mirror of https://gitee.com/openkylin/linux.git
272 lines
7.7 KiB
XML
272 lines
7.7 KiB
XML
<refentry id="vidioc-dqevent">
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<refmeta>
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<refentrytitle>ioctl VIDIOC_DQEVENT</refentrytitle>
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&manvol;
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</refmeta>
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<refnamediv>
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<refname>VIDIOC_DQEVENT</refname>
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<refpurpose>Dequeue event</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_event
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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_DQEVENT</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>Dequeue an event from a video device. No input is required
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for this ioctl. All the fields of the &v4l2-event; structure are
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filled by the driver. The file handle will also receive exceptions
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which the application may get by e.g. using the select system
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call.</para>
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<table frame="none" pgwide="1" id="v4l2-event">
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<title>struct <structname>v4l2_event</structname></title>
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<tgroup cols="4">
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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>type</structfield></entry>
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<entry></entry>
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<entry>Type of the event.</entry>
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</row>
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<row>
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<entry>union</entry>
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<entry><structfield>u</structfield></entry>
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<entry></entry>
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<entry></entry>
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</row>
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<row>
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<entry></entry>
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<entry>&v4l2-event-vsync;</entry>
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<entry><structfield>vsync</structfield></entry>
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<entry>Event data for event V4L2_EVENT_VSYNC.
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</entry>
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</row>
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<row>
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<entry></entry>
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<entry>&v4l2-event-ctrl;</entry>
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<entry><structfield>ctrl</structfield></entry>
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<entry>Event data for event V4L2_EVENT_CTRL.
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</entry>
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</row>
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<row>
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<entry></entry>
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<entry>&v4l2-event-frame-sync;</entry>
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<entry><structfield>frame</structfield></entry>
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<entry>Event data for event V4L2_EVENT_FRAME_SYNC.</entry>
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</row>
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<row>
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<entry></entry>
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<entry>__u8</entry>
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<entry><structfield>data</structfield>[64]</entry>
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<entry>Event data. Defined by the event type. The union
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should be used to define easily accessible type for
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events.</entry>
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</row>
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<row>
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<entry>__u32</entry>
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<entry><structfield>pending</structfield></entry>
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<entry></entry>
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<entry>Number of pending events excluding this one.</entry>
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</row>
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<row>
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<entry>__u32</entry>
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<entry><structfield>sequence</structfield></entry>
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<entry></entry>
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<entry>Event sequence number. The sequence number is
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incremented for every subscribed event that takes place.
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If sequence numbers are not contiguous it means that
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events have been lost.
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</entry>
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</row>
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<row>
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<entry>struct timespec</entry>
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<entry><structfield>timestamp</structfield></entry>
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<entry></entry>
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<entry>Event timestamp.</entry>
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</row>
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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>The ID associated with the event source. If the event does not
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have an associated ID (this depends on the event type), then this
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is 0.</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>[8]</entry>
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<entry></entry>
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<entry>Reserved for future extensions. Drivers must set
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the array to 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 frame="none" pgwide="1" id="v4l2-event-vsync">
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<title>struct <structname>v4l2_event_vsync</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>__u8</entry>
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<entry><structfield>field</structfield></entry>
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<entry>The upcoming field. See &v4l2-field;.</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 frame="none" pgwide="1" id="v4l2-event-ctrl">
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<title>struct <structname>v4l2_event_ctrl</structname></title>
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<tgroup cols="4">
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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>changes</structfield></entry>
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<entry></entry>
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<entry>A bitmask that tells what has changed. See <xref linkend="changes-flags" />.</entry>
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</row>
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<row>
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<entry>__u32</entry>
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<entry><structfield>type</structfield></entry>
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<entry></entry>
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<entry>The type of the control. See &v4l2-ctrl-type;.</entry>
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</row>
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<row>
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<entry>union (anonymous)</entry>
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<entry></entry>
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<entry></entry>
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<entry></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>The 32-bit value of the control for 32-bit control types.
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This is 0 for string controls since the value of a string
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cannot be passed using &VIDIOC-DQEVENT;.</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>The 64-bit value of the control for 64-bit control types.</entry>
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</row>
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<row>
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<entry>__u32</entry>
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<entry><structfield>flags</structfield></entry>
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<entry></entry>
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<entry>The control flags. See <xref linkend="control-flags" />.</entry>
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</row>
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<row>
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<entry>__s32</entry>
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<entry><structfield>minimum</structfield></entry>
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<entry></entry>
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<entry>The minimum value of the control. See &v4l2-queryctrl;.</entry>
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</row>
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<row>
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<entry>__s32</entry>
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<entry><structfield>maximum</structfield></entry>
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<entry></entry>
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<entry>The maximum value of the control. See &v4l2-queryctrl;.</entry>
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</row>
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<row>
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<entry>__s32</entry>
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<entry><structfield>step</structfield></entry>
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<entry></entry>
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<entry>The step value of the control. See &v4l2-queryctrl;.</entry>
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</row>
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<row>
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<entry>__s32</entry>
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<entry><structfield>default_value</structfield></entry>
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<entry></entry>
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<entry>The default value value of the control. See &v4l2-queryctrl;.</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 frame="none" pgwide="1" id="v4l2-event-frame-sync">
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<title>struct <structname>v4l2_event_frame_sync</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>frame_sequence</structfield></entry>
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<entry>
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The sequence number of the frame being received.
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</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="changes-flags">
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<title>Changes</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_EVENT_CTRL_CH_VALUE</constant></entry>
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<entry>0x0001</entry>
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<entry>This control event was triggered because the value of the control
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changed. Special case: if a button control is pressed, then this
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event is sent as well, even though there is not explicit value
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associated with a button control.</entry>
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</row>
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<row>
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<entry><constant>V4L2_EVENT_CTRL_CH_FLAGS</constant></entry>
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<entry>0x0002</entry>
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<entry>This control event was triggered because the control flags
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changed.</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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</refsect1>
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</refentry>
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