Add the rt linux 4.1.3-rt3 as base

[kvmfornfv.git] / kernel / Documentation / DocBook / media / v4l / vidioc-g-audioout.xml

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+<refentry id="vidioc-g-audioout">
+  <refmeta>
+    <refentrytitle>ioctl VIDIOC_G_AUDOUT, VIDIOC_S_AUDOUT</refentrytitle>
+    &manvol;
+  </refmeta>
+
+  <refnamediv>
+    <refname>VIDIOC_G_AUDOUT</refname>
+    <refname>VIDIOC_S_AUDOUT</refname>
+    <refpurpose>Query or select the current audio output</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_audioout *<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_audioout *<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_AUDOUT, VIDIOC_S_AUDOUT</para>
+       </listitem>
+      </varlistentry>
+      <varlistentry>
+       <term><parameter>argp</parameter></term>
+       <listitem>
+         <para></para>
+       </listitem>
+      </varlistentry>
+    </variablelist>
+  </refsect1>
+
+  <refsect1>
+    <title>Description</title>
+
+    <para>To query the current audio output applications zero out the
+<structfield>reserved</structfield> array of a &v4l2-audioout; and
+call the <constant>VIDIOC_G_AUDOUT</constant> ioctl with a pointer
+to this structure. Drivers fill the rest of the structure or return an
+&EINVAL; when the device has no audio inputs, or none which combine
+with the current video output.</para>
+
+    <para>Audio outputs have no writable properties. Nevertheless, to
+select the current audio output applications can initialize the
+<structfield>index</structfield> field and
+<structfield>reserved</structfield> array (which in the future may
+contain writable properties) of a
+<structname>v4l2_audioout</structname> structure and call the
+<constant>VIDIOC_S_AUDOUT</constant> ioctl. Drivers switch to the
+requested output or return the &EINVAL; when the index is out of
+bounds. This is a write-only ioctl, it does not return the current
+audio output attributes as <constant>VIDIOC_G_AUDOUT</constant>
+does.</para>
+
+    <para>Note connectors on a TV card to loop back the received audio
+signal to a sound card are not audio outputs in this sense.</para>
+
+    <table pgwide="1" frame="none" id="v4l2-audioout">
+      <title>struct <structname>v4l2_audioout</structname></title>
+      <tgroup cols="3">
+       &cs-str;
+       <tbody valign="top">
+         <row>
+           <entry>__u32</entry>
+           <entry><structfield>index</structfield></entry>
+           <entry>Identifies the audio output, set by the
+driver or application.</entry>
+         </row>
+         <row>
+           <entry>__u8</entry>
+           <entry><structfield>name</structfield>[32]</entry>
+           <entry>Name of the audio output, a NUL-terminated ASCII
+string, for example: "Line Out". This information is intended for the
+user, preferably the connector label on the device itself.</entry>
+         </row>
+         <row>
+           <entry>__u32</entry>
+           <entry><structfield>capability</structfield></entry>
+           <entry>Audio capability flags, none defined yet. Drivers
+must set this field to zero.</entry>
+         </row>
+         <row>
+           <entry>__u32</entry>
+           <entry><structfield>mode</structfield></entry>
+           <entry>Audio mode, none defined yet. Drivers and
+applications (on <constant>VIDIOC_S_AUDOUT</constant>) must set this
+field to zero.</entry>
+         </row>
+         <row>
+           <entry>__u32</entry>
+           <entry><structfield>reserved</structfield>[2]</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>No audio outputs combine with the current video
+output, or the number of the selected audio output is out of bounds or
+it does not combine.</para>
+       </listitem>
+      </varlistentry>
+    </variablelist>
+  </refsect1>
+</refentry>