Documentation/DocBook/media/v4l/media-ioc-device-info.xml

   1 <refentry id="media-ioc-device-info">
   2   <refmeta>
   3     <refentrytitle>ioctl MEDIA_IOC_DEVICE_INFO</refentrytitle>
   4     &manvol;
   5   </refmeta>
   6
   7   <refnamediv>
   8     <refname>MEDIA_IOC_DEVICE_INFO</refname>
   9     <refpurpose>Query device information</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_device_info *<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_DEVICE_INFO</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
  52     <para>All media devices must support the <constant>MEDIA_IOC_DEVICE_INFO</constant>
  53     ioctl. To query device information, applications call the ioctl with a
  54     pointer to a &media-device-info;. The driver fills the structure and returns
  55     the information to the application.
  56     The ioctl never fails.</para>
  57
  58     <table pgwide="1" frame="none" id="media-device-info">
  59       <title>struct <structname>media_device_info</structname></title>
  60       <tgroup cols="3">
  61         &cs-str;
  62         <tbody valign="top">
  63           <row>
  64             <entry>char</entry>
  65             <entry><structfield>driver</structfield>[16]</entry>
  66             <entry><para>Name of the driver implementing the media API as a
  67             NUL-terminated ASCII string. The driver version is stored in the
  68             <structfield>driver_version</structfield> field.</para>
  69             <para>Driver specific applications can use this information to
  70             verify the driver identity. It is also useful to work around
  71             known bugs, or to identify drivers in error reports.</para></entry>
  72           </row>
  73           <row>
  74             <entry>char</entry>
  75             <entry><structfield>model</structfield>[32]</entry>
  76             <entry>Device model name as a NUL-terminated UTF-8 string. The
  77             device version is stored in the <structfield>device_version</structfield>
  78             field and is not be appended to the model name.</entry>
  79           </row>
  80           <row>
  81             <entry>char</entry>
  82             <entry><structfield>serial</structfield>[40]</entry>
  83             <entry>Serial number as a NUL-terminated ASCII string.</entry>
  84           </row>
  85           <row>
  86             <entry>char</entry>
  87             <entry><structfield>bus_info</structfield>[32]</entry>
  88             <entry>Location of the device in the system as a NUL-terminated
  89             ASCII string. This includes the bus type name (PCI, USB, ...) and a
  90             bus-specific identifier.</entry>
  91           </row>
  92           <row>
  93             <entry>__u32</entry>
  94             <entry><structfield>media_version</structfield></entry>
  95             <entry>Media API version, formatted with the
  96             <constant>KERNEL_VERSION()</constant> macro.</entry>
  97           </row>
  98           <row>
  99             <entry>__u32</entry>
 100             <entry><structfield>hw_revision</structfield></entry>
 101             <entry>Hardware device revision in a driver-specific format.</entry>
 102           </row>
 103           <row>
 104             <entry>__u32</entry>
 105             <entry><structfield>driver_version</structfield></entry>
 106             <entry>Media device driver version, formatted with the
 107             <constant>KERNEL_VERSION()</constant> macro. Together with the
 108             <structfield>driver</structfield> field this identifies a particular
 109             driver.</entry>
 110           </row>
 111           <row>
 112             <entry>__u32</entry>
 113             <entry><structfield>reserved</structfield>[31]</entry>
 114             <entry>Reserved for future extensions. Drivers and applications must
 115             set this array to zero.</entry>
 116           </row>
 117         </tbody>
 118       </tgroup>
 119     </table>
 120     <para>The <structfield>serial</structfield> and <structfield>bus_info</structfield>
 121     fields can be used to distinguish between multiple instances of otherwise
 122     identical hardware. The serial number takes precedence when provided and can
 123     be assumed to be unique. If the serial number is an empty string, the
 124     <structfield>bus_info</structfield> field can be used instead. The
 125     <structfield>bus_info</structfield> field is guaranteed to be unique, but
 126     can vary across reboots or device unplug/replug.</para>
 127   </refsect1>
 128
 129   <refsect1>
 130     &return-value;
 131   </refsect1>
 132 </refentry>