man/hwdb.xml

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   2 <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
   3   "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
   4 <!-- SPDX-License-Identifier: LGPL-2.1+ -->
   5
   6 <refentry id="hwdb" conditional="ENABLE_HWDB">
   7   <refentryinfo>
   8     <title>hwdb</title>
   9     <productname>systemd</productname>
  10   </refentryinfo>
  11
  12   <refmeta>
  13     <refentrytitle>hwdb</refentrytitle>
  14     <manvolnum>7</manvolnum>
  15   </refmeta>
  16
  17   <refnamediv>
  18     <refname>hwdb</refname>
  19     <refpurpose>Hardware Database</refpurpose>
  20   </refnamediv>
  21
  22   <refsect1><title>Description</title>
  23     <para>The hardware database is a key-value store for associating modalias-like keys to
  24     udev-property-like values. It is used primarily by udev to add the relevant properties
  25     to matching devices, but it can also be queried directly.</para>
  26   </refsect1>
  27
  28   <refsect1><title>Hardware Database Files</title>
  29       <para>The hwdb files are read from the files located in the
  30       system hwdb directory <filename>/usr/lib/udev/hwdb.d</filename> and
  31       the local administration directory <filename>/etc/udev/hwdb.d</filename>.
  32       All hwdb files are collectively sorted and processed in lexical order,
  33       regardless of the directories in which they live. However, files with
  34       identical filenames replace each other. Files in <filename>/etc/</filename>
  35       have the highest priority and take precedence over files with the same
  36       name in <filename>/usr/lib/</filename>. This can be used to override a
  37       system-supplied hwdb file with a local file if needed;
  38       a symlink in <filename>/etc/</filename> with the same name as a hwdb file in
  39       <filename>/usr/lib/</filename>, pointing to <filename>/dev/null</filename>,
  40       disables that hwdb file entirely. hwdb files must have the extension
  41       <filename>.hwdb</filename>; other extensions are ignored.</para>
  42
  43       <para>Each hwdb file contains data records consisting of matches and associated
  44       key-value pairs. Every record in the hwdb starts with one or more match strings,
  45       specifying a shell glob to compare the lookup string against. Multiple match lines
  46       are specified in consecutive lines. Every match line is compared individually, and
  47       they are combined by OR. Every match line must start at the first character of the
  48       line.</para>
  49
  50       <para>Match patterns consist of literal characters, and shell-style wildcards:</para>
  51       <itemizedlist>
  52         <listitem><para>Asterisk <literal>*</literal> matches any number of characters
  53         </para></listitem>
  54         <listitem><para>Question mark <literal>?</literal> matches a single character
  55         </para></listitem>
  56         <listitem><para>Character list <literal>[<replaceable>chars</replaceable>]</literal> matches one of
  57         the characters <replaceable>chars</replaceable> listed between <literal>[</literal> and
  58         <literal>]</literal>. A range may be specified as with a dash as
  59         <literal>[<replaceable>first</replaceable>-<replaceable>last</replaceable>]</literal>. The match may
  60         be inverted with a caret <literal>[^…]</literal>.</para></listitem>
  61       </itemizedlist>
  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 # The rule above could be also be written in a form that
 101 # matches Tb, tb, TB, tB:
 102 mouse:*:name:*[tT]rack[bB]all*:*
 103  ID_INPUT_TRACKBALL=1
 104
 105 # A record with a single match and five properties
 106 mouse:usb:v046dp4041:name:Logitech MX Master:*
 107  MOUSE_DPI=1000@166
 108  MOUSE_WHEEL_CLICK_ANGLE=15
 109  MOUSE_WHEEL_CLICK_ANGLE_HORIZONTAL=26
 110  MOUSE_WHEEL_CLICK_COUNT=24
 111  MOUSE_WHEEL_CLICK_COUNT_HORIZONTAL=14
 112 </programlisting>
 113     </example>
 114
 115     <example>
 116       <title>Overriding of properties</title>
 117
 118       <programlisting># /usr/lib/udev/hwdb.d/60-keyboard.hwdb
 119 evdev:atkbd:dmi:bvn*:bvr*:bd*:svnAcer*:pn*:*
 120  KEYBOARD_KEY_a1=help
 121  KEYBOARD_KEY_a2=setup
 122  KEYBOARD_KEY_a3=battery
 123
 124 # Match vendor name "Acer" and any product name starting with "X123"
 125 evdev:atkbd:dmi:bvn*:bvr*:bd*:svnAcer:pnX123*:*
 126  KEYBOARD_KEY_a2=wlan
 127
 128 # /etc/udev/hwdb.d/70-keyboard.hwdb
 129 # disable wlan key on all at keyboards
 130 evdev:atkbd:*
 131  KEYBOARD_KEY_a2=reserved
 132  PROPERTY_WITH_SPACES=some string</programlisting>
 133
 134       <para>If the hwdb consists of those two files, a keyboard with the lookup string
 135       <literal>evdev:atkbd:dmi:bvnAcer:bdXXXXX:bd08/05/2010:svnAcer:pnX123</literal>
 136       will match all three records, and end up with the following properties:</para>
 137
 138       <programlisting>KEYBOARD_KEY_a1=help
 139 KEYBOARD_KEY_a2=reserved
 140 KEYBOARD_KEY_a3=battery
 141 PROPERTY_WITH_SPACES=some string</programlisting>
 142
 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>