131 lines
3.6 KiB
XML
131 lines
3.6 KiB
XML
<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:
|
|
-->
|