[media] v4l2 spec: add VIDIOC_ENUM_FREQ_BANDS documentation

Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

1 files changed, 179 insertions, 0 deletions

diff --git a/Documentation/DocBook/media/v4l/vidioc-enum-freq-bands.xml b/Documentation/DocBook/media/v4l/vidioc-enum-freq-bands.xml
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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>
+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.</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.</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>