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<refentry id="vidioc-g-ext-ctrls">
<refmeta>
<refentrytitle>ioctl VIDIOC_G_EXT_CTRLS, VIDIOC_S_EXT_CTRLS,
VIDIOC_TRY_EXT_CTRLS</refentrytitle>
&manvol;
</refmeta>
<refnamediv>
<refname>VIDIOC_G_EXT_CTRLS</refname>
<refname>VIDIOC_S_EXT_CTRLS</refname>
<refname>VIDIOC_TRY_EXT_CTRLS</refname>
<refpurpose>Get or set the value of several controls, try control
values</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_ext_controls
*<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_EXT_CTRLS, VIDIOC_S_EXT_CTRLS,
VIDIOC_TRY_EXT_CTRLS</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>argp</parameter></term>
<listitem>
<para></para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Description</title>
<para>These ioctls allow the caller to get or set multiple
controls atomically. Control IDs are grouped into control classes (see
<xref linkend="ctrl-class">) and all controls in the control array
must belong to the same control class.</para>
<para>Applications must always fill in the
<structfield>count</structfield>,
<structfield>ctrl_class</structfield>,
<structfield>controls</structfield> and
<structfield>reserved</structfield> fields of &v4l2-ext-controls;, and
initialize the &v4l2-ext-control; array pointed to by the
<structfield>controls</structfield> fields.</para>
<para>To get the current value of a set of controls applications
initialize the <structfield>id</structfield> field of each
&v4l2-ext-control; and call the
<constant>VIDIOC_G_EXT_CTRLS</constant> ioctl.</para>
<para>To change the value of a set of controls applications
initialize the <structfield>id</structfield> and
<structfield>value</structfield> fields of a &v4l2-ext-control; and
call the <constant>VIDIOC_S_EXT_CTRLS</constant> ioctl. The controls
will only be set if <emphasis>all</emphasis> control values are
valid.</para>
<para>To check if the a set of controls have correct values
applications initialize the <structfield>id</structfield> and
<structfield>value</structfield> fields of a &v4l2-ext-control; and
call the <constant>VIDIOC_TRY_EXT_CTRLS</constant> ioctl. It is up to
the driver whether wrong values are automatically adjusted to a valid
value or if an error is returned.</para>
<para>When the <structfield>id</structfield> or
<structfield>ctrl_class</structfield> is invalid drivers return an
&EINVAL;. When the value is out of bounds drivers can choose to take
the closest valid value or return an &ERANGE;, whatever seems more
appropriate. In the first case the new value is set in
&v4l2-ext-control;.</para>
<para>The driver will only set/get these controls if all control
values are correct. This prevents the situation where only some of the
controls were set/get. Only low-level errors (⪚ a failed i2c
command) can still cause this situation.</para>
<table pgwide="1" frame="none" id="v4l2-ext-control">
<title>struct <structname>v4l2_ext_control</structname></title>
<tgroup cols="4">
&cs-ustr;
<tbody valign="top">
<row>
<entry>__u32</entry>
<entry><structfield>id</structfield></entry>
<entry></entry>
<entry>Identifies the control, set by the
application.</entry>
</row>
<row>
<entry>__u32</entry>
<entry><structfield>reserved2</structfield>[2]</entry>
<entry></entry>
<entry>Reserved for future extensions. Drivers and
applications must set the array to zero.</entry>
</row>
<row>
<entry>union</entry>
<entry>(anonymous)</entry>
</row>
<row>
<entry></entry>
<entry>__s32</entry>
<entry><structfield>value</structfield></entry>
<entry>New value or current value.</entry>
</row>
<row>
<entry></entry>
<entry>__s64</entry>
<entry><structfield>value64</structfield></entry>
<entry>New value or current value.</entry>
</row>
<row>
<entry></entry>
<entry>void *</entry>
<entry><structfield>reserved</structfield></entry>
<entry>Reserved for future pointer-type controls. Currently unused.</entry>
</row>
</tbody>
</tgroup>
</table>
<table pgwide="1" frame="none" id="v4l2-ext-controls">
<title>struct <structname>v4l2_ext_controls</structname></title>
<tgroup cols="3">
&cs-str;
<tbody valign="top">
<row>
<entry>__u32</entry>
<entry><structfield>ctrl_class</structfield></entry>
<entry>The control class to which all controls belong, see
<xref linkend="ctrl-class">.</entry>
</row>
<row>
<entry>__u32</entry>
<entry><structfield>count</structfield></entry>
<entry>The number of controls in the controls array. May
also be zero.</entry>
</row>
<row>
<entry>__u32</entry>
<entry><structfield>error_idx</structfield></entry>
<entry>Set by the driver in case of an error. It is the
index of the control causing the error or equal to 'count' when the
error is not associated with a particular control. Undefined when the
ioctl returns 0 (success).</entry>
</row>
<row>
<entry>__u32</entry>
<entry><structfield>reserved</structfield>[2]</entry>
<entry>Reserved for future extensions. Drivers and
applications must set the array to zero.</entry>
</row>
<row>
<entry>&v4l2-ext-control; *</entry>
<entry><structfield>controls</structfield></entry>
<entry>Pointer to an array of
<structfield>count</structfield> v4l2_ext_control structures. Ignored
if <structfield>count</structfield> equals zero.</entry>
</row>
</tbody>
</tgroup>
</table>
<table pgwide="1" frame="none" id="ctrl-class">
<title>Control classes</title>
<tgroup cols="3">
&cs-def;
<tbody valign="top">
<row>
<entry><constant>V4L2_CTRL_CLASS_USER</constant></entry>
<entry>0x980000</entry>
<entry>The class containing user controls. These controls
are described in <xref linkend="control">. All controls that can be set
using the &VIDIOC-S-CTRL; and &VIDIOC-G-CTRL; ioctl belong to this
class.</entry>
</row>
<row>
<entry><constant>V4L2_CTRL_CLASS_MPEG</constant></entry>
<entry>0x990000</entry>
<entry>The class containing MPEG compression controls.
These controls are described in section <xref
linkend="mpeg-controls">.</entry>
</row>
</tbody>
</tgroup>
</table>
</refsect1>
<refsect1>
&return-value;
<variablelist>
<varlistentry>
<term><errorcode>EINVAL</errorcode></term>
<listitem>
<para>The &v4l2-ext-control; <structfield>id</structfield>
is invalid or the &v4l2-ext-controls;
<structfield>ctrl_class</structfield> is invalid. This error code is
also returned by the <constant>VIDIOC_S_EXT_CTRLS</constant> and
<constant>VIDIOC_TRY_EXT_CTRLS</constant> ioctls if two or more
control values are in conflict.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><errorcode>ERANGE</errorcode></term>
<listitem>
<para>The &v4l2-ext-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>
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