man/hwdb.xml

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   2 <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
   3   "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
   4
   5 <refentry id="hwdb" conditional="ENABLE_HWDB">
   6   <refentryinfo>
   7     <title>hwdb</title>
   8     <productname>systemd</productname>
   9     <authorgroup>
  10       <author>
  11         <contrib>Developer</contrib>
  12         <firstname>Kay</firstname>
  13         <surname>Sievers</surname>
  14         <email>kay@vrfy.org</email>
  15       </author>
  16       <author>
  17         <contrib>Developer</contrib>
  18         <firstname>Tom</firstname>
  19         <surname>Gundersen</surname>
  20         <email>teg@jklm.no</email>
  21       </author>
  22     </authorgroup>
  23   </refentryinfo>
  24
  25   <refmeta>
  26     <refentrytitle>hwdb</refentrytitle>
  27     <manvolnum>7</manvolnum>
  28   </refmeta>
  29
  30   <refnamediv>
  31     <refname>hwdb</refname>
  32     <refpurpose>Hardware Database</refpurpose>
  33   </refnamediv>
  34
  35   <refsect1><title>Description</title>
  36     <para>The hardware database is a key-value store for associating modalias-like keys to
  37     udev-property-like values. It is used primarily by udev to add the relevant properties
  38     to matching devices, but it can also be queried directly.</para>
  39   </refsect1>
  40
  41   <refsect1><title>Hardware Database Files</title>
  42       <para>The hwdb files are read from the files located in the
  43       system hwdb directory <filename>/usr/lib/udev/hwdb.d</filename> and
  44       the local administration directory <filename>/etc/udev/hwdb.d</filename>.
  45       All hwdb files are collectively sorted and processed in lexical order,
  46       regardless of the directories in which they live. However, files with
  47       identical filenames replace each other. Files in <filename>/etc</filename>
  48       have the highest priority and take precedence over files with the same
  49       name in <filename>/usr/lib</filename>. This can be used to override a
  50       system-supplied hwdb file with a local file if needed;
  51       a symlink in <filename>/etc</filename> with the same name as a hwdb file in
  52       <filename>/usr/lib</filename>, pointing to <filename>/dev/null</filename>,
  53       disables that hwdb file entirely. hwdb files must have the extension
  54       <filename>.hwdb</filename>; other extensions are ignored.</para>
  55
  56       <para>Each hwdb file contains data records consisting of matches and associated
  57       key-value pairs. Every record in the hwdb starts with one or more match strings,
  58       specifying a shell glob to compare the lookup string against. Multiple match lines
  59       are specified in consecutive lines. Every match line is compared individually, and
  60       they are combined by OR. Every match line must start at the first character of the
  61       line.</para>
  62
  63       <para>The match lines are followed by one or more key-value pair lines, which are
  64       recognized by a leading space character. The key name and value are separated by
  65       <literal>=</literal>. An empty line signifies the end of a record. Lines beginning
  66       with <literal>#</literal> are ignored.</para>
  67
  68       <para>In case multiple records match a given lookup string, the key-value pairs
  69       from all records are combined. If a key is specified multiple times, the value
  70       from the record with the highest priority is used (each key can have only a single
  71       value). The priority is higher when the record is in a file that sorts later
  72       lexicographically, and in case of records in the same file, later records have
  73       higher priority.</para>
  74
  75       <para>The content of all hwdb files is read by
  76       <citerefentry><refentrytitle>systemd-hwdb</refentrytitle><manvolnum>8</manvolnum></citerefentry>
  77       and compiled to a binary database located at <filename>/etc/udev/hwdb.bin</filename>,
  78       or alternatively <filename>/usr/lib/udev/hwdb.bin</filename> if you want ship the
  79       compiled database in an immutable image.  During runtime, only the binary database
  80       is used.</para>
  81   </refsect1>
  82
  83   <refsect1>
  84     <title>Examples</title>
  85
  86     <example>
  87       <title>General syntax of hwdb files</title>
  88
  89       <programlisting># /usr/lib/udev/hwdb.d/example.hwdb
  90 # Comments can be placed before any records. This is a good spot
  91 # to describe what that file is used for, what kind of properties
  92 # it defines, and the ordering convention.
  93
  94 # A record with three matches and one property
  95 mouse:*:name:*Trackball*:
  96 mouse:*:name:*trackball*:
  97 mouse:*:name:*TrackBall*:
  98  ID_INPUT_TRACKBALL=1
  99
 100 # A record with a single match and five properties
 101 mouse:usb:v046dp4041:name:Logitech MX Master:
 102  MOUSE_DPI=1000@166
 103  MOUSE_WHEEL_CLICK_ANGLE=15
 104  MOUSE_WHEEL_CLICK_ANGLE_HORIZONTAL=26
 105  MOUSE_WHEEL_CLICK_COUNT=24
 106  MOUSE_WHEEL_CLICK_COUNT_HORIZONTAL=14
 107 </programlisting>
 108     </example>
 109
 110     <example>
 111       <title>Overriding of properties</title>
 112
 113       <programlisting># /usr/lib/udev/hwdb.d/60-keyboard.hwdb
 114 evdev:atkbd:dmi:bvn*:bvr*:bd*:svnAcer*:pn*
 115  KEYBOARD_KEY_a1=help
 116  KEYBOARD_KEY_a2=setup
 117  KEYBOARD_KEY_a3=battery
 118
 119 evdev:atkbd:dmi:bvn*:bvr*:bd*:svnAcer*:pn123*
 120  KEYBOARD_KEY_a2=wlan
 121
 122 # /etc/udev/hwdb.d/70-keyboard.hwdb
 123 # disable wlan key on all at keyboards
 124 evdev:atkbd:*
 125  KEYBOARD_KEY_a2=reserved</programlisting>
 126
 127       <para>If the hwdb consists of those two files, a keyboard with the lookup string
 128       <literal>evdev:atkbd:dmi:bvnAcer:bdXXXXX:bd08/05/2010:svnAcer:pn123</literal>
 129       will match all three records, and end up with the following properties:</para>
 130
 131       <programlisting>KEYBOARD_KEY_a1=help
 132 KEYBOARD_KEY_a2=reserved
 133 KEYBOARD_KEY_a3=battery</programlisting>
 134     </example>
 135   </refsect1>
 136
 137   <refsect1>
 138     <title>See Also</title>
 139     <para>
 140       <citerefentry>
 141         <refentrytitle>systemd-hwdb</refentrytitle><manvolnum>8</manvolnum>
 142       </citerefentry>
 143     </para>
 144   </refsect1>
 145 </refentry>