man/hwdb.xml

   1 <?xml version='1.0'?> <!--*- Mode: nxml; nxml-child-indent: 2; indent-tabs-mode: nil -*-->
   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 <!--
   6   SPDX-License-Identifier: LGPL-2.1+
   7
   8   This file is part of systemd.
   9
  10   Copyright 2014 Tom Gundersen
  11   Copyright 2016 Zbigniew Jędrzejewski-Szmek
  12 -->
  13
  14 <refentry id="hwdb" conditional="ENABLE_HWDB">
  15   <refentryinfo>
  16     <title>hwdb</title>
  17     <productname>systemd</productname>
  18     <authorgroup>
  19       <author>
  20         <contrib>Developer</contrib>
  21         <firstname>Kay</firstname>
  22         <surname>Sievers</surname>
  23         <email>kay@vrfy.org</email>
  24       </author>
  25       <author>
  26         <contrib>Developer</contrib>
  27         <firstname>Tom</firstname>
  28         <surname>Gundersen</surname>
  29         <email>teg@jklm.no</email>
  30       </author>
  31     </authorgroup>
  32   </refentryinfo>
  33
  34   <refmeta>
  35     <refentrytitle>hwdb</refentrytitle>
  36     <manvolnum>7</manvolnum>
  37   </refmeta>
  38
  39   <refnamediv>
  40     <refname>hwdb</refname>
  41     <refpurpose>Hardware Database</refpurpose>
  42   </refnamediv>
  43
  44   <refsect1><title>Description</title>
  45     <para>The hardware database is a key-value store for associating modalias-like keys to
  46     udev-property-like values. It is used primarily by udev to add the relevant properties
  47     to matching devices, but it can also be queried directly.</para>
  48   </refsect1>
  49
  50   <refsect1><title>Hardware Database Files</title>
  51       <para>The hwdb files are read from the files located in the
  52       system hwdb directory <filename>/usr/lib/udev/hwdb.d</filename> and
  53       the local administration directory <filename>/etc/udev/hwdb.d</filename>.
  54       All hwdb files are collectively sorted and processed in lexical order,
  55       regardless of the directories in which they live. However, files with
  56       identical filenames replace each other. Files in <filename>/etc</filename>
  57       have the highest priority and take precedence over files with the same
  58       name in <filename>/usr/lib</filename>. This can be used to override a
  59       system-supplied hwdb file with a local file if needed;
  60       a symlink in <filename>/etc</filename> with the same name as a hwdb file in
  61       <filename>/usr/lib</filename>, pointing to <filename>/dev/null</filename>,
  62       disables that hwdb file entirely. hwdb files must have the extension
  63       <filename>.hwdb</filename>; other extensions are ignored.</para>
  64
  65       <para>Each hwdb file contains data records consisting of matches and associated
  66       key-value pairs. Every record in the hwdb starts with one or more match strings,
  67       specifying a shell glob to compare the lookup string against. Multiple match lines
  68       are specified in consecutive lines. Every match line is compared individually, and
  69       they are combined by OR. Every match line must start at the first character of the
  70       line.</para>
  71
  72       <para>The match lines are followed by one or more key-value pair lines, which are
  73       recognized by a leading space character. The key name and value are separated by
  74       <literal>=</literal>. An empty line signifies the end of a record. Lines beginning
  75       with <literal>#</literal> are ignored.</para>
  76
  77       <para>In case multiple records match a given lookup string, the key-value pairs
  78       from all records are combined. If a key is specified multiple times, the value
  79       from the record with the highest priority is used (each key can have only a single
  80       value). The priority is higher when the record is in a file that sorts later
  81       lexicographically, and in case of records in the same file, later records have
  82       higher priority.</para>
  83
  84       <para>The content of all hwdb files is read by
  85       <citerefentry><refentrytitle>systemd-hwdb</refentrytitle><manvolnum>8</manvolnum></citerefentry>
  86       and compiled to a binary database located at <filename>/etc/udev/hwdb.bin</filename>,
  87       or alternatively <filename>/usr/lib/udev/hwdb.bin</filename> if you want ship the
  88       compiled database in an immutable image.  During runtime, only the binary database
  89       is used.</para>
  90   </refsect1>
  91
  92   <refsect1>
  93     <title>Examples</title>
  94
  95     <example>
  96       <title>General syntax of hwdb files</title>
  97
  98       <programlisting># /usr/lib/udev/hwdb.d/example.hwdb
  99 # Comments can be placed before any records. This is a good spot
 100 # to describe what that file is used for, what kind of properties
 101 # it defines, and the ordering convention.
 102
 103 # A record with three matches and one property
 104 mouse:*:name:*Trackball*:
 105 mouse:*:name:*trackball*:
 106 mouse:*:name:*TrackBall*:
 107  ID_INPUT_TRACKBALL=1
 108
 109 # A record with a single match and five properties
 110 mouse:usb:v046dp4041:name:Logitech MX Master:
 111  MOUSE_DPI=1000@166
 112  MOUSE_WHEEL_CLICK_ANGLE=15
 113  MOUSE_WHEEL_CLICK_ANGLE_HORIZONTAL=26
 114  MOUSE_WHEEL_CLICK_COUNT=24
 115  MOUSE_WHEEL_CLICK_COUNT_HORIZONTAL=14
 116 </programlisting>
 117     </example>
 118
 119     <example>
 120       <title>Overriding of properties</title>
 121
 122       <programlisting># /usr/lib/udev/hwdb.d/60-keyboard.hwdb
 123 evdev:atkbd:dmi:bvn*:bvr*:bd*:svnAcer*:pn*
 124  KEYBOARD_KEY_a1=help
 125  KEYBOARD_KEY_a2=setup
 126  KEYBOARD_KEY_a3=battery
 127
 128 evdev:atkbd:dmi:bvn*:bvr*:bd*:svnAcer*:pn123*
 129  KEYBOARD_KEY_a2=wlan
 130
 131 # /etc/udev/hwdb.d/70-keyboard.hwdb
 132 # disable wlan key on all at keyboards
 133 evdev:atkbd:*
 134  KEYBOARD_KEY_a2=reserved</programlisting>
 135
 136       <para>If the hwdb consists of those two files, a keyboard with the lookup string
 137       <literal>evdev:atkbd:dmi:bvnAcer:bdXXXXX:bd08/05/2010:svnAcer:pn123</literal>
 138       will match all three records, and end up with the following properties:</para>
 139
 140       <programlisting>KEYBOARD_KEY_a1=help
 141 KEYBOARD_KEY_a2=reserved
 142 KEYBOARD_KEY_a3=battery</programlisting>
 143     </example>
 144   </refsect1>
 145
 146   <refsect1>
 147     <title>See Also</title>
 148     <para>
 149       <citerefentry>
 150         <refentrytitle>systemd-hwdb</refentrytitle><manvolnum>8</manvolnum>
 151       </citerefentry>
 152     </para>
 153   </refsect1>
 154 </refentry>