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<refentry id="vidioc-enum-freq-bands">
<refmeta>
<refentrytitle>ioctl VIDIOC_ENUM_FREQ_BANDS</refentrytitle>
&manvol;
</refmeta>
<refnamediv>
<refname>VIDIOC_ENUM_FREQ_BANDS</refname>
<refpurpose>Enumerate supported frequency bands</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_band
*<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_ENUM_FREQ_BANDS</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>argp</parameter></term>
<listitem>
<para></para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Description</title>
<para>Enumerates the frequency bands that a tuner or modulator supports.
To do this applications initialize the <structfield>tuner</structfield>,
<structfield>type</structfield> and <structfield>index</structfield> fields,
and zero out the <structfield>reserved</structfield> array of a &v4l2-frequency-band; and
call the <constant>VIDIOC_ENUM_FREQ_BANDS</constant> ioctl with a pointer
to this structure.</para>
<para>This ioctl is supported if the <constant>V4L2_TUNER_CAP_FREQ_BANDS</constant> capability
of the corresponding tuner/modulator is set.</para>
<table pgwide="1" frame="none" id="v4l2-frequency-band">
<title>struct <structname>v4l2_frequency_band</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>__u32</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. Set this field to <constant>V4L2_TUNER_RADIO</constant> for
modulators (currently only radio modulators are supported).
See <xref linkend="v4l2-tuner-type" /></entry>
</row>
<row>
<entry>__u32</entry>
<entry><structfield>index</structfield></entry>
<entry>Identifies the frequency band, set by the application.</entry>
</row>
<row>
<entry>__u32</entry>
<entry><structfield>capability</structfield></entry>
<entry spanname="hspan">The tuner/modulator capability flags for
this frequency band, see <xref linkend="tuner-capability" />. The <constant>V4L2_TUNER_CAP_LOW</constant>
or <constant>V4L2_TUNER_CAP_1HZ</constant> capability must be the same for all frequency bands of the selected tuner/modulator.
So either all bands have that capability set, or none of them have that capability.</entry>
</row>
<row>
<entry>__u32</entry>
<entry><structfield>rangelow</structfield></entry>
<entry spanname="hspan">The lowest tunable frequency in
units of 62.5 kHz, or if the <structfield>capability</structfield>
flag <constant>V4L2_TUNER_CAP_LOW</constant> is set, in units of 62.5
Hz, for this frequency band. A 1 Hz unit is used when the <structfield>capability</structfield> flag
<constant>V4L2_TUNER_CAP_1HZ</constant> is set.</entry>
</row>
<row>
<entry>__u32</entry>
<entry><structfield>rangehigh</structfield></entry>
<entry spanname="hspan">The highest tunable frequency in
units of 62.5 kHz, or if the <structfield>capability</structfield>
flag <constant>V4L2_TUNER_CAP_LOW</constant> is set, in units of 62.5
Hz, for this frequency band. A 1 Hz unit is used when the <structfield>capability</structfield> flag
<constant>V4L2_TUNER_CAP_1HZ</constant> is set.</entry>
</row>
<row>
<entry>__u32</entry>
<entry><structfield>modulation</structfield></entry>
<entry spanname="hspan">The supported modulation systems of this frequency band.
See <xref linkend="band-modulation" />. Note that currently only one
modulation system per frequency band is supported. More work will need to
be done if multiple modulation systems are possible. Contact the
linux-media mailing list (&v4l-ml;) if you need that functionality.</entry>
</row>
<row>
<entry>__u32</entry>
<entry><structfield>reserved</structfield>[9]</entry>
<entry>Reserved for future extensions. Applications and drivers
must set the array to zero.</entry>
</row>
</tbody>
</tgroup>
</table>
<table pgwide="1" frame="none" id="band-modulation">
<title>Band Modulation Systems</title>
<tgroup cols="3">
&cs-def;
<tbody valign="top">
<row>
<entry><constant>V4L2_BAND_MODULATION_VSB</constant></entry>
<entry>0x02</entry>
<entry>Vestigial Sideband modulation, used for analog TV.</entry>
</row>
<row>
<entry><constant>V4L2_BAND_MODULATION_FM</constant></entry>
<entry>0x04</entry>
<entry>Frequency Modulation, commonly used for analog radio.</entry>
</row>
<row>
<entry><constant>V4L2_BAND_MODULATION_AM</constant></entry>
<entry>0x08</entry>
<entry>Amplitude Modulation, commonly used for analog radio.</entry>
</row>
</tbody>
</tgroup>
</table>
</refsect1>
<refsect1>
&return-value;
<variablelist>
<varlistentry>
<term><errorcode>EINVAL</errorcode></term>
<listitem>
<para>The <structfield>tuner</structfield> or <structfield>index</structfield>
is out of bounds or the <structfield>type</structfield> field is wrong.</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
</refentry>
|
