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dd966083 SA |
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> | |
0e1de38d HV |
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> | |
85724983 HV |
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> | |
eab00a0d SA |
89 | <row> |
90 | <entry></entry> | |
91 | <entry>&v4l2-event-frame-sync;</entry> | |
2bece307 | 92 | <entry><structfield>frame_sync</structfield></entry> |
eab00a0d SA |
93 | <entry>Event data for event V4L2_EVENT_FRAME_SYNC.</entry> |
94 | </row> | |
dd966083 SA |
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> | |
0e1de38d | 120 | <entry>struct timespec</entry> |
dd966083 SA |
121 | <entry><structfield>timestamp</structfield></entry> |
122 | <entry></entry> | |
123 | <entry>Event timestamp.</entry> | |
124 | </row> | |
85724983 HV |
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> | |
dd966083 SA |
133 | <row> |
134 | <entry>__u32</entry> | |
85724983 | 135 | <entry><structfield>reserved</structfield>[8]</entry> |
dd966083 SA |
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 | ||
ffd638e0 SA |
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 | ||
eab00a0d SA |
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 | ||
ffd638e0 SA |
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 | </tbody> | |
265 | </tgroup> | |
266 | </table> | |
dd966083 | 267 | </refsect1> |
43c1daa4 MCC |
268 | <refsect1> |
269 | &return-value; | |
270 | </refsect1> | |
dd966083 | 271 | </refentry> |