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<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 type must be set
to <constant>V4L2_TUNER_RADIO</constant> for <filename>/dev/radioX</filename>
device nodes, and to <constant>V4L2_TUNER_ANALOG_TV</constant>
for all others. 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>
|
