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Based on kernel version 4.0. Page generated on 2015-04-14 21:23 EST.

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>
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