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 <constant>V4L2_EVENT_VSYNC</constant>.
  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 <constant>V4L2_EVENT_CTRL</constant>.
  87             </entry>
  88           </row>
  89           <row>
  90             <entry></entry>
  91             <entry>&v4l2-event-frame-sync;</entry>
  92             <entry><structfield>frame_sync</structfield></entry>
  93             <entry>Event data for event
  94             <constant>V4L2_EVENT_FRAME_SYNC</constant>.</entry>
  95           </row>
  96           <row>
  97             <entry></entry>
  98             <entry>&v4l2-event-motion-det;</entry>
  99             <entry><structfield>motion_det</structfield></entry>
 100             <entry>Event data for event V4L2_EVENT_MOTION_DET.</entry>
 101           </row>
 102           <row>
 103             <entry></entry>
 104             <entry>&v4l2-event-src-change;</entry>
 105             <entry><structfield>src_change</structfield></entry>
 106             <entry>Event data for event V4L2_EVENT_SOURCE_CHANGE.</entry>
 107           </row>
 108           <row>
 109             <entry></entry>
 110             <entry>__u8</entry>
 111             <entry><structfield>data</structfield>[64]</entry>
 112             <entry>Event data. Defined by the event type. The union
 113             should be used to define easily accessible type for
 114             events.</entry>
 115           </row>
 116           <row>
 117             <entry>__u32</entry>
 118             <entry><structfield>pending</structfield></entry>
 119             <entry></entry>
 120             <entry>Number of pending events excluding this one.</entry>
 121           </row>
 122           <row>
 123             <entry>__u32</entry>
 124             <entry><structfield>sequence</structfield></entry>
 125             <entry></entry>
 126             <entry>Event sequence number. The sequence number is
 127             incremented for every subscribed event that takes place.
 128             If sequence numbers are not contiguous it means that
 129             events have been lost.
 130             </entry>
 131           </row>
 132           <row>
 133             <entry>struct timespec</entry>
 134             <entry><structfield>timestamp</structfield></entry>
 135             <entry></entry>
 136             <entry>Event timestamp.</entry>
 137           </row>
 138           <row>
 139             <entry>u32</entry>
 140             <entry><structfield>id</structfield></entry>
 141             <entry></entry>
 142             <entry>The ID associated with the event source. If the event does not
 143                 have an associated ID (this depends on the event type), then this
 144                 is 0.</entry>
 145           </row>
 146           <row>
 147             <entry>__u32</entry>
 148             <entry><structfield>reserved</structfield>[8]</entry>
 149             <entry></entry>
 150             <entry>Reserved for future extensions. Drivers must set
 151             the array to zero.</entry>
 152           </row>
 153         </tbody>
 154       </tgroup>
 155     </table>
 156
 157     <table frame="none" pgwide="1" id="v4l2-event-vsync">
 158       <title>struct <structname>v4l2_event_vsync</structname></title>
 159       <tgroup cols="3">
 160         &cs-str;
 161         <tbody valign="top">
 162           <row>
 163             <entry>__u8</entry>
 164             <entry><structfield>field</structfield></entry>
 165             <entry>The upcoming field. See &v4l2-field;.</entry>
 166           </row>
 167         </tbody>
 168       </tgroup>
 169     </table>
 170
 171     <table frame="none" pgwide="1" id="v4l2-event-ctrl">
 172       <title>struct <structname>v4l2_event_ctrl</structname></title>
 173       <tgroup cols="4">
 174         &cs-str;
 175         <tbody valign="top">
 176           <row>
 177             <entry>__u32</entry>
 178             <entry><structfield>changes</structfield></entry>
 179             <entry></entry>
 180             <entry>A bitmask that tells what has changed. See <xref linkend="changes-flags" />.</entry>
 181           </row>
 182           <row>
 183             <entry>__u32</entry>
 184             <entry><structfield>type</structfield></entry>
 185             <entry></entry>
 186             <entry>The type of the control. See &v4l2-ctrl-type;.</entry>
 187           </row>
 188           <row>
 189             <entry>union (anonymous)</entry>
 190             <entry></entry>
 191             <entry></entry>
 192             <entry></entry>
 193           </row>
 194           <row>
 195             <entry></entry>
 196             <entry>__s32</entry>
 197             <entry><structfield>value</structfield></entry>
 198             <entry>The 32-bit value of the control for 32-bit control types.
 199                 This is 0 for string controls since the value of a string
 200                 cannot be passed using &VIDIOC-DQEVENT;.</entry>
 201           </row>
 202           <row>
 203             <entry></entry>
 204             <entry>__s64</entry>
 205             <entry><structfield>value64</structfield></entry>
 206             <entry>The 64-bit value of the control for 64-bit control types.</entry>
 207           </row>
 208           <row>
 209             <entry>__u32</entry>
 210             <entry><structfield>flags</structfield></entry>
 211             <entry></entry>
 212             <entry>The control flags. See <xref linkend="control-flags" />.</entry>
 213           </row>
 214           <row>
 215             <entry>__s32</entry>
 216             <entry><structfield>minimum</structfield></entry>
 217             <entry></entry>
 218             <entry>The minimum value of the control. See &v4l2-queryctrl;.</entry>
 219           </row>
 220           <row>
 221             <entry>__s32</entry>
 222             <entry><structfield>maximum</structfield></entry>
 223             <entry></entry>
 224             <entry>The maximum value of the control. See &v4l2-queryctrl;.</entry>
 225           </row>
 226           <row>
 227             <entry>__s32</entry>
 228             <entry><structfield>step</structfield></entry>
 229             <entry></entry>
 230             <entry>The step value of the control. See &v4l2-queryctrl;.</entry>
 231           </row>
 232           <row>
 233             <entry>__s32</entry>
 234             <entry><structfield>default_value</structfield></entry>
 235             <entry></entry>
 236             <entry>The default value value of the control. See &v4l2-queryctrl;.</entry>
 237           </row>
 238         </tbody>
 239       </tgroup>
 240     </table>
 241
 242     <table frame="none" pgwide="1" id="v4l2-event-frame-sync">
 243       <title>struct <structname>v4l2_event_frame_sync</structname></title>
 244       <tgroup cols="3">
 245         &cs-str;
 246         <tbody valign="top">
 247           <row>
 248             <entry>__u32</entry>
 249             <entry><structfield>frame_sequence</structfield></entry>
 250             <entry>
 251               The sequence number of the frame being received.
 252             </entry>
 253           </row>
 254         </tbody>
 255       </tgroup>
 256     </table>
 257
 258     <table frame="none" pgwide="1" id="v4l2-event-src-change">
 259       <title>struct <structname>v4l2_event_src_change</structname></title>
 260       <tgroup cols="3">
 261         &cs-str;
 262         <tbody valign="top">
 263           <row>
 264             <entry>__u32</entry>
 265             <entry><structfield>changes</structfield></entry>
 266             <entry>
 267               A bitmask that tells what has changed. See <xref linkend="src-changes-flags" />.
 268             </entry>
 269           </row>
 270         </tbody>
 271       </tgroup>
 272     </table>
 273
 274     <table frame="none" pgwide="1" id="v4l2-event-motion-det">
 275       <title>struct <structname>v4l2_event_motion_det</structname></title>
 276       <tgroup cols="3">
 277         &cs-str;
 278         <tbody valign="top">
 279           <row>
 280             <entry>__u32</entry>
 281             <entry><structfield>flags</structfield></entry>
 282             <entry>
 283               Currently only one flag is available: if <constant>V4L2_EVENT_MD_FL_HAVE_FRAME_SEQ</constant>
 284               is set, then the <structfield>frame_sequence</structfield> field is valid,
 285               otherwise that field should be ignored.
 286             </entry>
 287           </row>
 288           <row>
 289             <entry>__u32</entry>
 290             <entry><structfield>frame_sequence</structfield></entry>
 291             <entry>
 292               The sequence number of the frame being received. Only valid if the
 293               <constant>V4L2_EVENT_MD_FL_HAVE_FRAME_SEQ</constant> flag was set.
 294             </entry>
 295           </row>
 296           <row>
 297             <entry>__u32</entry>
 298             <entry><structfield>region_mask</structfield></entry>
 299             <entry>
 300               The bitmask of the regions that reported motion. There is at least one
 301               region. If this field is 0, then no motion was detected at all.
 302               If there is no <constant>V4L2_CID_DETECT_MD_REGION_GRID</constant> control
 303               (see <xref linkend="detect-controls" />) to assign a different region
 304               to each cell in the motion detection grid, then that all cells
 305               are automatically assigned to the default region 0.
 306             </entry>
 307           </row>
 308         </tbody>
 309       </tgroup>
 310     </table>
 311
 312     <table pgwide="1" frame="none" id="changes-flags">
 313       <title>Changes</title>
 314       <tgroup cols="3">
 315         &cs-def;
 316         <tbody valign="top">
 317           <row>
 318             <entry><constant>V4L2_EVENT_CTRL_CH_VALUE</constant></entry>
 319             <entry>0x0001</entry>
 320             <entry>This control event was triggered because the value of the control
 321                 changed. Special case: if a button control is pressed, then this
 322                 event is sent as well, even though there is not explicit value
 323                 associated with a button control.</entry>
 324           </row>
 325           <row>
 326             <entry><constant>V4L2_EVENT_CTRL_CH_FLAGS</constant></entry>
 327             <entry>0x0002</entry>
 328             <entry>This control event was triggered because the control flags
 329                 changed.</entry>
 330           </row>
 331           <row>
 332             <entry><constant>V4L2_EVENT_CTRL_CH_RANGE</constant></entry>
 333             <entry>0x0004</entry>
 334             <entry>This control event was triggered because the minimum,
 335             maximum, step or the default value of the control changed.</entry>
 336           </row>
 337         </tbody>
 338       </tgroup>
 339     </table>
 340
 341     <table pgwide="1" frame="none" id="src-changes-flags">
 342       <title>Source Changes</title>
 343       <tgroup cols="3">
 344         &cs-def;
 345         <tbody valign="top">
 346           <row>
 347             <entry><constant>V4L2_EVENT_SRC_CH_RESOLUTION</constant></entry>
 348             <entry>0x0001</entry>
 349             <entry>This event gets triggered when a resolution change is
 350             detected at an input. This can come from an input connector or
 351             from a video decoder.
 352             </entry>
 353           </row>
 354         </tbody>
 355       </tgroup>
 356     </table>
 357   </refsect1>
 358   <refsect1>
 359     &return-value;
 360   </refsect1>
 361 </refentry>