CooCenter-System-kernel/Documentation/DocBook/media/v4l/vidioc-subdev-enum-frame-size.xml

<refentry id="vidioc-subdev-enum-frame-size">
  <refmeta>
    <refentrytitle>ioctl VIDIOC_SUBDEV_ENUM_FRAME_SIZE</refentrytitle>
    &manvol;
  </refmeta>

  <refnamediv>
    <refname>VIDIOC_SUBDEV_ENUM_FRAME_SIZE</refname>
    <refpurpose>Enumerate media bus frame sizes</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_size_enum *
	<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_ENUM_FRAME_SIZE</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>This ioctl allows applications to enumerate all frame sizes
    supported by a sub-device on the given pad for the given media bus format.
    Supported formats can be retrieved with the &VIDIOC-SUBDEV-ENUM-MBUS-CODE;
    ioctl.</para>

    <para>To enumerate frame sizes applications initialize the
    <structfield>pad</structfield>, <structfield>which</structfield> ,
    <structfield>code</structfield> and <structfield>index</structfield>
    fields of the &v4l2-subdev-mbus-code-enum; and call the
    <constant>VIDIOC_SUBDEV_ENUM_FRAME_SIZE</constant> ioctl with a pointer to
    the structure. Drivers fill the minimum and maximum frame sizes or return
    an &EINVAL; if one of the input parameters is invalid.</para>

    <para>Sub-devices that only support discrete frame sizes (such as most
    sensors) will return one or more frame sizes with identical minimum and
    maximum values.</para>

    <para>Not all possible sizes in given [minimum, maximum] ranges need to be
    supported. For instance, a scaler that uses a fixed-point scaling ratio
    might not be able to produce every frame size between the minimum and
    maximum values. Applications must use the &VIDIOC-SUBDEV-S-FMT; ioctl to
    try the sub-device for an exact supported frame size.</para>

    <para>Available frame sizes may depend on the current 'try' formats at other
    pads of the sub-device, as well as on the current active links and the
    current values of V4L2 controls. See &VIDIOC-SUBDEV-G-FMT; for more
    information about try formats.</para>

    <table pgwide="1" frame="none" id="v4l2-subdev-frame-size-enum">
      <title>struct <structname>v4l2_subdev_frame_size_enum</structname></title>
      <tgroup cols="3">
	&cs-str;
	<tbody valign="top">
	  <row>
	    <entry>__u32</entry>
	    <entry><structfield>index</structfield></entry>
	    <entry>Number of the format in the enumeration, set by the
	    application.</entry>
	  </row>
	  <row>
	    <entry>__u32</entry>
	    <entry><structfield>pad</structfield></entry>
	    <entry>Pad number as reported by the media controller API.</entry>
	  </row>
	  <row>
	    <entry>__u32</entry>
	    <entry><structfield>code</structfield></entry>
	    <entry>The media bus format code, as defined in
	    <xref linkend="v4l2-mbus-format" />.</entry>
	  </row>
	  <row>
	    <entry>__u32</entry>
	    <entry><structfield>min_width</structfield></entry>
	    <entry>Minimum frame width, in pixels.</entry>
	  </row>
	  <row>
	    <entry>__u32</entry>
	    <entry><structfield>max_width</structfield></entry>
	    <entry>Maximum frame width, in pixels.</entry>
	  </row>
	  <row>
	    <entry>__u32</entry>
	    <entry><structfield>min_height</structfield></entry>
	    <entry>Minimum frame height, in pixels.</entry>
	  </row>
	  <row>
	    <entry>__u32</entry>
	    <entry><structfield>max_height</structfield></entry>
	    <entry>Maximum frame height, in pixels.</entry>
	  </row>
	  <row>
	    <entry>__u32</entry>
	    <entry><structfield>which</structfield></entry>
	    <entry>Frame sizes to be enumerated, from &v4l2-subdev-format-whence;.</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>EINVAL</errorcode></term>
	<listitem>
	  <para>The &v4l2-subdev-frame-size-enum; <structfield>pad</structfield>
	  references a non-existing pad, the <structfield>code</structfield> is
	  invalid for the given pad or the <structfield>index</structfield>
	  field is out of bounds.</para>
	</listitem>
      </varlistentry>
    </variablelist>
  </refsect1>
</refentry>