Based on kernel version 3.0.4. Page generated on 2011-10-03 22:07 EST.
1 <refentry id="vidioc-g-ext-ctrls"> 2 <refmeta> 3 <refentrytitle>ioctl VIDIOC_G_EXT_CTRLS, VIDIOC_S_EXT_CTRLS, 4 VIDIOC_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 13 values</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, 42 VIDIOC_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 58 controls atomically. Control IDs are grouped into control classes (see 59 <xref linkend="ctrl-class" />) and all controls in the control array 60 must 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 67 initialize 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 71 initialize the <structfield>id</structfield>, 72 <structfield>size</structfield> and <structfield>reserved2</structfield> fields 73 of each &v4l2-ext-control; and call the 74 <constant>VIDIOC_G_EXT_CTRLS</constant> ioctl. String controls controls 75 must also set the <structfield>string</structfield> field.</para> 76 77 <para>If the <structfield>size</structfield> is too small to 78 receive the control result (only relevant for pointer-type controls 79 like strings), then the driver will set <structfield>size</structfield> 80 to a valid value and return an &ENOSPC;. You should re-allocate the 81 string memory to this new size and try again. It is possible that the 82 same issue occurs again if the string has grown in the meantime. It is 83 recommended to call &VIDIOC-QUERYCTRL; first and use 84 <structfield>maximum</structfield>+1 as the new <structfield>size</structfield> 85 value. It is guaranteed that that is sufficient memory. 86 </para> 87 88 <para>To change the value of a set of controls applications 89 initialize the <structfield>id</structfield>, <structfield>size</structfield>, 90 <structfield>reserved2</structfield> and 91 <structfield>value/string</structfield> fields of each &v4l2-ext-control; and 92 call the <constant>VIDIOC_S_EXT_CTRLS</constant> ioctl. The controls 93 will only be set if <emphasis>all</emphasis> control values are 94 valid.</para> 95 96 <para>To check if a set of controls have correct values applications 97 initialize the <structfield>id</structfield>, <structfield>size</structfield>, 98 <structfield>reserved2</structfield> and 99 <structfield>value/string</structfield> fields of each &v4l2-ext-control; and 100 call the <constant>VIDIOC_TRY_EXT_CTRLS</constant> ioctl. It is up to 101 the driver whether wrong values are automatically adjusted to a valid 102 value 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 107 the closest valid value or return an &ERANGE;, whatever seems more 108 appropriate. 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 112 values are correct. This prevents the situation where only some of the 113 controls were set/get. Only low-level errors (⪚ a failed i2c 114 command) 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 126 application.</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 133 control. This is normally 0, but for pointer controls this should be 134 set to the size of the memory containing the payload, or that will 135 receive the payload. If <constant>VIDIOC_G_EXT_CTRLS</constant> finds 136 that this value is less than is required to store 137 the payload result, then it is set to a value large enough to store the 138 payload result and ENOSPC is returned. Note that for string controls 139 this <structfield>size</structfield> field should not be confused with the length of the string. 140 This field refers to the size of the memory that contains the string. 141 The 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 149 applications 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 192 also 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 198 index of the control causing the error or equal to 'count' when the 199 error is not associated with a particular control. Undefined when the 200 ioctl 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 206 applications 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 213 if <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 228 are described in <xref linkend="control" />. All controls that can be set 229 using the &VIDIOC-S-CTRL; and &VIDIOC-G-CTRL; ioctl belong to this 230 class.</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. 236 These 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. 243 These 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. 250 These 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> 267 is invalid or the &v4l2-ext-controls; 268 <structfield>ctrl_class</structfield> is invalid. This error code is 269 also returned by the <constant>VIDIOC_S_EXT_CTRLS</constant> and 270 <constant>VIDIOC_TRY_EXT_CTRLS</constant> ioctls if two or more 271 control 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> 278 is 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 285 because another applications took over control of the device function 286 this 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. 293 The field <structfield>size</structfield> is set to a value that is enough 294 to store the payload and this error code is returned.</para> 295 </listitem> 296 </varlistentry> 297 </variablelist> 298 </refsect1> 299 </refentry> 300 301 <!-- 302 Local Variables: 303 mode: sgml 304 sgml-parent-document: "v4l2.sgml" 305 indent-tabs-mode: nil 306 End: 307 -->
