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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>
- <note>
- <title>Experimental</title>
- <para>This is an <link linkend="experimental"> experimental </link>
- interface and may change in the future.</para>
- </note>
- <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>
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