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c643ee1351
Add control class for image processing controls. The control class deals with controls processing image, for example digital gain or noise filtering, which can be present in any part of the pipeline. Signed-off-by: Sakari Ailus <sakari.ailus@iki.fi> Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
342 lines
12 KiB
XML
342 lines
12 KiB
XML
<refentry id="vidioc-g-ext-ctrls">
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<refmeta>
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<refentrytitle>ioctl VIDIOC_G_EXT_CTRLS, VIDIOC_S_EXT_CTRLS,
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VIDIOC_TRY_EXT_CTRLS</refentrytitle>
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&manvol;
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</refmeta>
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<refnamediv>
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<refname>VIDIOC_G_EXT_CTRLS</refname>
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<refname>VIDIOC_S_EXT_CTRLS</refname>
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<refname>VIDIOC_TRY_EXT_CTRLS</refname>
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<refpurpose>Get or set the value of several controls, try control
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values</refpurpose>
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</refnamediv>
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<refsynopsisdiv>
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<funcsynopsis>
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<funcprototype>
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<funcdef>int <function>ioctl</function></funcdef>
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<paramdef>int <parameter>fd</parameter></paramdef>
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<paramdef>int <parameter>request</parameter></paramdef>
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<paramdef>struct v4l2_ext_controls
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*<parameter>argp</parameter></paramdef>
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</funcprototype>
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</funcsynopsis>
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</refsynopsisdiv>
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<refsect1>
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<title>Arguments</title>
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<variablelist>
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<varlistentry>
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<term><parameter>fd</parameter></term>
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<listitem>
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<para>&fd;</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><parameter>request</parameter></term>
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<listitem>
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<para>VIDIOC_G_EXT_CTRLS, VIDIOC_S_EXT_CTRLS,
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VIDIOC_TRY_EXT_CTRLS</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><parameter>argp</parameter></term>
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<listitem>
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<para></para>
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</listitem>
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</varlistentry>
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</variablelist>
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</refsect1>
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<refsect1>
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<title>Description</title>
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<para>These ioctls allow the caller to get or set multiple
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controls atomically. Control IDs are grouped into control classes (see
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<xref linkend="ctrl-class" />) and all controls in the control array
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must belong to the same control class.</para>
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<para>Applications must always fill in the
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<structfield>count</structfield>,
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<structfield>ctrl_class</structfield>,
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<structfield>controls</structfield> and
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<structfield>reserved</structfield> fields of &v4l2-ext-controls;, and
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initialize the &v4l2-ext-control; array pointed to by the
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<structfield>controls</structfield> fields.</para>
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<para>To get the current value of a set of controls applications
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initialize the <structfield>id</structfield>,
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<structfield>size</structfield> and <structfield>reserved2</structfield> fields
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of each &v4l2-ext-control; and call the
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<constant>VIDIOC_G_EXT_CTRLS</constant> ioctl. String controls controls
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must also set the <structfield>string</structfield> field.</para>
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<para>If the <structfield>size</structfield> is too small to
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receive the control result (only relevant for pointer-type controls
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like strings), then the driver will set <structfield>size</structfield>
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to a valid value and return an &ENOSPC;. You should re-allocate the
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string memory to this new size and try again. It is possible that the
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same issue occurs again if the string has grown in the meantime. It is
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recommended to call &VIDIOC-QUERYCTRL; first and use
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<structfield>maximum</structfield>+1 as the new <structfield>size</structfield>
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value. It is guaranteed that that is sufficient memory.
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</para>
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<para>To change the value of a set of controls applications
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initialize the <structfield>id</structfield>, <structfield>size</structfield>,
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<structfield>reserved2</structfield> and
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<structfield>value/string</structfield> fields of each &v4l2-ext-control; and
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call the <constant>VIDIOC_S_EXT_CTRLS</constant> ioctl. The controls
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will only be set if <emphasis>all</emphasis> control values are
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valid.</para>
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<para>To check if a set of controls have correct values applications
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initialize the <structfield>id</structfield>, <structfield>size</structfield>,
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<structfield>reserved2</structfield> and
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<structfield>value/string</structfield> fields of each &v4l2-ext-control; and
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call the <constant>VIDIOC_TRY_EXT_CTRLS</constant> ioctl. It is up to
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the driver whether wrong values are automatically adjusted to a valid
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value or if an error is returned.</para>
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<para>When the <structfield>id</structfield> or
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<structfield>ctrl_class</structfield> is invalid drivers return an
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&EINVAL;. When the value is out of bounds drivers can choose to take
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the closest valid value or return an &ERANGE;, whatever seems more
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appropriate. In the first case the new value is set in
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&v4l2-ext-control;.</para>
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<para>The driver will only set/get these controls if all control
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values are correct. This prevents the situation where only some of the
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controls were set/get. Only low-level errors (⪚ a failed i2c
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command) can still cause this situation.</para>
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<table pgwide="1" frame="none" id="v4l2-ext-control">
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<title>struct <structname>v4l2_ext_control</structname></title>
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<tgroup cols="4">
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&cs-ustr;
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<tbody valign="top">
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<row>
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<entry>__u32</entry>
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<entry><structfield>id</structfield></entry>
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<entry></entry>
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<entry>Identifies the control, set by the
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application.</entry>
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</row>
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<row>
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<entry>__u32</entry>
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<entry><structfield>size</structfield></entry>
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<entry></entry>
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<entry>The total size in bytes of the payload of this
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control. This is normally 0, but for pointer controls this should be
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set to the size of the memory containing the payload, or that will
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receive the payload. If <constant>VIDIOC_G_EXT_CTRLS</constant> finds
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that this value is less than is required to store
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the payload result, then it is set to a value large enough to store the
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payload result and ENOSPC is returned. Note that for string controls
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this <structfield>size</structfield> field should not be confused with the length of the string.
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This field refers to the size of the memory that contains the string.
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The actual <emphasis>length</emphasis> of the string may well be much smaller.
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</entry>
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</row>
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<row>
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<entry>__u32</entry>
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<entry><structfield>reserved2</structfield>[1]</entry>
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<entry></entry>
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<entry>Reserved for future extensions. Drivers and
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applications must set the array to zero.</entry>
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</row>
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<row>
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<entry>union</entry>
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<entry>(anonymous)</entry>
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</row>
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<row>
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<entry></entry>
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<entry>__s32</entry>
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<entry><structfield>value</structfield></entry>
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<entry>New value or current value.</entry>
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</row>
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<row>
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<entry></entry>
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<entry>__s64</entry>
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<entry><structfield>value64</structfield></entry>
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<entry>New value or current value.</entry>
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</row>
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<row>
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<entry></entry>
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<entry>char *</entry>
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<entry><structfield>string</structfield></entry>
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<entry>A pointer to a string.</entry>
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</row>
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</tbody>
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</tgroup>
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</table>
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<table pgwide="1" frame="none" id="v4l2-ext-controls">
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<title>struct <structname>v4l2_ext_controls</structname></title>
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<tgroup cols="3">
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&cs-str;
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<tbody valign="top">
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<row>
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<entry>__u32</entry>
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<entry><structfield>ctrl_class</structfield></entry>
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<entry>The control class to which all controls belong, see
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<xref linkend="ctrl-class" />. Drivers that use a kernel framework for handling
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controls will also accept a value of 0 here, meaning that the controls can
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belong to any control class. Whether drivers support this can be tested by setting
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<structfield>ctrl_class</structfield> to 0 and calling <constant>VIDIOC_TRY_EXT_CTRLS</constant>
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with a <structfield>count</structfield> of 0. If that succeeds, then the driver
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supports this feature.</entry>
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</row>
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<row>
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<entry>__u32</entry>
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<entry><structfield>count</structfield></entry>
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<entry>The number of controls in the controls array. May
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also be zero.</entry>
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</row>
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<row>
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<entry>__u32</entry>
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<entry><structfield>error_idx</structfield></entry>
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<entry>Set by the driver in case of an error. If it is equal
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to <structfield>count</structfield>, then no actual changes were made to
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controls. In other words, the error was not associated with setting a particular
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control. If it is another value, then only the controls up to <structfield>error_idx-1</structfield>
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were modified and control <structfield>error_idx</structfield> is the one that
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caused the error. The <structfield>error_idx</structfield> value is undefined
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if the ioctl returned 0 (success).</entry>
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</row>
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<row>
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<entry>__u32</entry>
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<entry><structfield>reserved</structfield>[2]</entry>
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<entry>Reserved for future extensions. Drivers and
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applications must set the array to zero.</entry>
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</row>
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<row>
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<entry>&v4l2-ext-control; *</entry>
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<entry><structfield>controls</structfield></entry>
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<entry>Pointer to an array of
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<structfield>count</structfield> v4l2_ext_control structures. Ignored
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if <structfield>count</structfield> equals zero.</entry>
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</row>
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</tbody>
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</tgroup>
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</table>
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<table pgwide="1" frame="none" id="ctrl-class">
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<title>Control classes</title>
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<tgroup cols="3">
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&cs-def;
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<tbody valign="top">
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<row>
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<entry><constant>V4L2_CTRL_CLASS_USER</constant></entry>
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<entry>0x980000</entry>
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<entry>The class containing user controls. These controls
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are described in <xref linkend="control" />. All controls that can be set
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using the &VIDIOC-S-CTRL; and &VIDIOC-G-CTRL; ioctl belong to this
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class.</entry>
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</row>
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<row>
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<entry><constant>V4L2_CTRL_CLASS_MPEG</constant></entry>
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<entry>0x990000</entry>
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<entry>The class containing MPEG compression controls.
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These controls are described in <xref
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linkend="mpeg-controls" />.</entry>
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</row>
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<row>
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<entry><constant>V4L2_CTRL_CLASS_CAMERA</constant></entry>
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<entry>0x9a0000</entry>
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<entry>The class containing camera controls.
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These controls are described in <xref
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linkend="camera-controls" />.</entry>
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</row>
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<row>
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<entry><constant>V4L2_CTRL_CLASS_FM_TX</constant></entry>
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<entry>0x9b0000</entry>
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<entry>The class containing FM Transmitter (FM TX) controls.
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These controls are described in <xref
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linkend="fm-tx-controls" />.</entry>
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</row>
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<row>
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<entry><constant>V4L2_CTRL_CLASS_FLASH</constant></entry>
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<entry>0x9c0000</entry>
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<entry>The class containing flash device controls.
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These controls are described in <xref
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linkend="flash-controls" />.</entry>
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</row>
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<row>
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<entry><constant>V4L2_CTRL_CLASS_JPEG</constant></entry>
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<entry>0x9d0000</entry>
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<entry>The class containing JPEG compression controls.
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These controls are described in <xref
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linkend="jpeg-controls" />.</entry>
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</row>
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<row>
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<entry><constant>V4L2_CTRL_CLASS_IMAGE_SOURCE</constant></entry>
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<entry>0x9e0000</entry> <entry>The class containing image
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source controls. These controls are described in <xref
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linkend="image-source-controls" />.</entry>
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</row>
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<row>
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<entry><constant>V4L2_CTRL_CLASS_IMAGE_PROC</constant></entry>
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<entry>0x9f0000</entry> <entry>The class containing image
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processing controls. These controls are described in <xref
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linkend="image-process-controls" />.</entry>
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</row>
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</tbody>
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</tgroup>
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</table>
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</refsect1>
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<refsect1>
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&return-value;
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<variablelist>
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<varlistentry>
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<term><errorcode>EINVAL</errorcode></term>
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<listitem>
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<para>The &v4l2-ext-control; <structfield>id</structfield>
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is invalid or the &v4l2-ext-controls;
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<structfield>ctrl_class</structfield> is invalid. This error code is
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also returned by the <constant>VIDIOC_S_EXT_CTRLS</constant> and
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<constant>VIDIOC_TRY_EXT_CTRLS</constant> ioctls if two or more
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control values are in conflict.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><errorcode>ERANGE</errorcode></term>
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<listitem>
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<para>The &v4l2-ext-control; <structfield>value</structfield>
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is out of bounds.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><errorcode>EBUSY</errorcode></term>
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<listitem>
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<para>The control is temporarily not changeable, possibly
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because another applications took over control of the device function
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this control belongs to.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><errorcode>ENOSPC</errorcode></term>
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<listitem>
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<para>The space reserved for the control's payload is insufficient.
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The field <structfield>size</structfield> is set to a value that is enough
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to store the payload and this error code is returned.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><errorcode>EACCES</errorcode></term>
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<listitem>
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<para>Attempt to try or set a read-only control or to get a
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write-only control.</para>
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</listitem>
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</varlistentry>
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</variablelist>
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</refsect1>
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</refentry>
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