<refentry id="vidioc-subscribe-event">
  <refmeta>
    <refentrytitle>ioctl VIDIOC_SUBSCRIBE_EVENT, VIDIOC_UNSUBSCRIBE_EVENT</refentrytitle>
    &manvol;
  </refmeta>

  <refnamediv>
    <refname>VIDIOC_SUBSCRIBE_EVENT, VIDIOC_UNSUBSCRIBE_EVENT</refname>
    <refpurpose>Subscribe or unsubscribe 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_subscription
*<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_SUBSCRIBE_EVENT, VIDIOC_UNSUBSCRIBE_EVENT</para>
	</listitem>
      </varlistentry>
      <varlistentry>
	<term><parameter>argp</parameter></term>
	<listitem>
	  <para></para>
	</listitem>
      </varlistentry>
    </variablelist>
  </refsect1>

  <refsect1>
    <title>Description</title>

    <para>Subscribe or unsubscribe V4L2 event. Subscribed events are
    dequeued by using the &VIDIOC-DQEVENT; ioctl.</para>

    <table frame="none" pgwide="1" id="v4l2-event-subscription">
      <title>struct <structname>v4l2_event_subscription</structname></title>
      <tgroup cols="3">
	&cs-str;
	<tbody valign="top">
	  <row>
	    <entry>__u32</entry>
	    <entry><structfield>type</structfield></entry>
	    <entry>Type of the event.</entry>
	  </row>
	  <row>
	    <entry>__u32</entry>
	    <entry><structfield>reserved</structfield>[7]</entry>
	    <entry>Reserved for future extensions. Drivers and applications
	    must set the array to zero.</entry>
	  </row>
	</tbody>
      </tgroup>
    </table>

    <table frame="none" pgwide="1" id="event-type">
      <title>Event Types</title>
      <tgroup cols="3">
	&cs-def;
	<tbody valign="top">
	  <row>
	    <entry><constant>V4L2_EVENT_ALL</constant></entry>
	    <entry>0</entry>
	    <entry>All events. V4L2_EVENT_ALL is valid only for
	    VIDIOC_UNSUBSCRIBE_EVENT for unsubscribing all events at once.
	    </entry>
	  </row>
	  <row>
	    <entry><constant>V4L2_EVENT_VSYNC</constant></entry>
	    <entry>1</entry>
	    <entry>This event is triggered on the vertical sync.
	    This event has &v4l2-event-vsync; associated with it.
	    </entry>
	  </row>
	  <row>
	    <entry><constant>V4L2_EVENT_EOS</constant></entry>
	    <entry>2</entry>
	    <entry>This event is triggered when the end of a stream is reached.
	    This is typically used with MPEG decoders to report to the application
	    when the last of the MPEG stream has been decoded.
	    </entry>
	  </row>
	  <row>
	    <entry><constant>V4L2_EVENT_PRIVATE_START</constant></entry>
	    <entry>0x08000000</entry>
	    <entry>Base event number for driver-private events.</entry>
	  </row>
	</tbody>
      </tgroup>
    </table>

    <table frame="none" pgwide="1" id="v4l2-event-vsync">
      <title>struct <structname>v4l2_event_vsync</structname></title>
      <tgroup cols="3">
	&cs-str;
	<tbody valign="top">
	  <row>
	    <entry>__u8</entry>
	    <entry><structfield>field</structfield></entry>
	    <entry>The upcoming field. See &v4l2-field;.</entry>
	  </row>
	</tbody>
      </tgroup>
    </table>

  </refsect1>
</refentry>
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