Documentation/DocBook/media/v4l/media-ioc-g-topology.xml

<refentry id="media-g-topology">
  <refmeta>
    <refentrytitle>ioctl MEDIA_IOC_G_TOPOLOGY</refentrytitle>
    &manvol;
  </refmeta>

  <refnamediv>
    <refname>MEDIA_IOC_G_TOPOLOGY</refname>
    <refpurpose>Enumerate the graph topology and graph element 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_v2_topology *<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_G_TOPOLOGY</para>
	</listitem>
      </varlistentry>
      <varlistentry>
	<term><parameter>argp</parameter></term>
	<listitem>
	  <para></para>
	</listitem>
      </varlistentry>
    </variablelist>
  </refsect1>

  <refsect1>
    <title>Description</title>

    <para><emphasis role="bold">NOTE:</emphasis> This new ioctl is programmed to be added on Kernel 4.6. Its definition/arguments may change until its final version.</para>

    <para>The typical usage of this ioctl is to call it twice.
    On the first call, the structure defined at &media-v2-topology; should
    be zeroed. At return, if no errors happen, this ioctl will return the
    <constant>topology_version</constant> and the total number of entities,
    interfaces, pads and links.</para>
    <para>Before the second call, the userspace should allocate arrays to
    store the graph elements that are desired, putting the pointers to them
    at the ptr_entities, ptr_interfaces, ptr_links and/or ptr_pads, keeping
    the other values untouched.</para>
    <para>If the <constant>topology_version</constant> remains the same, the
    ioctl should fill the desired arrays with the media graph elements.</para>

    <table pgwide="1" frame="none" id="media-v2-topology">
      <title>struct <structname>media_v2_topology</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>__u64</entry>
	    <entry><structfield>topology_version</structfield></entry>
	    <entry></entry>
	    <entry></entry>
	    <entry>Version of the media graph topology. When the graph is
		    created, this field starts with zero. Every time a graph
		    element is added or removed, this field is
		    incremented.</entry>
	  </row>
	  <row>
	    <entry>__u64</entry>
	    <entry><structfield>num_entities</structfield></entry>
	    <entry></entry>
	    <entry></entry>
	    <entry>Number of entities in the graph</entry>
	  </row>
	  <row>
	    <entry>__u64</entry>
	    <entry><structfield>ptr_entities</structfield></entry>
	    <entry></entry>
	    <entry></entry>
	    <entry>A pointer to a memory area where the entities array
		   will be stored, converted to a 64-bits integer.
		   It can be zero. if zero, the ioctl won't store the
		   entities. It will just update
		   <constant>num_entities</constant></entry>
	  </row>
	  <row>
	    <entry>__u64</entry>
	    <entry><structfield>num_interfaces</structfield></entry>
	    <entry></entry>
	    <entry></entry>
	    <entry>Number of interfaces in the graph</entry>
	  </row>
	  <row>
	    <entry>__u64</entry>
	    <entry><structfield>ptr_interfaces</structfield></entry>
	    <entry></entry>
	    <entry></entry>
	    <entry>A pointer to a memory area where the interfaces array
		   will be stored, converted to a 64-bits integer.
		   It can be zero. if zero, the ioctl won't store the
		   interfaces. It will just update
		   <constant>num_interfaces</constant></entry>
	  </row>
	  <row>
	    <entry>__u64</entry>
	    <entry><structfield>num_pads</structfield></entry>
	    <entry></entry>
	    <entry></entry>
	    <entry>Total number of pads in the graph</entry>
	  </row>
	  <row>
	    <entry>__u64</entry>
	    <entry><structfield>ptr_pads</structfield></entry>
	    <entry></entry>
	    <entry></entry>
	    <entry>A pointer to a memory area where the pads array
		   will be stored, converted to a 64-bits integer.
		   It can be zero. if zero, the ioctl won't store the
		   pads. It will just update
		   <constant>num_pads</constant></entry>
	  </row>
	  <row>
	    <entry>__u64</entry>
	    <entry><structfield>num_links</structfield></entry>
	    <entry></entry>
	    <entry></entry>
	    <entry>Total number of data and interface links in the graph</entry>
	  </row>
	  <row>
	    <entry>__u64</entry>
	    <entry><structfield>ptr_links</structfield></entry>
	    <entry></entry>
	    <entry></entry>
	    <entry>A pointer to a memory area where the links array
		   will be stored, converted to a 64-bits integer.
		   It can be zero. if zero, the ioctl won't store the
		   links. It will just update
		   <constant>num_links</constant></entry>
	  </row>
	</tbody>
      </tgroup>
    </table>

    <table pgwide="1" frame="none" id="media-v2-entity">
      <title>struct <structname>media_v2_entity</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>Unique ID for the entity.</entry>
	  </row>
	  <row>
	    <entry>char</entry>
	    <entry><structfield>name</structfield>[64]</entry>
	    <entry></entry>
	    <entry></entry>
	    <entry>Entity name as an UTF-8 NULL-terminated string.</entry>
	  </row>
	  <row>
	    <entry>__u32</entry>
	    <entry><structfield>function</structfield></entry>
	    <entry></entry>
	    <entry></entry>
	    <entry>Entity main function, see <xref linkend="media-entity-type" /> for details.</entry>
	  </row>
	  <row>
	    <entry>__u32</entry>
	    <entry><structfield>reserved</structfield>[12]</entry>
	    <entry>Reserved for future extensions. Drivers and applications must
	    set this array to zero.</entry>
	  </row>
	</tbody>
      </tgroup>
    </table>

    <table pgwide="1" frame="none" id="media-v2-interface">
      <title>struct <structname>media_v2_interface</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>Unique ID for the interface.</entry>
	  </row>
	  <row>
	    <entry>__u32</entry>
	    <entry><structfield>intf_type</structfield></entry>
	    <entry></entry>
	    <entry></entry>
	    <entry>Interface type, see <xref linkend="media-intf-type" /> for details.</entry>
	  </row>
	  <row>
	    <entry>__u32</entry>
	    <entry><structfield>flags</structfield></entry>
	    <entry></entry>
	    <entry></entry>
	    <entry>Interface flags. Currently unused.</entry>
	  </row>
	  <row>
	    <entry>__u32</entry>
	    <entry><structfield>reserved</structfield>[9]</entry>
	    <entry></entry>
	    <entry></entry>
	    <entry>Reserved for future extensions. Drivers and applications must
	    set this array to zero.</entry>
	  </row>
	  <row>
	    <entry>struct media_v2_intf_devnode</entry>
	    <entry><structfield>devnode</structfield></entry>
	    <entry></entry>
	    <entry></entry>
	    <entry>Used only for device node interfaces. See <xref linkend="media-v2-intf-devnode" /> for details..</entry>
	  </row>
	</tbody>
      </tgroup>
    </table>

    <table pgwide="1" frame="none" id="media-v2-intf-devnode">
      <title>struct <structname>media_v2_interface</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>major</structfield></entry>
	    <entry></entry>
	    <entry></entry>
	    <entry>Device node major number.</entry>
	  </row>
	  <row>
	    <entry>__u32</entry>
	    <entry><structfield>minor</structfield></entry>
	    <entry></entry>
	    <entry></entry>
	    <entry>Device node minor number.</entry>
	  </row>
	</tbody>
      </tgroup>
    </table>

    <table pgwide="1" frame="none" id="media-v2-pad">
      <title>struct <structname>media_v2_pad</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>Unique ID for the pad.</entry>
	  </row>
	  <row>
	    <entry>__u32</entry>
	    <entry><structfield>entity_id</structfield></entry>
	    <entry></entry>
	    <entry></entry>
	    <entry>Unique ID for the entity where this pad belongs.</entry>
	  </row>
	  <row>
	    <entry>__u32</entry>
	    <entry><structfield>flags</structfield></entry>
	    <entry></entry>
	    <entry></entry>
	    <entry>Pad flags, see <xref linkend="media-pad-flag" /> for more details.</entry>
	  </row>
	  <row>
	    <entry>__u32</entry>
	    <entry><structfield>reserved</structfield>[9]</entry>
	    <entry></entry>
	    <entry></entry>
	    <entry>Reserved for future extensions. Drivers and applications must
	    set this array to zero.</entry>
	  </row>
	</tbody>
      </tgroup>
    </table>

    <table pgwide="1" frame="none" id="media-v2-link">
      <title>struct <structname>media_v2_pad</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>Unique ID for the pad.</entry>
	  </row>
	  <row>
	    <entry>__u32</entry>
	    <entry><structfield>source_id</structfield></entry>
	    <entry></entry>
	    <entry></entry>
	    <entry>
	       <para>On pad to pad links: unique ID for the source pad.</para>
	       <para>On interface to entity links: unique ID for the interface.</para>
	    </entry>
	  </row>
	  <row>
	    <entry>__u32</entry>
	    <entry><structfield>sink_id</structfield></entry>
	    <entry></entry>
	    <entry></entry>
	    <entry>
	       <para>On pad to pad links: unique ID for the sink pad.</para>
	       <para>On interface to entity links: unique ID for the entity.</para>
	    </entry>
	  </row>
	  <row>
	    <entry>__u32</entry>
	    <entry><structfield>flags</structfield></entry>
	    <entry></entry>
	    <entry></entry>
	    <entry>Link flags, see <xref linkend="media-link-flag" /> for more details.</entry>
	  </row>
	  <row>
	    <entry>__u32</entry>
	    <entry><structfield>reserved</structfield>[5]</entry>
	    <entry></entry>
	    <entry></entry>
	    <entry>Reserved for future extensions. Drivers and applications must
	    set this array to zero.</entry>
	  </row>
	</tbody>
      </tgroup>
    </table>

  </refsect1>

  <refsect1>
    &return-value;

    <variablelist>
      <varlistentry>
	<term><errorcode>ENOSPC</errorcode></term>
	<listitem>
	  <para>This is returned when either one or more of the num_entities,
	  num_interfaces, num_links or num_pads are non-zero and are smaller
	  than the actual number of elements inside the graph. This may happen
	  if the <constant>topology_version</constant> changed when compared
	  to the last time this ioctl was called. Userspace should usually
	  free the area for the pointers, zero the struct elements and call
	  this ioctl again.</para>
	</listitem>
      </varlistentry>
    </variablelist>
  </refsect1>
</refentry>