CooCenter-System-kernel/Documentation/DocBook/media/v4l/vidioc-enum-dv-timings.xml

<refentry id="vidioc-enum-dv-timings">
  <refmeta>
    <refentrytitle>ioctl VIDIOC_ENUM_DV_TIMINGS, VIDIOC_SUBDEV_ENUM_DV_TIMINGS</refentrytitle>
    &manvol;
  </refmeta>

  <refnamediv>
    <refname>VIDIOC_ENUM_DV_TIMINGS</refname>
    <refname>VIDIOC_SUBDEV_ENUM_DV_TIMINGS</refname>
    <refpurpose>Enumerate supported Digital Video timings</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_enum_dv_timings *<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_ENUM_DV_TIMINGS, VIDIOC_SUBDEV_ENUM_DV_TIMINGS</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>While some DV receivers or transmitters support a wide range of timings, others
support only a limited number of timings. With this ioctl applications can enumerate a list
of known supported timings. Call &VIDIOC-DV-TIMINGS-CAP; to check if it also supports other
standards or even custom timings that are not in this list.</para>

    <para>To query the available timings, applications initialize the
<structfield>index</structfield> field and zero the reserved array of &v4l2-enum-dv-timings;
and call the <constant>VIDIOC_ENUM_DV_TIMINGS</constant> ioctl on a video node with a
pointer to this structure. Drivers fill the rest of the structure or return an
&EINVAL; when the index is out of bounds. To enumerate all supported DV timings,
applications shall begin at index zero, incrementing by one until the
driver returns <errorcode>EINVAL</errorcode>. Note that drivers may enumerate a
different set of DV timings after switching the video input or
output.</para>

    <para>When implemented by the driver DV timings of subdevices can be queried
by calling the <constant>VIDIOC_SUBDEV_ENUM_DV_TIMINGS</constant> ioctl directly
on a subdevice node. The DV timings are specific to inputs (for DV receivers) or
outputs (for DV transmitters), applications must specify the desired pad number
in the &v4l2-enum-dv-timings; <structfield>pad</structfield> field. Attempts to
enumerate timings on a pad that doesn't support them will return an &EINVAL;.</para>

    <table pgwide="1" frame="none" id="v4l2-enum-dv-timings">
      <title>struct <structname>v4l2_enum_dv_timings</structname></title>
      <tgroup cols="3">
	&cs-str;
	<tbody valign="top">
	  <row>
	    <entry>__u32</entry>
	    <entry><structfield>index</structfield></entry>
	    <entry>Number of the DV timings, 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. This field
	    is only used when operating on a subdevice node. When operating on a
	    video node applications must set this field to zero.</entry>
	  </row>
	  <row>
	    <entry>__u32</entry>
	    <entry><structfield>reserved</structfield>[2]</entry>
	    <entry>Reserved for future extensions. Drivers and applications must
	    set the array to zero.</entry>
	  </row>
	  <row>
	    <entry>&v4l2-dv-timings;</entry>
	    <entry><structfield>timings</structfield></entry>
	    <entry>The timings.</entry>
	  </row>
	</tbody>
      </tgroup>
    </table>
  </refsect1>

  <refsect1>
    &return-value;

    <variablelist>
      <varlistentry>
	<term><errorcode>EINVAL</errorcode></term>
	<listitem>
	  <para>The &v4l2-enum-dv-timings; <structfield>index</structfield>
is out of bounds or the <structfield>pad</structfield> number is invalid.</para>
	</listitem>
      </varlistentry>
      <varlistentry>
	<term><errorcode>ENODATA</errorcode></term>
	<listitem>
	  <para>Digital video presets are not supported for this input or output.</para>
	</listitem>
      </varlistentry>
    </variablelist>
  </refsect1>
</refentry>