Based on kernel version 3.0.4. Page generated on 2011-10-03 22:07 EST.
1 <refentry id="vidioc-g-ctrl"> 2 <refmeta> 3 <refentrytitle>ioctl VIDIOC_G_CTRL, VIDIOC_S_CTRL</refentrytitle> 4 &manvol; 5 </refmeta> 6 7 <refnamediv> 8 <refname>VIDIOC_G_CTRL</refname> 9 <refname>VIDIOC_S_CTRL</refname> 10 <refpurpose>Get or set the value of a control</refpurpose> 11 </refnamediv> 12 13 <refsynopsisdiv> 14 <funcsynopsis> 15 <funcprototype> 16 <funcdef>int <function>ioctl</function></funcdef> 17 <paramdef>int <parameter>fd</parameter></paramdef> 18 <paramdef>int <parameter>request</parameter></paramdef> 19 <paramdef>struct v4l2_control 20 *<parameter>argp</parameter></paramdef> 21 </funcprototype> 22 </funcsynopsis> 23 </refsynopsisdiv> 24 25 <refsect1> 26 <title>Arguments</title> 27 28 <variablelist> 29 <varlistentry> 30 <term><parameter>fd</parameter></term> 31 <listitem> 32 <para>&fd;</para> 33 </listitem> 34 </varlistentry> 35 <varlistentry> 36 <term><parameter>request</parameter></term> 37 <listitem> 38 <para>VIDIOC_G_CTRL, VIDIOC_S_CTRL</para> 39 </listitem> 40 </varlistentry> 41 <varlistentry> 42 <term><parameter>argp</parameter></term> 43 <listitem> 44 <para></para> 45 </listitem> 46 </varlistentry> 47 </variablelist> 48 </refsect1> 49 50 <refsect1> 51 <title>Description</title> 52 53 <para>To get the current value of a control applications 54 initialize the <structfield>id</structfield> field of a struct 55 <structname>v4l2_control</structname> and call the 56 <constant>VIDIOC_G_CTRL</constant> ioctl with a pointer to this 57 structure. To change the value of a control applications initialize 58 the <structfield>id</structfield> and <structfield>value</structfield> 59 fields of a struct <structname>v4l2_control</structname> and call the 60 <constant>VIDIOC_S_CTRL</constant> ioctl.</para> 61 62 <para>When the <structfield>id</structfield> is invalid drivers 63 return an &EINVAL;. When the <structfield>value</structfield> is out 64 of bounds drivers can choose to take the closest valid value or return 65 an &ERANGE;, whatever seems more appropriate. However, 66 <constant>VIDIOC_S_CTRL</constant> is a write-only ioctl, it does not 67 return the actual new value.</para> 68 69 <para>These ioctls work only with user controls. For other 70 control classes the &VIDIOC-G-EXT-CTRLS;, &VIDIOC-S-EXT-CTRLS; or 71 &VIDIOC-TRY-EXT-CTRLS; must be used.</para> 72 73 <table pgwide="1" frame="none" id="v4l2-control"> 74 <title>struct <structname>v4l2_control</structname></title> 75 <tgroup cols="3"> 76 &cs-str; 77 <tbody valign="top"> 78 <row> 79 <entry>__u32</entry> 80 <entry><structfield>id</structfield></entry> 81 <entry>Identifies the control, set by the 82 application.</entry> 83 </row> 84 <row> 85 <entry>__s32</entry> 86 <entry><structfield>value</structfield></entry> 87 <entry>New value or current value.</entry> 88 </row> 89 </tbody> 90 </tgroup> 91 </table> 92 </refsect1> 93 94 <refsect1> 95 &return-value; 96 97 <variablelist> 98 <varlistentry> 99 <term><errorcode>EINVAL</errorcode></term> 100 <listitem> 101 <para>The &v4l2-control; <structfield>id</structfield> is 102 invalid.</para> 103 </listitem> 104 </varlistentry> 105 <varlistentry> 106 <term><errorcode>ERANGE</errorcode></term> 107 <listitem> 108 <para>The &v4l2-control; <structfield>value</structfield> 109 is out of bounds.</para> 110 </listitem> 111 </varlistentry> 112 <varlistentry> 113 <term><errorcode>EBUSY</errorcode></term> 114 <listitem> 115 <para>The control is temporarily not changeable, possibly 116 because another applications took over control of the device function 117 this control belongs to.</para> 118 </listitem> 119 </varlistentry> 120 </variablelist> 121 </refsect1> 122 </refentry> 123 124 <!-- 125 Local Variables: 126 mode: sgml 127 sgml-parent-document: "v4l2.sgml" 128 indent-tabs-mode: nil 129 End: 130 -->
