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1<refentry id="vidioc-g-ext-ctrls">
2 <refmeta>
3 <refentrytitle>ioctl VIDIOC_G_EXT_CTRLS, VIDIOC_S_EXT_CTRLS,
4VIDIOC_TRY_EXT_CTRLS</refentrytitle>
5 &manvol;
6 </refmeta>
7
8 <refnamediv>
9 <refname>VIDIOC_G_EXT_CTRLS</refname>
10 <refname>VIDIOC_S_EXT_CTRLS</refname>
11 <refname>VIDIOC_TRY_EXT_CTRLS</refname>
12 <refpurpose>Get or set the value of several controls, try control
13values</refpurpose>
14 </refnamediv>
15
16 <refsynopsisdiv>
17 <funcsynopsis>
18 <funcprototype>
19 <funcdef>int <function>ioctl</function></funcdef>
20 <paramdef>int <parameter>fd</parameter></paramdef>
21 <paramdef>int <parameter>request</parameter></paramdef>
22 <paramdef>struct v4l2_ext_controls
23*<parameter>argp</parameter></paramdef>
24 </funcprototype>
25 </funcsynopsis>
26 </refsynopsisdiv>
27
28 <refsect1>
29 <title>Arguments</title>
30
31 <variablelist>
32 <varlistentry>
33 <term><parameter>fd</parameter></term>
34 <listitem>
35 <para>&fd;</para>
36 </listitem>
37 </varlistentry>
38 <varlistentry>
39 <term><parameter>request</parameter></term>
40 <listitem>
41 <para>VIDIOC_G_EXT_CTRLS, VIDIOC_S_EXT_CTRLS,
42VIDIOC_TRY_EXT_CTRLS</para>
43 </listitem>
44 </varlistentry>
45 <varlistentry>
46 <term><parameter>argp</parameter></term>
47 <listitem>
48 <para></para>
49 </listitem>
50 </varlistentry>
51 </variablelist>
52 </refsect1>
53
54 <refsect1>
55 <title>Description</title>
56
57 <para>These ioctls allow the caller to get or set multiple
58controls atomically. Control IDs are grouped into control classes (see
59<xref linkend="ctrl-class" />) and all controls in the control array
60must belong to the same control class.</para>
61
62 <para>Applications must always fill in the
63<structfield>count</structfield>,
64<structfield>ctrl_class</structfield>,
65<structfield>controls</structfield> and
66<structfield>reserved</structfield> fields of &v4l2-ext-controls;, and
67initialize the &v4l2-ext-control; array pointed to by the
68<structfield>controls</structfield> fields.</para>
69
70 <para>To get the current value of a set of controls applications
71initialize the <structfield>id</structfield>,
72<structfield>size</structfield> and <structfield>reserved2</structfield> fields
73of each &v4l2-ext-control; and call the
74<constant>VIDIOC_G_EXT_CTRLS</constant> ioctl. String controls controls
75must also set the <structfield>string</structfield> field.</para>
76
77 <para>If the <structfield>size</structfield> is too small to
78receive the control result (only relevant for pointer-type controls
79like strings), then the driver will set <structfield>size</structfield>
80to a valid value and return an &ENOSPC;. You should re-allocate the
81string memory to this new size and try again. It is possible that the
82same issue occurs again if the string has grown in the meantime. It is
83recommended to call &VIDIOC-QUERYCTRL; first and use
84<structfield>maximum</structfield>+1 as the new <structfield>size</structfield>
85value. It is guaranteed that that is sufficient memory.
86</para>
87
88 <para>To change the value of a set of controls applications
89initialize the <structfield>id</structfield>, <structfield>size</structfield>,
90<structfield>reserved2</structfield> and
91<structfield>value/string</structfield> fields of each &v4l2-ext-control; and
92call the <constant>VIDIOC_S_EXT_CTRLS</constant> ioctl. The controls
93will only be set if <emphasis>all</emphasis> control values are
94valid.</para>
95
96 <para>To check if a set of controls have correct values applications
97initialize the <structfield>id</structfield>, <structfield>size</structfield>,
98<structfield>reserved2</structfield> and
99<structfield>value/string</structfield> fields of each &v4l2-ext-control; and
100call the <constant>VIDIOC_TRY_EXT_CTRLS</constant> ioctl. It is up to
101the driver whether wrong values are automatically adjusted to a valid
102value or if an error is returned.</para>
103
104 <para>When the <structfield>id</structfield> or
105<structfield>ctrl_class</structfield> is invalid drivers return an
106&EINVAL;. When the value is out of bounds drivers can choose to take
107the closest valid value or return an &ERANGE;, whatever seems more
108appropriate. In the first case the new value is set in
109&v4l2-ext-control;.</para>
110
111 <para>The driver will only set/get these controls if all control
112values are correct. This prevents the situation where only some of the
113controls were set/get. Only low-level errors (&eg; a failed i2c
114command) can still cause this situation.</para>
115
116 <table pgwide="1" frame="none" id="v4l2-ext-control">
117 <title>struct <structname>v4l2_ext_control</structname></title>
118 <tgroup cols="4">
119 &cs-ustr;
120 <tbody valign="top">
121 <row>
122 <entry>__u32</entry>
123 <entry><structfield>id</structfield></entry>
124 <entry></entry>
125 <entry>Identifies the control, set by the
126application.</entry>
127 </row>
128 <row>
129 <entry>__u32</entry>
130 <entry><structfield>size</structfield></entry>
131 <entry></entry>
132 <entry>The total size in bytes of the payload of this
133control. This is normally 0, but for pointer controls this should be
134set to the size of the memory containing the payload, or that will
135receive the payload. If <constant>VIDIOC_G_EXT_CTRLS</constant> finds
136that this value is less than is required to store
137the payload result, then it is set to a value large enough to store the
138payload result and ENOSPC is returned. Note that for string controls
139this <structfield>size</structfield> field should not be confused with the length of the string.
140This field refers to the size of the memory that contains the string.
141The actual <emphasis>length</emphasis> of the string may well be much smaller.
142</entry>
143 </row>
144 <row>
145 <entry>__u32</entry>
146 <entry><structfield>reserved2</structfield>[1]</entry>
147 <entry></entry>
148 <entry>Reserved for future extensions. Drivers and
149applications must set the array to zero.</entry>
150 </row>
151 <row>
152 <entry>union</entry>
153 <entry>(anonymous)</entry>
154 </row>
155 <row>
156 <entry></entry>
157 <entry>__s32</entry>
158 <entry><structfield>value</structfield></entry>
159 <entry>New value or current value.</entry>
160 </row>
161 <row>
162 <entry></entry>
163 <entry>__s64</entry>
164 <entry><structfield>value64</structfield></entry>
165 <entry>New value or current value.</entry>
166 </row>
167 <row>
168 <entry></entry>
169 <entry>char *</entry>
170 <entry><structfield>string</structfield></entry>
171 <entry>A pointer to a string.</entry>
172 </row>
173 </tbody>
174 </tgroup>
175 </table>
176
177 <table pgwide="1" frame="none" id="v4l2-ext-controls">
178 <title>struct <structname>v4l2_ext_controls</structname></title>
179 <tgroup cols="3">
180 &cs-str;
181 <tbody valign="top">
182 <row>
183 <entry>__u32</entry>
184 <entry><structfield>ctrl_class</structfield></entry>
185 <entry>The control class to which all controls belong, see
186<xref linkend="ctrl-class" />.</entry>
187 </row>
188 <row>
189 <entry>__u32</entry>
190 <entry><structfield>count</structfield></entry>
191 <entry>The number of controls in the controls array. May
192also be zero.</entry>
193 </row>
194 <row>
195 <entry>__u32</entry>
196 <entry><structfield>error_idx</structfield></entry>
197 <entry>Set by the driver in case of an error. It is the
198index of the control causing the error or equal to 'count' when the
199error is not associated with a particular control. Undefined when the
200ioctl returns 0 (success).</entry>
201 </row>
202 <row>
203 <entry>__u32</entry>
204 <entry><structfield>reserved</structfield>[2]</entry>
205 <entry>Reserved for future extensions. Drivers and
206applications must set the array to zero.</entry>
207 </row>
208 <row>
209 <entry>&v4l2-ext-control; *</entry>
210 <entry><structfield>controls</structfield></entry>
211 <entry>Pointer to an array of
212<structfield>count</structfield> v4l2_ext_control structures. Ignored
213if <structfield>count</structfield> equals zero.</entry>
214 </row>
215 </tbody>
216 </tgroup>
217 </table>
218
219 <table pgwide="1" frame="none" id="ctrl-class">
220 <title>Control classes</title>
221 <tgroup cols="3">
222 &cs-def;
223 <tbody valign="top">
224 <row>
225 <entry><constant>V4L2_CTRL_CLASS_USER</constant></entry>
226 <entry>0x980000</entry>
227 <entry>The class containing user controls. These controls
228are described in <xref linkend="control" />. All controls that can be set
229using the &VIDIOC-S-CTRL; and &VIDIOC-G-CTRL; ioctl belong to this
230class.</entry>
231 </row>
232 <row>
233 <entry><constant>V4L2_CTRL_CLASS_MPEG</constant></entry>
234 <entry>0x990000</entry>
235 <entry>The class containing MPEG compression controls.
236These controls are described in <xref
237 linkend="mpeg-controls" />.</entry>
238 </row>
239 <row>
240 <entry><constant>V4L2_CTRL_CLASS_CAMERA</constant></entry>
241 <entry>0x9a0000</entry>
242 <entry>The class containing camera controls.
243These controls are described in <xref
244 linkend="camera-controls" />.</entry>
245 </row>
246 <row>
247 <entry><constant>V4L2_CTRL_CLASS_FM_TX</constant></entry>
248 <entry>0x9b0000</entry>
249 <entry>The class containing FM Transmitter (FM TX) controls.
250These controls are described in <xref
251 linkend="fm-tx-controls" />.</entry>
252 </row>
253 </tbody>
254 </tgroup>
255 </table>
256
257 </refsect1>
258
259 <refsect1>
260 &return-value;
261
262 <variablelist>
263 <varlistentry>
264 <term><errorcode>EINVAL</errorcode></term>
265 <listitem>
266 <para>The &v4l2-ext-control; <structfield>id</structfield>
267is invalid or the &v4l2-ext-controls;
268<structfield>ctrl_class</structfield> is invalid. This error code is
269also returned by the <constant>VIDIOC_S_EXT_CTRLS</constant> and
270<constant>VIDIOC_TRY_EXT_CTRLS</constant> ioctls if two or more
271control values are in conflict.</para>
272 </listitem>
273 </varlistentry>
274 <varlistentry>
275 <term><errorcode>ERANGE</errorcode></term>
276 <listitem>
277 <para>The &v4l2-ext-control; <structfield>value</structfield>
278is out of bounds.</para>
279 </listitem>
280 </varlistentry>
281 <varlistentry>
282 <term><errorcode>EBUSY</errorcode></term>
283 <listitem>
284 <para>The control is temporarily not changeable, possibly
285because another applications took over control of the device function
286this control belongs to.</para>
287 </listitem>
288 </varlistentry>
289 <varlistentry>
290 <term><errorcode>ENOSPC</errorcode></term>
291 <listitem>
292 <para>The space reserved for the control's payload is insufficient.
293The field <structfield>size</structfield> is set to a value that is enough
294to store the payload and this error code is returned.</para>
295 </listitem>
296 </varlistentry>
297 </variablelist>
298 </refsect1>
299</refentry>
300
301<!--
302Local Variables:
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304sgml-parent-document: "v4l2.sgml"
305indent-tabs-mode: nil
306End:
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