Based on kernel version 4.7.2. Page generated on 2016-08-22 22:45 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. If the <structfield>value</structfield> 68 is inappropriate for the control (e.g. if it refers to an unsupported 69 menu index of a menu control), then &EINVAL; is returned as well.</para> 70 71 <para>These ioctls work only with user controls. For other 72 control classes the &VIDIOC-G-EXT-CTRLS;, &VIDIOC-S-EXT-CTRLS; or 73 &VIDIOC-TRY-EXT-CTRLS; must be used.</para> 74 75 <table pgwide="1" frame="none" id="v4l2-control"> 76 <title>struct <structname>v4l2_control</structname></title> 77 <tgroup cols="3"> 78 &cs-str; 79 <tbody valign="top"> 80 <row> 81 <entry>__u32</entry> 82 <entry><structfield>id</structfield></entry> 83 <entry>Identifies the control, set by the 84 application.</entry> 85 </row> 86 <row> 87 <entry>__s32</entry> 88 <entry><structfield>value</structfield></entry> 89 <entry>New value or current value.</entry> 90 </row> 91 </tbody> 92 </tgroup> 93 </table> 94 </refsect1> 95 96 <refsect1> 97 &return-value; 98 99 <variablelist> 100 <varlistentry> 101 <term><errorcode>EINVAL</errorcode></term> 102 <listitem> 103 <para>The &v4l2-control; <structfield>id</structfield> is 104 invalid or the <structfield>value</structfield> is inappropriate for 105 the given control (i.e. if a menu item is selected that is not supported 106 by the driver according to &VIDIOC-QUERYMENU;).</para> 107 </listitem> 108 </varlistentry> 109 <varlistentry> 110 <term><errorcode>ERANGE</errorcode></term> 111 <listitem> 112 <para>The &v4l2-control; <structfield>value</structfield> 113 is out of bounds.</para> 114 </listitem> 115 </varlistentry> 116 <varlistentry> 117 <term><errorcode>EBUSY</errorcode></term> 118 <listitem> 119 <para>The control is temporarily not changeable, possibly 120 because another applications took over control of the device function 121 this control belongs to.</para> 122 </listitem> 123 </varlistentry> 124 <varlistentry> 125 <term><errorcode>EACCES</errorcode></term> 126 <listitem> 127 <para>Attempt to set a read-only control or to get a 128 write-only control.</para> 129 </listitem> 130 </varlistentry> 131 </variablelist> 132 </refsect1> 133 </refentry>
