linux/Documentation/DocBook/media/v4l/vidioc-subdev-g-selection.xml

<refentry id="vidioc-subdev-g-selection">
  <refmeta>
    <refentrytitle>ioctl VIDIOC_SUBDEV_G_SELECTION, VIDIOC_SUBDEV_S_SELECTION</refentrytitle>
    &manvol;
  </refmeta>

  <refnamediv>
    <refname>VIDIOC_SUBDEV_G_SELECTION</refname>
    <refname>VIDIOC_SUBDEV_S_SELECTION</refname>
    <refpurpose>Get or set selection rectangles 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_selection *<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_SELECTION, VIDIOC_SUBDEV_S_SELECTION</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>The selections are used to configure various image
    processing functionality performed by the subdevs which affect the
    image size. This currently includes cropping, scaling and
    composition.</para>

    <para>The selection API replaces <link
    linkend="vidioc-subdev-g-crop">the old subdev crop API</link>. All
    the function of the crop API, and more, are supported by the
    selections API.</para>

    <para>See <xref linkend="subdev"></xref> for
    more information on how each selection target affects the image
    processing pipeline inside the subdevice.</para>

    <section>
      <title>Types of selection targets</title>

      <para>There are two types of selection targets: actual and bounds. The
      actual targets are the targets which configure the hardware. The BOUNDS
      target will return a rectangle that contain all possible actual
      rectangles.</para>
    </section>

    <section>
      <title>Discovering supported features</title>

      <para>To discover which targets are supported, the user can
      perform <constant>VIDIOC_SUBDEV_G_SELECTION</constant> on them.
      Any unsupported target will return
      <constant>EINVAL</constant>.</para>
    </section>

    <para>Selection targets are documented in <xref
    linkend="v4l2-selections-common"/>.</para>

    <table pgwide="1" frame="none" id="v4l2-subdev-selection-flags">
      <title>V4L2 subdev selection flags</title>
      <tgroup cols="3">
        &cs-def;
	<tbody valign="top">
	  <row>
	    <entry><constant>V4L2_SUBDEV_SEL_FLAG_SIZE_GE</constant></entry>
	    <entry>(1 &lt;&lt; 0)</entry> <entry>Suggest the driver it
	    should choose greater or equal rectangle (in size) than
	    was requested. Albeit the driver may choose a lesser size,
	    it will only do so due to hardware limitations. Without
	    this flag (and
	    <constant>V4L2_SUBDEV_SEL_FLAG_SIZE_LE</constant>) the
	    behaviour is to choose the closest possible
	    rectangle.</entry>
	  </row>
	  <row>
	    <entry><constant>V4L2_SUBDEV_SEL_FLAG_SIZE_LE</constant></entry>
	    <entry>(1 &lt;&lt; 1)</entry> <entry>Suggest the driver it
	    should choose lesser or equal rectangle (in size) than was
	    requested. Albeit the driver may choose a greater size, it
	    will only do so due to hardware limitations.</entry>
	  </row>
	  <row>
	    <entry><constant>V4L2_SUBDEV_SEL_FLAG_KEEP_CONFIG</constant></entry>
	    <entry>(1 &lt;&lt; 2)</entry>
	    <entry>The configuration should not be propagated to any
	    further processing steps. If this flag is not given, the
	    configuration is propagated inside the subdevice to all
	    further processing steps.</entry>
	  </row>
	</tbody>
      </tgroup>
    </table>

    <table pgwide="1" frame="none" id="v4l2-subdev-selection">
      <title>struct <structname>v4l2_subdev_selection</structname></title>
      <tgroup cols="3">
        &cs-str;
	<tbody valign="top">
	  <row>
	    <entry>__u32</entry>
	    <entry><structfield>which</structfield></entry>
	    <entry>Active or try selection, from
	    &v4l2-subdev-format-whence;.</entry>
	  </row>
	  <row>
	    <entry>__u32</entry>
	    <entry><structfield>pad</structfield></entry>
	    <entry>Pad number as reported by the media framework.</entry>
	  </row>
	  <row>
	    <entry>__u32</entry>
	    <entry><structfield>target</structfield></entry>
	    <entry>Target selection rectangle. See
	    <xref linkend="v4l2-selections-common" />.</entry>
	  </row>
	  <row>
	    <entry>__u32</entry>
	    <entry><structfield>flags</structfield></entry>
	    <entry>Flags. See
	    <xref linkend="v4l2-subdev-selection-flags">.</xref></entry>
	  </row>
	  <row>
	    <entry>&v4l2-rect;</entry>
	    <entry><structfield>rect</structfield></entry>
	    <entry>Selection rectangle, in pixels.</entry>
	  </row>
	  <row>
	    <entry>__u32</entry>
	    <entry><structfield>reserved</structfield>[8]</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 selection rectangle 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_SELECTION</constant></para>
	</listitem>
      </varlistentry>
      <varlistentry>
	<term><errorcode>EINVAL</errorcode></term>
	<listitem>
	  <para>The &v4l2-subdev-selection;
	  <structfield>pad</structfield> references a non-existing
	  pad, the <structfield>which</structfield> field references a
	  non-existing format, or the selection target is not
	  supported on the given subdev pad.</para>
	</listitem>
      </varlistentry>
    </variablelist>
  </refsect1>
</refentry>