aboutsummaryrefslogtreecommitdiffstats
path: root/Documentation/DocBook/media/v4l/vidioc-dqevent.xml
blob: 5200b6874654d0816b35fa0f260d49720ebd25af (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
<refentry id="vidioc-dqevent">
  <refmeta>
    <refentrytitle>ioctl VIDIOC_DQEVENT</refentrytitle>
    &manvol;
  </refmeta>

  <refnamediv>
    <refname>VIDIOC_DQEVENT</refname>
    <refpurpose>Dequeue event</refpurpose>
  </refnamediv>

  <refsynopsisdiv>
    <funcsynopsis>
      <funcprototype>
	<funcdef>int <function>ioctl</function></funcdef>
	<paramdef>int <parameter>fd</parameter></paramdef>
	<paramdef>int <parameter>request</parameter></paramdef>
	<paramdef>struct v4l2_event
*<parameter>argp</parameter></paramdef>
      </funcprototype>
    </funcsynopsis>
  </refsynopsisdiv>

  <refsect1>
    <title>Arguments</title>

    <variablelist>
      <varlistentry>
	<term><parameter>fd</parameter></term>
	<listitem>
	  <para>&fd;</para>
	</listitem>
      </varlistentry>
      <varlistentry>
	<term><parameter>request</parameter></term>
	<listitem>
	  <para>VIDIOC_DQEVENT</para>
	</listitem>
      </varlistentry>
      <varlistentry>
	<term><parameter>argp</parameter></term>
	<listitem>
	  <para></para>
	</listitem>
      </varlistentry>
    </variablelist>
  </refsect1>

  <refsect1>
    <title>Description</title>

    <para>Dequeue an event from a video device. No input is required
    for this ioctl. All the fields of the &v4l2-event; structure are
    filled by the driver. The file handle will also receive exceptions
    which the application may get by e.g. using the select system
    call.</para>

    <table frame="none" pgwide="1" id="v4l2-event">
      <title>struct <structname>v4l2_event</structname></title>
      <tgroup cols="4">
	&cs-str;
	<tbody valign="top">
	  <row>
	    <entry>__u32</entry>
	    <entry><structfield>type</structfield></entry>
            <entry></entry>
	    <entry>Type of the event.</entry>
	  </row>
	  <row>
	    <entry>union</entry>
	    <entry><structfield>u</structfield></entry>
            <entry></entry>
	    <entry></entry>
	  </row>
	  <row>
	    <entry></entry>
	    <entry>&v4l2-event-vsync;</entry>
            <entry><structfield>vsync</structfield></entry>
	    <entry>Event data for event V4L2_EVENT_VSYNC.
            </entry>
	  </row>
	  <row>
	    <entry></entry>
	    <entry>&v4l2-event-ctrl;</entry>
            <entry><structfield>ctrl</structfield></entry>
	    <entry>Event data for event V4L2_EVENT_CTRL.
            </entry>
	  </row>
	  <row>
	    <entry></entry>
	    <entry>__u8</entry>
            <entry><structfield>data</structfield>[64]</entry>
	    <entry>Event data. Defined by the event type. The union
            should be used to define easily accessible type for
            events.</entry>
	  </row>
	  <row>
	    <entry>__u32</entry>
	    <entry><structfield>pending</structfield></entry>
            <entry></entry>
	    <entry>Number of pending events excluding this one.</entry>
	  </row>
	  <row>
	    <entry>__u32</entry>
	    <entry><structfield>sequence</structfield></entry>
            <entry></entry>
	    <entry>Event sequence number. The sequence number is
	    incremented for every subscribed event that takes place.
	    If sequence numbers are not contiguous it means that
	    events have been lost.
	    </entry>
	  </row>
	  <row>
	    <entry>struct timespec</entry>
	    <entry><structfield>timestamp</structfield></entry>
            <entry></entry>
	    <entry>Event timestamp.</entry>
	  </row>
	  <row>
	    <entry>u32</entry>
	    <entry><structfield>id</structfield></entry>
            <entry></entry>
	    <entry>The ID associated with the event source. If the event does not
		have an associated ID (this depends on the event type), then this
		is 0.</entry>
	  </row>
	  <row>
	    <entry>__u32</entry>
	    <entry><structfield>reserved</structfield>[8]</entry>
            <entry></entry>
	    <entry>Reserved for future extensions. Drivers must set
	    the array to zero.</entry>
	  </row>
	</tbody>
      </tgroup>
    </table>

    <table frame="none" pgwide="1" id="v4l2-event-vsync">
      <title>struct <structname>v4l2_event_vsync</structname></title>
      <tgroup cols="3">
	&cs-str;
	<tbody valign="top">
	  <row>
	    <entry>__u8</entry>
	    <entry><structfield>field</structfield></entry>
	    <entry>The upcoming field. See &v4l2-field;.</entry>
	  </row>
	</tbody>
      </tgroup>
    </table>

    <table frame="none" pgwide="1" id="v4l2-event-ctrl">
      <title>struct <structname>v4l2_event_ctrl</structname></title>
      <tgroup cols="4">
	&cs-str;
	<tbody valign="top">
	  <row>
	    <entry>__u32</entry>
	    <entry><structfield>changes</structfield></entry>
	    <entry></entry>
	    <entry>A bitmask that tells what has changed. See <xref linkend="changes-flags" />.</entry>
	  </row>
	  <row>
	    <entry>__u32</entry>
	    <entry><structfield>type</structfield></entry>
	    <entry></entry>
	    <entry>The type of the control. See &v4l2-ctrl-type;.</entry>
	  </row>
	  <row>
	    <entry>union (anonymous)</entry>
	    <entry></entry>
	    <entry></entry>
	    <entry></entry>
	  </row>
	  <row>
	    <entry></entry>
	    <entry>__s32</entry>
	    <entry><structfield>value</structfield></entry>
	    <entry>The 32-bit value of the control for 32-bit control types.
		This is 0 for string controls since the value of a string
		cannot be passed using &VIDIOC-DQEVENT;.</entry>
	  </row>
	  <row>
	    <entry></entry>
	    <entry>__s64</entry>
	    <entry><structfield>value64</structfield></entry>
	    <entry>The 64-bit value of the control for 64-bit control types.</entry>
	  </row>
	  <row>
	    <entry>__u32</entry>
	    <entry><structfield>flags</structfield></entry>
	    <entry></entry>
	    <entry>The control flags. See <xref linkend="control-flags" />.</entry>
	  </row>
	  <row>
	    <entry>__s32</entry>
	    <entry><structfield>minimum</structfield></entry>
	    <entry></entry>
	    <entry>The minimum value of the control. See &v4l2-queryctrl;.</entry>
	  </row>
	  <row>
	    <entry>__s32</entry>
	    <entry><structfield>maximum</structfield></entry>
	    <entry></entry>
	    <entry>The maximum value of the control. See &v4l2-queryctrl;.</entry>
	  </row>
	  <row>
	    <entry>__s32</entry>
	    <entry><structfield>step</structfield></entry>
	    <entry></entry>
	    <entry>The step value of the control. See &v4l2-queryctrl;.</entry>
	  </row>
	  <row>
	    <entry>__s32</entry>
	    <entry><structfield>default_value</structfield></entry>
	    <entry></entry>
	    <entry>The default value value of the control. See &v4l2-queryctrl;.</entry>
	  </row>
	</tbody>
      </tgroup>
    </table>

    <table pgwide="1" frame="none" id="changes-flags">
      <title>Changes</title>
      <tgroup cols="3">
	&cs-def;
	<tbody valign="top">
	  <row>
	    <entry><constant>V4L2_EVENT_CTRL_CH_VALUE</constant></entry>
	    <entry>0x0001</entry>
	    <entry>This control event was triggered because the value of the control
		changed. Special case: if a button control is pressed, then this
		event is sent as well, even though there is not explicit value
		associated with a button control.</entry>
	  </row>
	  <row>
	    <entry><constant>V4L2_EVENT_CTRL_CH_FLAGS</constant></entry>
	    <entry>0x0002</entry>
	    <entry>This control event was triggered because the control flags
		changed.</entry>
	  </row>
	</tbody>
      </tgroup>
    </table>
  </refsect1>
  <refsect1>
    &return-value;
  </refsect1>
</refentry>