142 lines
5.0 KiB
XML
142 lines
5.0 KiB
XML
<refentry id="vidioc-subdev-g-frame-interval">
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<refmeta>
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<refentrytitle>ioctl VIDIOC_SUBDEV_G_FRAME_INTERVAL, VIDIOC_SUBDEV_S_FRAME_INTERVAL</refentrytitle>
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&manvol;
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</refmeta>
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<refnamediv>
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<refname>VIDIOC_SUBDEV_G_FRAME_INTERVAL</refname>
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<refname>VIDIOC_SUBDEV_S_FRAME_INTERVAL</refname>
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<refpurpose>Get or set the frame interval on a subdev pad</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_subdev_frame_interval *<parameter>argp</parameter>
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</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_SUBDEV_G_FRAME_INTERVAL, VIDIOC_SUBDEV_S_FRAME_INTERVAL</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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<note>
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<title>Experimental</title>
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<para>This is an <link linkend="experimental">experimental</link>
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interface and may change in the future.</para>
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</note>
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<para>These ioctls are used to get and set the frame interval at specific
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subdev pads in the image pipeline. The frame interval only makes sense for
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sub-devices that can control the frame period on their own. This includes,
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for instance, image sensors and TV tuners. Sub-devices that don't support
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frame intervals must not implement these ioctls.</para>
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<para>To retrieve the current frame interval applications set the
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<structfield>pad</structfield> field of a &v4l2-subdev-frame-interval; to
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the desired pad number as reported by the media controller API. When they
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call the <constant>VIDIOC_SUBDEV_G_FRAME_INTERVAL</constant> ioctl with a
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pointer to this structure the driver fills the members of the
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<structfield>interval</structfield> field.</para>
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<para>To change the current frame interval applications set both the
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<structfield>pad</structfield> field and all members of the
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<structfield>interval</structfield> field. When they call the
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<constant>VIDIOC_SUBDEV_S_FRAME_INTERVAL</constant> ioctl with a pointer to
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this structure the driver verifies the requested interval, adjusts it based
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on the hardware capabilities and configures the device. Upon return the
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&v4l2-subdev-frame-interval; contains the current frame interval as would be
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returned by a <constant>VIDIOC_SUBDEV_G_FRAME_INTERVAL</constant> call.
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</para>
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<para>Drivers must not return an error solely because the requested interval
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doesn't match the device capabilities. They must instead modify the interval
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to match what the hardware can provide. The modified interval should be as
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close as possible to the original request.</para>
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<para>Sub-devices that support the frame interval ioctls should implement
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them on a single pad only. Their behaviour when supported on multiple pads
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of the same sub-device is not defined.</para>
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<table pgwide="1" frame="none" id="v4l2-subdev-frame-interval">
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<title>struct <structname>v4l2_subdev_frame_interval</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>pad</structfield></entry>
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<entry>Pad number as reported by the media controller API.</entry>
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</row>
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<row>
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<entry>&v4l2-fract;</entry>
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<entry><structfield>interval</structfield></entry>
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<entry>Period, in seconds, between consecutive video frames.</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>[9]</entry>
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<entry>Reserved for future extensions. Applications and drivers must
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set 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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</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>EBUSY</errorcode></term>
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<listitem>
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<para>The frame interval can't be changed because the pad is currently
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busy. This can be caused, for instance, by an active video stream on
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the pad. The ioctl must not be retried without performing another
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action to fix the problem first. Only returned by
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<constant>VIDIOC_SUBDEV_S_FRAME_INTERVAL</constant></para>
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</listitem>
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</varlistentry>
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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-subdev-frame-interval; <structfield>pad</structfield>
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references a non-existing pad, or the pad doesn't support frame
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intervals.</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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