V4L/DVB: V4L: Events: Add documentation

Add documentation on how to use V4L2 events, both for V4L2 drivers and for
V4L2 applications.

Signed-off-by: Sakari Ailus <sakari.ailus@maxwell.research.nokia.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

1 files changed, 124 insertions, 0 deletions

diff --git a/Documentation/DocBook/v4l/vidioc-dqevent.xml b/Documentation/DocBook/v4l/vidioc-dqevent.xml
new file mode 100644
index 000000000000..eb45c1695d8c
--- /dev/null
+++ b/Documentation/DocBook/v4l/vidioc-dqevent.xml
@@ -0,0 +1,124 @@
+<refentry id="vidioc-dqevent">
+  <refmeta>
+    <refentrytitle>ioctl VIDIOC_DQEVENT</refentrytitle>
+    &manvol;
+  </refmeta>
+
+  <refnamediv>
+    <refname>VIDIOC_DQEVENT</refname>
+    <refpurpose>Dequeue event</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_event
+*<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_DQEVENT</para>
+	</listitem>
+      </varlistentry>
+      <varlistentry>
+	<term><parameter>argp</parameter></term>
+	<listitem>
+	  <para></para>
+	</listitem>
+      </varlistentry>
+    </variablelist>
+  </refsect1>
+
+  <refsect1>
+    <title>Description</title>
+
+    <para>Dequeue an event from a video device. No input is required
+    for this ioctl. All the fields of the &v4l2-event; structure are
+    filled by the driver. The file handle will also receive exceptions
+    which the application may get by e.g. using the select system
+    call.</para>
+
+    <table frame="none" pgwide="1" id="v4l2-event">
+      <title>struct <structname>v4l2_event</structname></title>
+      <tgroup cols="4">
+	&cs-str;
+	<tbody valign="top">
+	  <row>
+	    <entry>__u32</entry>
+	    <entry><structfield>type</structfield></entry>
+            <entry></entry>
+	    <entry>Type of the event.</entry>
+	  </row>
+	  <row>
+	    <entry>union</entry>
+	    <entry><structfield>u</structfield></entry>
+            <entry></entry>
+	    <entry></entry>
+	  </row>
+	  <row>
+	    <entry></entry>
+	    <entry>__u8</entry>
+            <entry><structfield>data</structfield>[64]</entry>
+	    <entry>Event data. Defined by the event type. The union
+            should be used to define easily accessible type for
+            events.</entry>
+	  </row>
+	  <row>
+	    <entry>__u32</entry>
+	    <entry><structfield>pending</structfield></entry>
+            <entry></entry>
+	    <entry>Number of pending events excluding this one.</entry>
+	  </row>
+	  <row>
+	    <entry>__u32</entry>
+	    <entry><structfield>sequence</structfield></entry>
+            <entry></entry>
+	    <entry>Event sequence number. The sequence number is
+	    incremented for every subscribed event that takes place.
+	    If sequence numbers are not contiguous it means that
+	    events have been lost.
+	    </entry>
+	  </row>
+	  <row>
+	    <entry>struct timeval</entry>
+	    <entry><structfield>timestamp</structfield></entry>
+            <entry></entry>
+	    <entry>Event timestamp.</entry>
+	  </row>
+	  <row>
+	    <entry>__u32</entry>
+	    <entry><structfield>reserved</structfield>[9]</entry>
+            <entry></entry>
+	    <entry>Reserved for future extensions. Drivers must set
+	    the array to zero.</entry>
+	  </row>
+	</tbody>
+      </tgroup>
+    </table>
+
+  </refsect1>
+</refentry>
+<!--
+Local Variables:
+mode: sgml
+sgml-parent-document: "v4l2.sgml"
+indent-tabs-mode: nil
+End:
+-->