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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.</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.</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>
+    </variablelist>
+  </refsect1>
+</refentry>
+
+<!--
+Local Variables:
+mode: sgml
+sgml-parent-document: "v4l2.sgml"
+indent-tabs-mode: nil
+End:
+-->