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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
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