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

   1 <refentry id="media-g-topology">
   2   <refmeta>
   3     <refentrytitle>ioctl MEDIA_IOC_G_TOPOLOGY</refentrytitle>
   4     &manvol;
   5   </refmeta>
   6
   7   <refnamediv>
   8     <refname>MEDIA_IOC_G_TOPOLOGY</refname>
   9     <refpurpose>Enumerate the graph topology and graph element properties</refpurpose>
  10   </refnamediv>
  11
  12   <refsynopsisdiv>
  13     <funcsynopsis>
  14       <funcprototype>
  15         <funcdef>int <function>ioctl</function></funcdef>
  16         <paramdef>int <parameter>fd</parameter></paramdef>
  17         <paramdef>int <parameter>request</parameter></paramdef>
  18         <paramdef>struct media_v2_topology *<parameter>argp</parameter></paramdef>
  19       </funcprototype>
  20     </funcsynopsis>
  21   </refsynopsisdiv>
  22
  23   <refsect1>
  24     <title>Arguments</title>
  25
  26     <variablelist>
  27       <varlistentry>
  28         <term><parameter>fd</parameter></term>
  29         <listitem>
  30           <para>File descriptor returned by
  31           <link linkend='media-func-open'><function>open()</function></link>.</para>
  32         </listitem>
  33       </varlistentry>
  34       <varlistentry>
  35         <term><parameter>request</parameter></term>
  36         <listitem>
  37           <para>MEDIA_IOC_G_TOPOLOGY</para>
  38         </listitem>
  39       </varlistentry>
  40       <varlistentry>
  41         <term><parameter>argp</parameter></term>
  42         <listitem>
  43           <para></para>
  44         </listitem>
  45       </varlistentry>
  46     </variablelist>
  47   </refsect1>
  48
  49   <refsect1>
  50     <title>Description</title>
  51     <para>The typical usage of this ioctl is to call it twice.
  52     On the first call, the structure defined at &media-v2-topology; should
  53     be zeroed. At return, if no errors happen, this ioctl will return the
  54     <constant>topology_version</constant> and the total number of entities,
  55     interfaces, pads and links.</para>
  56     <para>Before the second call, the userspace should allocate arrays to
  57     store the graph elements that are desired, putting the pointers to them
  58     at the ptr_entities, ptr_interfaces, ptr_links and/or ptr_pads, keeping
  59     the other values untouched.</para>
  60     <para>If the <constant>topology_version</constant> remains the same, the
  61     ioctl should fill the desired arrays with the media graph elements.</para>
  62
  63     <table pgwide="1" frame="none" id="media-v2-topology">
  64       <title>struct <structname>media_v2_topology</structname></title>
  65       <tgroup cols="5">
  66         <colspec colname="c1" />
  67         <colspec colname="c2" />
  68         <colspec colname="c3" />
  69         <colspec colname="c4" />
  70         <colspec colname="c5" />
  71         <tbody valign="top">
  72           <row>
  73             <entry>__u64</entry>
  74             <entry><structfield>topology_version</structfield></entry>
  75             <entry></entry>
  76             <entry></entry>
  77             <entry>Version of the media graph topology. When the graph is
  78                     created, this field starts with zero. Every time a graph
  79                     element is added or removed, this field is
  80                     incremented.</entry>
  81           </row>
  82           <row>
  83             <entry>__u64</entry>
  84             <entry><structfield>num_entities</structfield></entry>
  85             <entry></entry>
  86             <entry></entry>
  87             <entry>Number of entities in the graph</entry>
  88           </row>
  89           <row>
  90             <entry>__u64</entry>
  91             <entry><structfield>ptr_entities</structfield></entry>
  92             <entry></entry>
  93             <entry></entry>
  94             <entry>A pointer to a memory area where the entities array
  95                    will be stored, converted to a 64-bits integer.
  96                    It can be zero. if zero, the ioctl won't store the
  97                    entities. It will just update
  98                    <constant>num_entities</constant></entry>
  99           </row>
 100           <row>
 101             <entry>__u64</entry>
 102             <entry><structfield>num_interfaces</structfield></entry>
 103             <entry></entry>
 104             <entry></entry>
 105             <entry>Number of interfaces in the graph</entry>
 106           </row>
 107           <row>
 108             <entry>__u64</entry>
 109             <entry><structfield>ptr_interfaces</structfield></entry>
 110             <entry></entry>
 111             <entry></entry>
 112             <entry>A pointer to a memory area where the interfaces array
 113                    will be stored, converted to a 64-bits integer.
 114                    It can be zero. if zero, the ioctl won't store the
 115                    interfaces. It will just update
 116                    <constant>num_interfaces</constant></entry>
 117           </row>
 118           <row>
 119             <entry>__u64</entry>
 120             <entry><structfield>num_pads</structfield></entry>
 121             <entry></entry>
 122             <entry></entry>
 123             <entry>Total number of pads in the graph</entry>
 124           </row>
 125           <row>
 126             <entry>__u64</entry>
 127             <entry><structfield>ptr_pads</structfield></entry>
 128             <entry></entry>
 129             <entry></entry>
 130             <entry>A pointer to a memory area where the pads array
 131                    will be stored, converted to a 64-bits integer.
 132                    It can be zero. if zero, the ioctl won't store the
 133                    pads. It will just update
 134                    <constant>num_pads</constant></entry>
 135           </row>
 136           <row>
 137             <entry>__u64</entry>
 138             <entry><structfield>num_links</structfield></entry>
 139             <entry></entry>
 140             <entry></entry>
 141             <entry>Total number of data and interface links in the graph</entry>
 142           </row>
 143           <row>
 144             <entry>__u64</entry>
 145             <entry><structfield>ptr_links</structfield></entry>
 146             <entry></entry>
 147             <entry></entry>
 148             <entry>A pointer to a memory area where the links array
 149                    will be stored, converted to a 64-bits integer.
 150                    It can be zero. if zero, the ioctl won't store the
 151                    links. It will just update
 152                    <constant>num_links</constant></entry>
 153           </row>
 154         </tbody>
 155       </tgroup>
 156     </table>
 157
 158     <table pgwide="1" frame="none" id="media-v2-entity">
 159       <title>struct <structname>media_v2_entity</structname></title>
 160       <tgroup cols="5">
 161         <colspec colname="c1" />
 162         <colspec colname="c2" />
 163         <colspec colname="c3" />
 164         <colspec colname="c4" />
 165         <colspec colname="c5" />
 166         <tbody valign="top">
 167           <row>
 168             <entry>__u32</entry>
 169             <entry><structfield>id</structfield></entry>
 170             <entry></entry>
 171             <entry></entry>
 172             <entry>Unique ID for the entity.</entry>
 173           </row>
 174           <row>
 175             <entry>char</entry>
 176             <entry><structfield>name</structfield>[64]</entry>
 177             <entry></entry>
 178             <entry></entry>
 179             <entry>Entity name as an UTF-8 NULL-terminated string.</entry>
 180           </row>
 181           <row>
 182             <entry>__u32</entry>
 183             <entry><structfield>function</structfield></entry>
 184             <entry></entry>
 185             <entry></entry>
 186             <entry>Entity main function, see <xref linkend="media-entity-type" /> for details.</entry>
 187           </row>
 188           <row>
 189             <entry>__u32</entry>
 190             <entry><structfield>reserved</structfield>[12]</entry>
 191             <entry>Reserved for future extensions. Drivers and applications must
 192             set this array to zero.</entry>
 193           </row>
 194         </tbody>
 195       </tgroup>
 196     </table>
 197
 198     <table pgwide="1" frame="none" id="media-v2-interface">
 199       <title>struct <structname>media_v2_interface</structname></title>
 200       <tgroup cols="5">
 201         <colspec colname="c1" />
 202         <colspec colname="c2" />
 203         <colspec colname="c3" />
 204         <colspec colname="c4" />
 205         <colspec colname="c5" />
 206         <tbody valign="top">
 207           <row>
 208             <entry>__u32</entry>
 209             <entry><structfield>id</structfield></entry>
 210             <entry></entry>
 211             <entry></entry>
 212             <entry>Unique ID for the interface.</entry>
 213           </row>
 214           <row>
 215             <entry>__u32</entry>
 216             <entry><structfield>intf_type</structfield></entry>
 217             <entry></entry>
 218             <entry></entry>
 219             <entry>Interface type, see <xref linkend="media-intf-type" /> for details.</entry>
 220           </row>
 221           <row>
 222             <entry>__u32</entry>
 223             <entry><structfield>flags</structfield></entry>
 224             <entry></entry>
 225             <entry></entry>
 226             <entry>Interface flags. Currently unused.</entry>
 227           </row>
 228           <row>
 229             <entry>__u32</entry>
 230             <entry><structfield>reserved</structfield>[9]</entry>
 231             <entry></entry>
 232             <entry></entry>
 233             <entry>Reserved for future extensions. Drivers and applications must
 234             set this array to zero.</entry>
 235           </row>
 236           <row>
 237             <entry>struct media_v2_intf_devnode</entry>
 238             <entry><structfield>devnode</structfield></entry>
 239             <entry></entry>
 240             <entry></entry>
 241             <entry>Used only for device node interfaces. See <xref linkend="media-v2-intf-devnode" /> for details..</entry>
 242           </row>
 243         </tbody>
 244       </tgroup>
 245     </table>
 246
 247     <table pgwide="1" frame="none" id="media-v2-intf-devnode">
 248       <title>struct <structname>media_v2_interface</structname></title>
 249       <tgroup cols="5">
 250         <colspec colname="c1" />
 251         <colspec colname="c2" />
 252         <colspec colname="c3" />
 253         <colspec colname="c4" />
 254         <colspec colname="c5" />
 255         <tbody valign="top">
 256           <row>
 257             <entry>__u32</entry>
 258             <entry><structfield>major</structfield></entry>
 259             <entry></entry>
 260             <entry></entry>
 261             <entry>Device node major number.</entry>
 262           </row>
 263           <row>
 264             <entry>__u32</entry>
 265             <entry><structfield>minor</structfield></entry>
 266             <entry></entry>
 267             <entry></entry>
 268             <entry>Device node minor number.</entry>
 269           </row>
 270         </tbody>
 271       </tgroup>
 272     </table>
 273
 274     <table pgwide="1" frame="none" id="media-v2-pad">
 275       <title>struct <structname>media_v2_pad</structname></title>
 276       <tgroup cols="5">
 277         <colspec colname="c1" />
 278         <colspec colname="c2" />
 279         <colspec colname="c3" />
 280         <colspec colname="c4" />
 281         <colspec colname="c5" />
 282         <tbody valign="top">
 283           <row>
 284             <entry>__u32</entry>
 285             <entry><structfield>id</structfield></entry>
 286             <entry></entry>
 287             <entry></entry>
 288             <entry>Unique ID for the pad.</entry>
 289           </row>
 290           <row>
 291             <entry>__u32</entry>
 292             <entry><structfield>entity_id</structfield></entry>
 293             <entry></entry>
 294             <entry></entry>
 295             <entry>Unique ID for the entity where this pad belongs.</entry>
 296           </row>
 297           <row>
 298             <entry>__u32</entry>
 299             <entry><structfield>flags</structfield></entry>
 300             <entry></entry>
 301             <entry></entry>
 302             <entry>Pad flags, see <xref linkend="media-pad-flag" /> for more details.</entry>
 303           </row>
 304           <row>
 305             <entry>__u32</entry>
 306             <entry><structfield>reserved</structfield>[9]</entry>
 307             <entry></entry>
 308             <entry></entry>
 309             <entry>Reserved for future extensions. Drivers and applications must
 310             set this array to zero.</entry>
 311           </row>
 312         </tbody>
 313       </tgroup>
 314     </table>
 315
 316     <table pgwide="1" frame="none" id="media-v2-link">
 317       <title>struct <structname>media_v2_pad</structname></title>
 318       <tgroup cols="5">
 319         <colspec colname="c1" />
 320         <colspec colname="c2" />
 321         <colspec colname="c3" />
 322         <colspec colname="c4" />
 323         <colspec colname="c5" />
 324         <tbody valign="top">
 325           <row>
 326             <entry>__u32</entry>
 327             <entry><structfield>id</structfield></entry>
 328             <entry></entry>
 329             <entry></entry>
 330             <entry>Unique ID for the pad.</entry>
 331           </row>
 332           <row>
 333             <entry>__u32</entry>
 334             <entry><structfield>source_id</structfield></entry>
 335             <entry></entry>
 336             <entry></entry>
 337             <entry>
 338                <para>On pad to pad links: unique ID for the source pad.</para>
 339                <para>On interface to entity links: unique ID for the interface.</para>
 340             </entry>
 341           </row>
 342           <row>
 343             <entry>__u32</entry>
 344             <entry><structfield>sink_id</structfield></entry>
 345             <entry></entry>
 346             <entry></entry>
 347             <entry>
 348                <para>On pad to pad links: unique ID for the sink pad.</para>
 349                <para>On interface to entity links: unique ID for the entity.</para>
 350             </entry>
 351           </row>
 352           <row>
 353             <entry>__u32</entry>
 354             <entry><structfield>flags</structfield></entry>
 355             <entry></entry>
 356             <entry></entry>
 357             <entry>Link flags, see <xref linkend="media-link-flag" /> for more details.</entry>
 358           </row>
 359           <row>
 360             <entry>__u32</entry>
 361             <entry><structfield>reserved</structfield>[5]</entry>
 362             <entry></entry>
 363             <entry></entry>
 364             <entry>Reserved for future extensions. Drivers and applications must
 365             set this array to zero.</entry>
 366           </row>
 367         </tbody>
 368       </tgroup>
 369     </table>
 370
 371   </refsect1>
 372
 373   <refsect1>
 374     &return-value;
 375
 376     <variablelist>
 377       <varlistentry>
 378         <term><errorcode>ENOSPC</errorcode></term>
 379         <listitem>
 380           <para>This is returned when either one or more of the num_entities,
 381           num_interfaces, num_links or num_pads are non-zero and are smaller
 382           than the actual number of elements inside the graph. This may happen
 383           if the <constant>topology_version</constant> changed when compared
 384           to the last time this ioctl was called. Userspace should usually
 385           free the area for the pointers, zero the struct elements and call
 386           this ioctl again.</para>
 387         </listitem>
 388       </varlistentry>
 389     </variablelist>
 390   </refsect1>
 391 </refentry>