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Diffstat (limited to 'Documentation/DocBook/media/v4l/vidioc-subdev-g-frame-interval.xml')
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diff --git a/Documentation/DocBook/media/v4l/vidioc-subdev-g-frame-interval.xml b/Documentation/DocBook/media/v4l/vidioc-subdev-g-frame-interval.xml new file mode 100644 index 00000000000..0bc3ea22d31 --- /dev/null +++ b/Documentation/DocBook/media/v4l/vidioc-subdev-g-frame-interval.xml @@ -0,0 +1,141 @@ +<refentry id="vidioc-subdev-g-frame-interval"> + <refmeta> + <refentrytitle>ioctl VIDIOC_SUBDEV_G_FRAME_INTERVAL, VIDIOC_SUBDEV_S_FRAME_INTERVAL</refentrytitle> + &manvol; + </refmeta> + + <refnamediv> + <refname>VIDIOC_SUBDEV_G_FRAME_INTERVAL</refname> + <refname>VIDIOC_SUBDEV_S_FRAME_INTERVAL</refname> + <refpurpose>Get or set the frame interval on a subdev pad</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_subdev_frame_interval *<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_SUBDEV_G_FRAME_INTERVAL, VIDIOC_SUBDEV_S_FRAME_INTERVAL</para> + </listitem> + </varlistentry> + <varlistentry> + <term><parameter>argp</parameter></term> + <listitem> + <para></para> + </listitem> + </varlistentry> + </variablelist> + </refsect1> + + <refsect1> + <title>Description</title> + + <note> + <title>Experimental</title> + <para>This is an <link linkend="experimental">experimental</link> + interface and may change in the future.</para> + </note> + + <para>These ioctls are used to get and set the frame interval at specific + subdev pads in the image pipeline. The frame interval only makes sense for + sub-devices that can control the frame period on their own. This includes, + for instance, image sensors and TV tuners. Sub-devices that don't support + frame intervals must not implement these ioctls.</para> + + <para>To retrieve the current frame interval applications set the + <structfield>pad</structfield> field of a &v4l2-subdev-frame-interval; to + the desired pad number as reported by the media controller API. When they + call the <constant>VIDIOC_SUBDEV_G_FRAME_INTERVAL</constant> ioctl with a + pointer to this structure the driver fills the members of the + <structfield>interval</structfield> field.</para> + + <para>To change the current frame interval applications set both the + <structfield>pad</structfield> field and all members of the + <structfield>interval</structfield> field. When they call the + <constant>VIDIOC_SUBDEV_S_FRAME_INTERVAL</constant> ioctl with a pointer to + this structure the driver verifies the requested interval, adjusts it based + on the hardware capabilities and configures the device. Upon return the + &v4l2-subdev-frame-interval; contains the current frame interval as would be + returned by a <constant>VIDIOC_SUBDEV_G_FRAME_INTERVAL</constant> call. + </para> + + <para>Drivers must not return an error solely because the requested interval + doesn't match the device capabilities. They must instead modify the interval + to match what the hardware can provide. The modified interval should be as + close as possible to the original request.</para> + + <para>Sub-devices that support the frame interval ioctls should implement + them on a single pad only. Their behaviour when supported on multiple pads + of the same sub-device is not defined.</para> + + <table pgwide="1" frame="none" id="v4l2-subdev-frame-interval"> + <title>struct <structname>v4l2_subdev_frame_interval</structname></title> + <tgroup cols="3"> + &cs-str; + <tbody valign="top"> + <row> + <entry>__u32</entry> + <entry><structfield>pad</structfield></entry> + <entry>Pad number as reported by the media controller API.</entry> + </row> + <row> + <entry>&v4l2-fract;</entry> + <entry><structfield>interval</structfield></entry> + <entry>Period, in seconds, between consecutive video frames.</entry> + </row> + <row> + <entry>__u32</entry> + <entry><structfield>reserved</structfield>[9]</entry> + <entry>Reserved for future extensions. Applications and drivers must + set the array to zero.</entry> + </row> + </tbody> + </tgroup> + </table> + </refsect1> + + <refsect1> + &return-value; + + <variablelist> + <varlistentry> + <term><errorcode>EBUSY</errorcode></term> + <listitem> + <para>The frame interval can't be changed because the pad is currently + busy. This can be caused, for instance, by an active video stream on + the pad. The ioctl must not be retried without performing another + action to fix the problem first. Only returned by + <constant>VIDIOC_SUBDEV_S_FRAME_INTERVAL</constant></para> + </listitem> + </varlistentry> + <varlistentry> + <term><errorcode>EINVAL</errorcode></term> + <listitem> + <para>The &v4l2-subdev-frame-interval; <structfield>pad</structfield> + references a non-existing pad, or the pad doesn't support frame + intervals.</para> + </listitem> + </varlistentry> + </variablelist> + </refsect1> +</refentry> |