About Kernel Documentation Linux Kernel Contact Linux Resources Linux Blog

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




Custom Search

Based on kernel version 3.13. Page generated on 2014-01-20 22:02 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 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>&v4l2-event-frame-sync;</entry>
92	            <entry><structfield>frame_sync</structfield></entry>
93		    <entry>Event data for event V4L2_EVENT_FRAME_SYNC.</entry>
94		  </row>
95		  <row>
96		    <entry></entry>
97		    <entry>__u8</entry>
98	            <entry><structfield>data</structfield>[64]</entry>
99		    <entry>Event data. Defined by the event type. The union
100	            should be used to define easily accessible type for
101	            events.</entry>
102		  </row>
103		  <row>
104		    <entry>__u32</entry>
105		    <entry><structfield>pending</structfield></entry>
106	            <entry></entry>
107		    <entry>Number of pending events excluding this one.</entry>
108		  </row>
109		  <row>
110		    <entry>__u32</entry>
111		    <entry><structfield>sequence</structfield></entry>
112	            <entry></entry>
113		    <entry>Event sequence number. The sequence number is
114		    incremented for every subscribed event that takes place.
115		    If sequence numbers are not contiguous it means that
116		    events have been lost.
117		    </entry>
118		  </row>
119		  <row>
120		    <entry>struct timespec</entry>
121		    <entry><structfield>timestamp</structfield></entry>
122	            <entry></entry>
123		    <entry>Event timestamp.</entry>
124		  </row>
125		  <row>
126		    <entry>u32</entry>
127		    <entry><structfield>id</structfield></entry>
128	            <entry></entry>
129		    <entry>The ID associated with the event source. If the event does not
130			have an associated ID (this depends on the event type), then this
131			is 0.</entry>
132		  </row>
133		  <row>
134		    <entry>__u32</entry>
135		    <entry><structfield>reserved</structfield>[8]</entry>
136	            <entry></entry>
137		    <entry>Reserved for future extensions. Drivers must set
138		    the array to zero.</entry>
139		  </row>
140		</tbody>
141	      </tgroup>
142	    </table>
143	
144	    <table frame="none" pgwide="1" id="v4l2-event-vsync">
145	      <title>struct <structname>v4l2_event_vsync</structname></title>
146	      <tgroup cols="3">
147		&cs-str;
148		<tbody valign="top">
149		  <row>
150		    <entry>__u8</entry>
151		    <entry><structfield>field</structfield></entry>
152		    <entry>The upcoming field. See &v4l2-field;.</entry>
153		  </row>
154		</tbody>
155	      </tgroup>
156	    </table>
157	
158	    <table frame="none" pgwide="1" id="v4l2-event-ctrl">
159	      <title>struct <structname>v4l2_event_ctrl</structname></title>
160	      <tgroup cols="4">
161		&cs-str;
162		<tbody valign="top">
163		  <row>
164		    <entry>__u32</entry>
165		    <entry><structfield>changes</structfield></entry>
166		    <entry></entry>
167		    <entry>A bitmask that tells what has changed. See <xref linkend="changes-flags" />.</entry>
168		  </row>
169		  <row>
170		    <entry>__u32</entry>
171		    <entry><structfield>type</structfield></entry>
172		    <entry></entry>
173		    <entry>The type of the control. See &v4l2-ctrl-type;.</entry>
174		  </row>
175		  <row>
176		    <entry>union (anonymous)</entry>
177		    <entry></entry>
178		    <entry></entry>
179		    <entry></entry>
180		  </row>
181		  <row>
182		    <entry></entry>
183		    <entry>__s32</entry>
184		    <entry><structfield>value</structfield></entry>
185		    <entry>The 32-bit value of the control for 32-bit control types.
186			This is 0 for string controls since the value of a string
187			cannot be passed using &VIDIOC-DQEVENT;.</entry>
188		  </row>
189		  <row>
190		    <entry></entry>
191		    <entry>__s64</entry>
192		    <entry><structfield>value64</structfield></entry>
193		    <entry>The 64-bit value of the control for 64-bit control types.</entry>
194		  </row>
195		  <row>
196		    <entry>__u32</entry>
197		    <entry><structfield>flags</structfield></entry>
198		    <entry></entry>
199		    <entry>The control flags. See <xref linkend="control-flags" />.</entry>
200		  </row>
201		  <row>
202		    <entry>__s32</entry>
203		    <entry><structfield>minimum</structfield></entry>
204		    <entry></entry>
205		    <entry>The minimum value of the control. See &v4l2-queryctrl;.</entry>
206		  </row>
207		  <row>
208		    <entry>__s32</entry>
209		    <entry><structfield>maximum</structfield></entry>
210		    <entry></entry>
211		    <entry>The maximum value of the control. See &v4l2-queryctrl;.</entry>
212		  </row>
213		  <row>
214		    <entry>__s32</entry>
215		    <entry><structfield>step</structfield></entry>
216		    <entry></entry>
217		    <entry>The step value of the control. See &v4l2-queryctrl;.</entry>
218		  </row>
219		  <row>
220		    <entry>__s32</entry>
221		    <entry><structfield>default_value</structfield></entry>
222		    <entry></entry>
223		    <entry>The default value value of the control. See &v4l2-queryctrl;.</entry>
224		  </row>
225		</tbody>
226	      </tgroup>
227	    </table>
228	
229	    <table frame="none" pgwide="1" id="v4l2-event-frame-sync">
230	      <title>struct <structname>v4l2_event_frame_sync</structname></title>
231	      <tgroup cols="3">
232		&cs-str;
233		<tbody valign="top">
234		  <row>
235		    <entry>__u32</entry>
236		    <entry><structfield>frame_sequence</structfield></entry>
237		    <entry>
238		      The sequence number of the frame being received.
239		    </entry>
240		  </row>
241		</tbody>
242	      </tgroup>
243	    </table>
244	
245	    <table pgwide="1" frame="none" id="changes-flags">
246	      <title>Changes</title>
247	      <tgroup cols="3">
248		&cs-def;
249		<tbody valign="top">
250		  <row>
251		    <entry><constant>V4L2_EVENT_CTRL_CH_VALUE</constant></entry>
252		    <entry>0x0001</entry>
253		    <entry>This control event was triggered because the value of the control
254			changed. Special case: if a button control is pressed, then this
255			event is sent as well, even though there is not explicit value
256			associated with a button control.</entry>
257		  </row>
258		  <row>
259		    <entry><constant>V4L2_EVENT_CTRL_CH_FLAGS</constant></entry>
260		    <entry>0x0002</entry>
261		    <entry>This control event was triggered because the control flags
262			changed.</entry>
263		  </row>
264		  <row>
265		    <entry><constant>V4L2_EVENT_CTRL_CH_RANGE</constant></entry>
266		    <entry>0x0004</entry>
267		    <entry>This control event was triggered because the minimum,
268		    maximum, step or the default value of the control changed.</entry>
269		  </row>
270		</tbody>
271	      </tgroup>
272	    </table>
273	  </refsect1>
274	  <refsect1>
275	    &return-value;
276	  </refsect1>
277	</refentry>
Hide Line Numbers
About Kernel Documentation Linux Kernel Contact Linux Resources Linux Blog

Information is copyright its respective author. All material is available from the Linux Kernel Source distributed under a GPL License. This page is provided as a free service by mjmwired.net.