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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>,
-<structfield>size</structfield> and <structfield>reserved2</structfield> fields
-of each &v4l2-ext-control; and call the
-<constant>VIDIOC_G_EXT_CTRLS</constant> ioctl. String controls controls
-must also set the <structfield>string</structfield> field.</para>
-
- <para>If the <structfield>size</structfield> is too small to
-receive the control result (only relevant for pointer-type controls
-like strings), then the driver will set <structfield>size</structfield>
-to a valid value and return an &ENOSPC;. You should re-allocate the
-string memory to this new size and try again. It is possible that the
-same issue occurs again if the string has grown in the meantime. It is
-recommended to call &VIDIOC-QUERYCTRL; first and use
-<structfield>maximum</structfield>+1 as the new <structfield>size</structfield>
-value. It is guaranteed that that is sufficient memory.
-</para>
-
- <para>To change the value of a set of controls applications
-initialize the <structfield>id</structfield>, <structfield>size</structfield>,
-<structfield>reserved2</structfield> and
-<structfield>value/string</structfield> fields of each &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 a set of controls have correct values applications
-initialize the <structfield>id</structfield>, <structfield>size</structfield>,
-<structfield>reserved2</structfield> and
-<structfield>value/string</structfield> fields of each &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 (&eg; 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>size</structfield></entry>
- <entry></entry>
- <entry>The total size in bytes of the payload of this
-control. This is normally 0, but for pointer controls this should be
-set to the size of the memory containing the payload, or that will
-receive the payload. If <constant>VIDIOC_G_EXT_CTRLS</constant> finds
-that this value is less than is required to store
-the payload result, then it is set to a value large enough to store the
-payload result and ENOSPC is returned. Note that for string controls
-this <structfield>size</structfield> field should not be confused with the length of the string.
-This field refers to the size of the memory that contains the string.
-The actual <emphasis>length</emphasis> of the string may well be much smaller.
-</entry>
- </row>
- <row>
- <entry>__u32</entry>
- <entry><structfield>reserved2</structfield>[1]</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>char *</entry>
- <entry><structfield>string</structfield></entry>
- <entry>A pointer to a string.</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" />. Drivers that use a kernel framework for handling
-controls will also accept a value of 0 here, meaning that the controls can
-belong to any control class. Whether drivers support this can be tested by setting
-<structfield>ctrl_class</structfield> to 0 and calling <constant>VIDIOC_TRY_EXT_CTRLS</constant>
-with a <structfield>count</structfield> of 0. If that succeeds, then the driver
-supports this feature.</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. If it is equal
-to <structfield>count</structfield>, then no actual changes were made to
-controls. In other words, the error was not associated with setting a particular
-control. If it is another value, then only the controls up to <structfield>error_idx-1</structfield>
-were modified and control <structfield>error_idx</structfield> is the one that
-caused the error. The <structfield>error_idx</structfield> value is undefined
-if the ioctl returned 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 <xref
- linkend="mpeg-controls" />.</entry>
- </row>
- <row>
- <entry><constant>V4L2_CTRL_CLASS_CAMERA</constant></entry>
- <entry>0x9a0000</entry>
- <entry>The class containing camera controls.
-These controls are described in <xref
- linkend="camera-controls" />.</entry>
- </row>
- <row>
- <entry><constant>V4L2_CTRL_CLASS_FM_TX</constant></entry>
- <entry>0x9b0000</entry>
- <entry>The class containing FM Transmitter (FM TX) controls.
-These controls are described in <xref
- linkend="fm-tx-controls" />.</entry>
- </row>
- <row>
- <entry><constant>V4L2_CTRL_CLASS_FLASH</constant></entry>
- <entry>0x9c0000</entry>
- <entry>The class containing flash device controls.
-These controls are described in <xref
- linkend="flash-controls" />.</entry>
- </row>
- <row>
- <entry><constant>V4L2_CTRL_CLASS_JPEG</constant></entry>
- <entry>0x9d0000</entry>
- <entry>The class containing JPEG compression controls.
-These controls are described in <xref
- linkend="jpeg-controls" />.</entry>
- </row>
- <row>
- <entry><constant>V4L2_CTRL_CLASS_IMAGE_SOURCE</constant></entry>
- <entry>0x9e0000</entry> <entry>The class containing image
- source controls. These controls are described in <xref
- linkend="image-source-controls" />.</entry>
- </row>
- <row>
- <entry><constant>V4L2_CTRL_CLASS_IMAGE_PROC</constant></entry>
- <entry>0x9f0000</entry> <entry>The class containing image
- processing controls. These controls are described in <xref
- linkend="image-process-controls" />.</entry>
- </row>
- <row>
- <entry><constant>V4L2_CTRL_CLASS_JPEG</constant></entry>
- <entry>0x9d0000</entry>
- <entry>The class containing JPEG compression controls.
-These controls are described in <xref
- linkend="jpeg-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>
- <varlistentry>
- <term><errorcode>ENOSPC</errorcode></term>
- <listitem>
- <para>The space reserved for the control's payload is insufficient.
-The field <structfield>size</structfield> is set to a value that is enough
-to store the payload and this error code is returned.</para>
- </listitem>
- </varlistentry>
- <varlistentry>
- <term><errorcode>EACCES</errorcode></term>
- <listitem>
- <para>Attempt to try or set a read-only control or to get a
- write-only control.</para>
- </listitem>
- </varlistentry>
- </variablelist>
- </refsect1>
-</refentry>
-