Documentation/DocBook/media/v4l/vidioc-dqevent.xml

   1 <refentry id="vidioc-dqevent">
   2   <refmeta>
   3     <refentrytitle>ioctl VIDIOC_DQEVENT</refentrytitle>
   4     &manvol;
   5   </refmeta>
   6
   7   <refnamediv>
   8     <refname>VIDIOC_DQEVENT</refname>
   9     <refpurpose>Dequeue event</refpurpose>
  10   </refnamediv>
  11
  12   <refsynopsisdiv>
  13     <funcsynopsis>
  14       <funcprototype>
  15         <funcdef>int <function>ioctl</function></funcdef>
  16         <paramdef>int <parameter>fd</parameter></paramdef>
  17         <paramdef>int <parameter>request</parameter></paramdef>
  18         <paramdef>struct v4l2_event
  19 *<parameter>argp</parameter></paramdef>
  20       </funcprototype>
  21     </funcsynopsis>
  22   </refsynopsisdiv>
  23
  24   <refsect1>
  25     <title>Arguments</title>
  26
  27     <variablelist>
  28       <varlistentry>
  29         <term><parameter>fd</parameter></term>
  30         <listitem>
  31           <para>&fd;</para>
  32         </listitem>
  33       </varlistentry>
  34       <varlistentry>
  35         <term><parameter>request</parameter></term>
  36         <listitem>
  37           <para>VIDIOC_DQEVENT</para>
  38         </listitem>
  39       </varlistentry>
  40       <varlistentry>
  41         <term><parameter>argp</parameter></term>
  42         <listitem>
  43           <para></para>
  44         </listitem>
  45       </varlistentry>
  46     </variablelist>
  47   </refsect1>
  48
  49   <refsect1>
  50     <title>Description</title>
  51
  52     <para>Dequeue an event from a video device. No input is required
  53     for this ioctl. All the fields of the &v4l2-event; structure are
  54     filled by the driver. The file handle will also receive exceptions
  55     which the application may get by e.g. using the select system
  56     call.</para>
  57
  58     <table frame="none" pgwide="1" id="v4l2-event">
  59       <title>struct <structname>v4l2_event</structname></title>
  60       <tgroup cols="4">
  61         &cs-str;
  62         <tbody valign="top">
  63           <row>
  64             <entry>__u32</entry>
  65             <entry><structfield>type</structfield></entry>
  66             <entry></entry>
  67             <entry>Type of the event.</entry>
  68           </row>
  69           <row>
  70             <entry>union</entry>
  71             <entry><structfield>u</structfield></entry>
  72             <entry></entry>
  73             <entry></entry>
  74           </row>
  75           <row>
  76             <entry></entry>
  77             <entry>&v4l2-event-vsync;</entry>
  78             <entry><structfield>vsync</structfield></entry>
  79             <entry>Event data for event V4L2_EVENT_VSYNC.
  80             </entry>
  81           </row>
  82           <row>
  83             <entry></entry>
  84             <entry>&v4l2-event-ctrl;</entry>
  85             <entry><structfield>ctrl</structfield></entry>
  86             <entry>Event data for event V4L2_EVENT_CTRL.
  87             </entry>
  88           </row>
  89           <row>
  90             <entry></entry>
  91             <entry>__u8</entry>
  92             <entry><structfield>data</structfield>[64]</entry>
  93             <entry>Event data. Defined by the event type. The union
  94             should be used to define easily accessible type for
  95             events.</entry>
  96           </row>
  97           <row>
  98             <entry>__u32</entry>
  99             <entry><structfield>pending</structfield></entry>
 100             <entry></entry>
 101             <entry>Number of pending events excluding this one.</entry>
 102           </row>
 103           <row>
 104             <entry>__u32</entry>
 105             <entry><structfield>sequence</structfield></entry>
 106             <entry></entry>
 107             <entry>Event sequence number. The sequence number is
 108             incremented for every subscribed event that takes place.
 109             If sequence numbers are not contiguous it means that
 110             events have been lost.
 111             </entry>
 112           </row>
 113           <row>
 114             <entry>struct timespec</entry>
 115             <entry><structfield>timestamp</structfield></entry>
 116             <entry></entry>
 117             <entry>Event timestamp.</entry>
 118           </row>
 119           <row>
 120             <entry>u32</entry>
 121             <entry><structfield>id</structfield></entry>
 122             <entry></entry>
 123             <entry>The ID associated with the event source. If the event does not
 124                 have an associated ID (this depends on the event type), then this
 125                 is 0.</entry>
 126           </row>
 127           <row>
 128             <entry>__u32</entry>
 129             <entry><structfield>reserved</structfield>[8]</entry>
 130             <entry></entry>
 131             <entry>Reserved for future extensions. Drivers must set
 132             the array to zero.</entry>
 133           </row>
 134         </tbody>
 135       </tgroup>
 136     </table>
 137
 138   </refsect1>
 139   <refsect1>
 140     &return-value;
 141   </refsect1>
 142 </refentry>