4l2-tuner-type;</entry>
	    <entry><structfield>type</structfield></entry>
	    <entry>The tuner type. This is the same value as in the
&v4l2-tuner; <structfield>type</structfield> field. The field is not
applicable to modulators, &ie; ignored by drivers.</entry>
	  </row>
	  <row>
	    <entry>__u32</entry>
	    <entry><structfield>frequency</structfield></entry>
	    <entry>Tuning frequency in units of 62.5 kHz, or if the
&v4l2-tuner; or &v4l2-modulator; <structfield>capabilities</structfield> flag
<constant>V4L2_TUNER_CAP_LOW</constant> is set, in units of 62.5
Hz.</entry>
	  </row>
	  <row>
	    <entry>__u32</entry>
	    <entry><structfield>reserved</structfield>[8]</entry>
	    <entry>Reserved for future extensions. Drivers and
	    applications must set the array to zero.</entry>
	  </row>
	</tbody>
      </tgroup>
    </table>
  </refsect1>

  <refsect1>
    &return-value;

    <variablelist>
      <varlistentry>
	<term><errorcode>EINVAL</errorcode></term>
	<listitem>
	  <para>The <structfield>tuner</structfield> index is out of
bounds or the value in the <structfield>type</structfield> field is
wrong.</para>
	</listitem>
      </varlistentry>
    </variablelist>
  </refsect1>
</refentry>

<!--
Local Variables:
mode: sgml
sgml-parent-document: "v4l2.sgml"
indent-tabs-mode: nil
End:
-->