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+<refentry id="vidioc-g-ctrl">
+ <refmeta>
+ <refentrytitle>ioctl VIDIOC_G_CTRL, VIDIOC_S_CTRL</refentrytitle>
+ &manvol;
+ </refmeta>
+
+ <refnamediv>
+ <refname>VIDIOC_G_CTRL</refname>
+ <refname>VIDIOC_S_CTRL</refname>
+ <refpurpose>Get or set the value of a control</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_control
+*<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_G_CTRL, VIDIOC_S_CTRL</para>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term><parameter>argp</parameter></term>
+ <listitem>
+ <para></para>
+ </listitem>
+ </varlistentry>
+ </variablelist>
+ </refsect1>
+
+ <refsect1>
+ <title>Description</title>
+
+ <para>To get the current value of a control applications
+initialize the <structfield>id</structfield> field of a struct
+<structname>v4l2_control</structname> and call the
+<constant>VIDIOC_G_CTRL</constant> ioctl with a pointer to this
+structure. To change the value of a control applications initialize
+the <structfield>id</structfield> and <structfield>value</structfield>
+fields of a struct <structname>v4l2_control</structname> and call the
+<constant>VIDIOC_S_CTRL</constant> ioctl.</para>
+
+ <para>When the <structfield>id</structfield> is invalid drivers
+return an &EINVAL;. When the <structfield>value</structfield> is out
+of bounds drivers can choose to take the closest valid value or return
+an &ERANGE;, whatever seems more appropriate. However,
+<constant>VIDIOC_S_CTRL</constant> is a write-only ioctl, it does not
+return the actual new value. If the <structfield>value</structfield>
+is inappropriate for the control (e.g. if it refers to an unsupported
+menu index of a menu control), then &EINVAL; is returned as well.</para>
+
+ <para>These ioctls work only with user controls. For other
+control classes the &VIDIOC-G-EXT-CTRLS;, &VIDIOC-S-EXT-CTRLS; or
+&VIDIOC-TRY-EXT-CTRLS; must be used.</para>
+
+ <table pgwide="1" frame="none" id="v4l2-control">
+ <title>struct <structname>v4l2_control</structname></title>
+ <tgroup cols="3">
+ &cs-str;
+ <tbody valign="top">
+ <row>
+ <entry>__u32</entry>
+ <entry><structfield>id</structfield></entry>
+ <entry>Identifies the control, set by the
+application.</entry>
+ </row>
+ <row>
+ <entry>__s32</entry>
+ <entry><structfield>value</structfield></entry>
+ <entry>New value or current value.</entry>
+ </row>
+ </tbody>
+ </tgroup>
+ </table>
+ </refsect1>
+
+ <refsect1>
+ &return-value;
+
+ <variablelist>
+ <varlistentry>
+ <term><errorcode>EINVAL</errorcode></term>
+ <listitem>
+ <para>The &v4l2-control; <structfield>id</structfield> is
+invalid or the <structfield>value</structfield> is inappropriate for
+the given control (i.e. if a menu item is selected that is not supported
+by the driver according to &VIDIOC-QUERYMENU;).</para>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term><errorcode>ERANGE</errorcode></term>
+ <listitem>
+ <para>The &v4l2-control; <structfield>value</structfield>
+is out of bounds.</para>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term><errorcode>EBUSY</errorcode></term>
+ <listitem>
+ <para>The control is temporarily not changeable, possibly
+because another applications took over control of the device function
+this control belongs to.</para>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term><errorcode>EACCES</errorcode></term>
+ <listitem>
+ <para>Attempt to set a read-only control or to get a
+ write-only control.</para>
+ </listitem>
+ </varlistentry>
+ </variablelist>
+ </refsect1>
+</refentry>