CooCenter-System-kernel/Documentation/DocBook/media/v4l/media-ioc-enum-entities.xml

<refentry id="media-ioc-enum-entities">
  <refmeta>
    <refentrytitle>ioctl MEDIA_IOC_ENUM_ENTITIES</refentrytitle>
    &manvol;
  </refmeta>

  <refnamediv>
    <refname>MEDIA_IOC_ENUM_ENTITIES</refname>
    <refpurpose>Enumerate entities and their properties</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 media_entity_desc *<parameter>argp</parameter></paramdef>
      </funcprototype>
    </funcsynopsis>
  </refsynopsisdiv>

  <refsect1>
    <title>Arguments</title>

    <variablelist>
      <varlistentry>
	<term><parameter>fd</parameter></term>
	<listitem>
	  <para>File descriptor returned by
	  <link linkend='media-func-open'><function>open()</function></link>.</para>
	</listitem>
      </varlistentry>
      <varlistentry>
	<term><parameter>request</parameter></term>
	<listitem>
	  <para>MEDIA_IOC_ENUM_ENTITIES</para>
	</listitem>
      </varlistentry>
      <varlistentry>
	<term><parameter>argp</parameter></term>
	<listitem>
	  <para></para>
	</listitem>
      </varlistentry>
    </variablelist>
  </refsect1>

  <refsect1>
    <title>Description</title>
    <para>To query the attributes of an entity, applications set the id field
    of a &media-entity-desc; structure and call the MEDIA_IOC_ENUM_ENTITIES
    ioctl with a pointer to this structure. The driver fills the rest of the
    structure or returns an &EINVAL; when the id is invalid.</para>
    <para>Entities can be enumerated by or'ing the id with the
    <constant>MEDIA_ENT_ID_FLAG_NEXT</constant> flag. The driver will return
    information about the entity with the smallest id strictly larger than the
    requested one ('next entity'), or the &EINVAL; if there is none.</para>
    <para>Entity IDs can be non-contiguous. Applications must
    <emphasis>not</emphasis> try to enumerate entities by calling
    MEDIA_IOC_ENUM_ENTITIES with increasing id's until they get an error.</para>
    <para>Two or more entities that share a common non-zero
    <structfield>group_id</structfield> value are considered as logically
    grouped. Groups are used to report
    <itemizedlist>
      <listitem><para>ALSA, VBI and video nodes that carry the same media
      stream</para></listitem>
      <listitem><para>lens and flash controllers associated with a sensor</para></listitem>
    </itemizedlist>
    </para>

    <table pgwide="1" frame="none" id="media-entity-desc">
      <title>struct <structname>media_entity_desc</structname></title>
      <tgroup cols="5">
	<colspec colname="c1" />
	<colspec colname="c2" />
	<colspec colname="c3" />
	<colspec colname="c4" />
	<colspec colname="c5" />
	<tbody valign="top">
	  <row>
	    <entry>__u32</entry>
	    <entry><structfield>id</structfield></entry>
	    <entry></entry>
	    <entry></entry>
	    <entry>Entity id, set by the application. When the id is or'ed with
	    <constant>MEDIA_ENT_ID_FLAG_NEXT</constant>, the driver clears the
	    flag and returns the first entity with a larger id.</entry>
	  </row>
	  <row>
	    <entry>char</entry>
	    <entry><structfield>name</structfield>[32]</entry>
	    <entry></entry>
	    <entry></entry>
	    <entry>Entity name as an UTF-8 NULL-terminated string.</entry>
	  </row>
	  <row>
	    <entry>__u32</entry>
	    <entry><structfield>type</structfield></entry>
	    <entry></entry>
	    <entry></entry>
	    <entry>Entity type, see <xref linkend="media-entity-type" /> for details.</entry>
	  </row>
	  <row>
	    <entry>__u32</entry>
	    <entry><structfield>revision</structfield></entry>
	    <entry></entry>
	    <entry></entry>
	    <entry>Entity revision in a driver/hardware specific format.</entry>
	  </row>
	  <row>
	    <entry>__u32</entry>
	    <entry><structfield>flags</structfield></entry>
	    <entry></entry>
	    <entry></entry>
	    <entry>Entity flags, see <xref linkend="media-entity-flag" /> for details.</entry>
	  </row>
	  <row>
	    <entry>__u32</entry>
	    <entry><structfield>group_id</structfield></entry>
	    <entry></entry>
	    <entry></entry>
	    <entry>Entity group ID</entry>
	  </row>
	  <row>
	    <entry>__u16</entry>
	    <entry><structfield>pads</structfield></entry>
	    <entry></entry>
	    <entry></entry>
	    <entry>Number of pads</entry>
	  </row>
	  <row>
	    <entry>__u16</entry>
	    <entry><structfield>links</structfield></entry>
	    <entry></entry>
	    <entry></entry>
	    <entry>Total number of outbound links. Inbound links are not counted
	    in this field.</entry>
	  </row>
	  <row>
	    <entry>union</entry>
	  </row>
	  <row>
	    <entry></entry>
	    <entry>struct</entry>
	    <entry><structfield>dev</structfield></entry>
	    <entry></entry>
	    <entry>Valid for (sub-)devices that create a single device node.</entry>
	  </row>
	  <row>
	    <entry></entry>
	    <entry></entry>
	    <entry>__u32</entry>
	    <entry><structfield>major</structfield></entry>
	    <entry>Device node major number.</entry>
	  </row>
	  <row>
	    <entry></entry>
	    <entry></entry>
	    <entry>__u32</entry>
	    <entry><structfield>minor</structfield></entry>
	    <entry>Device node minor number.</entry>
	  </row>
	  <row>
	    <entry></entry>
	    <entry>__u8</entry>
	    <entry><structfield>raw</structfield>[184]</entry>
	    <entry></entry>
	    <entry></entry>
	  </row>
	</tbody>
      </tgroup>
    </table>

    <table frame="none" pgwide="1" id="media-entity-type">
      <title>Media entity types</title>
      <tgroup cols="2">
        <colspec colname="c1"/>
        <colspec colname="c2"/>
	<tbody valign="top">
	  <row>
	    <entry><constant>MEDIA_ENT_T_DEVNODE</constant></entry>
	    <entry>Unknown device node</entry>
	  </row>
	  <row>
	    <entry><constant>MEDIA_ENT_T_DEVNODE_V4L</constant></entry>
	    <entry>V4L video, radio or vbi device node</entry>
	  </row>
	  <row>
	    <entry><constant>MEDIA_ENT_T_DEVNODE_FB</constant></entry>
	    <entry>Frame buffer device node</entry>
	  </row>
	  <row>
	    <entry><constant>MEDIA_ENT_T_DEVNODE_ALSA</constant></entry>
	    <entry>ALSA card</entry>
	  </row>
	  <row>
	    <entry><constant>MEDIA_ENT_T_DEVNODE_DVB_FE</constant></entry>
	    <entry>DVB frontend devnode</entry>
	  </row>
	  <row>
	    <entry><constant>MEDIA_ENT_T_DEVNODE_DVB_DEMUX</constant></entry>
	    <entry>DVB demux devnode</entry>
	  </row>
	  <row>
	    <entry><constant>MEDIA_ENT_T_DEVNODE_DVB_DVR</constant></entry>
	    <entry>DVB DVR devnode</entry>
	  </row>
	  <row>
	    <entry><constant>MEDIA_ENT_T_DEVNODE_DVB_CA</constant></entry>
	    <entry>DVB CAM devnode</entry>
	  </row>
	  <row>
	    <entry><constant>MEDIA_ENT_T_DEVNODE_DVB_NET</constant></entry>
	    <entry>DVB network devnode</entry>
	  </row>
	  <row>
	    <entry><constant>MEDIA_ENT_T_V4L2_SUBDEV</constant></entry>
	    <entry>Unknown V4L sub-device</entry>
	  </row>
	  <row>
	    <entry><constant>MEDIA_ENT_T_V4L2_SUBDEV_SENSOR</constant></entry>
	    <entry>Video sensor</entry>
	  </row>
	  <row>
	    <entry><constant>MEDIA_ENT_T_V4L2_SUBDEV_FLASH</constant></entry>
	    <entry>Flash controller</entry>
	  </row>
	  <row>
	    <entry><constant>MEDIA_ENT_T_V4L2_SUBDEV_LENS</constant></entry>
	    <entry>Lens controller</entry>
	  </row>
	  <row>
	    <entry><constant>MEDIA_ENT_T_V4L2_SUBDEV_DECODER</constant></entry>
	    <entry>Video decoder, the basic function of the video decoder is to
	    accept analogue video from a wide variety of sources such as
	    broadcast, DVD players, cameras and video cassette recorders, in
	    either NTSC, PAL or HD format and still occasionally SECAM, separate
	    it into its component parts, luminance and chrominance, and output
	    it in some digital video standard, with appropriate embedded timing
	    signals.</entry>
	  </row>
	  <row>
	    <entry><constant>MEDIA_ENT_T_V4L2_SUBDEV_TUNER</constant></entry>
	    <entry>TV and/or radio tuner</entry>
	  </row>
	</tbody>
      </tgroup>
    </table>

    <table frame="none" pgwide="1" id="media-entity-flag">
      <title>Media entity flags</title>
      <tgroup cols="2">
        <colspec colname="c1"/>
        <colspec colname="c2"/>
	<tbody valign="top">
	  <row>
	    <entry><constant>MEDIA_ENT_FL_DEFAULT</constant></entry>
	    <entry>Default entity for its type. Used to discover the default
	    audio, VBI and video devices, the default camera sensor, ...</entry>
	  </row>
	</tbody>
      </tgroup>
    </table>
  </refsect1>

  <refsect1>
    &return-value;

    <variablelist>
      <varlistentry>
	<term><errorcode>EINVAL</errorcode></term>
	<listitem>
	  <para>The &media-entity-desc; <structfield>id</structfield> references
	  a non-existing entity.</para>
	</listitem>
      </varlistentry>
    </variablelist>
  </refsect1>
</refentry>