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+<?xml version='1.0'?>
+<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
+ "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
+<!-- SPDX-License-Identifier: LGPL-2.1-or-later -->
+
+<refentry id="hwdb" conditional="ENABLE_HWDB">
+ <refentryinfo>
+ <title>hwdb</title>
+ <productname>systemd</productname>
+ </refentryinfo>
+
+ <refmeta>
+ <refentrytitle>hwdb</refentrytitle>
+ <manvolnum>7</manvolnum>
+ </refmeta>
+
+ <refnamediv>
+ <refname>hwdb</refname>
+ <refpurpose>Hardware Database</refpurpose>
+ </refnamediv>
+
+ <refsect1><title>Description</title>
+ <para>The hardware database is a key-value store for associating modalias-like keys to
+ udev-property-like values. It is used primarily by udev to add the relevant properties
+ to matching devices, but it can also be queried directly.</para>
+ </refsect1>
+
+ <refsect1><title>Hardware Database Files</title>
+ <para>The hwdb files are read from the files located in the
+ system hwdb directory <filename>/usr/lib/udev/hwdb.d</filename> and
+ the local administration directory <filename>/etc/udev/hwdb.d</filename>.
+ All hwdb files are collectively sorted and processed in lexical order,
+ regardless of the directories in which they live. However, files with
+ identical filenames replace each other. Files in <filename>/etc/</filename>
+ have the highest priority and take precedence over files with the same
+ name in <filename>/usr/lib/</filename>. This can be used to override a
+ system-supplied hwdb file with a local file if needed;
+ a symlink in <filename>/etc/</filename> with the same name as a hwdb file in
+ <filename>/usr/lib/</filename>, pointing to <filename>/dev/null</filename>,
+ disables that hwdb file entirely. hwdb files must have the extension
+ <filename>.hwdb</filename>; other extensions are ignored.</para>
+
+ <para>Each hwdb file contains data records consisting of matches and associated
+ key-value pairs. Every record in the hwdb starts with one or more match strings,
+ specifying a shell glob to compare the lookup string against. Multiple match lines
+ are specified in consecutive lines. Every match line is compared individually, and
+ they are combined by OR. Every match line must start at the first character of the
+ line.</para>
+
+ <para>Match patterns consist of literal characters, and shell-style wildcards:</para>
+ <itemizedlist>
+ <listitem><para>Asterisk <literal>*</literal> matches any number of characters
+ </para></listitem>
+ <listitem><para>Question mark <literal>?</literal> matches a single character
+ </para></listitem>
+ <listitem><para>Character list <literal>[<replaceable>chars</replaceable>]</literal> matches one of
+ the characters <replaceable>chars</replaceable> listed between <literal>[</literal> and
+ <literal>]</literal>. A range may be specified as with a dash as
+ <literal>[<replaceable>first</replaceable>-<replaceable>last</replaceable>]</literal>. The match may
+ be inverted with a caret <literal>[^…]</literal>.</para></listitem>
+ </itemizedlist>
+
+ <para>The match lines are followed by one or more key-value pair lines, which are
+ recognized by a leading space character. The key name and value are separated by
+ <literal>=</literal>. An empty line signifies the end of a record. Lines beginning
+ with <literal>#</literal> are ignored.</para>
+
+ <para>In case multiple records match a given lookup string, the key-value pairs
+ from all records are combined. If a key is specified multiple times, the value
+ from the record with the highest priority is used (each key can have only a single
+ value). The priority is higher when the record is in a file that sorts later
+ lexicographically, and in case of records in the same file, later records have
+ higher priority.</para>
+
+ <para>The content of all hwdb files is read by
+ <citerefentry><refentrytitle>systemd-hwdb</refentrytitle><manvolnum>8</manvolnum></citerefentry>
+ and compiled to a binary database located at <filename>/etc/udev/hwdb.bin</filename>,
+ or alternatively <filename>/usr/lib/udev/hwdb.bin</filename> if you want ship the
+ compiled database in an immutable image. During runtime, only the binary database
+ is used.</para>
+ </refsect1>
+
+ <refsect1>
+ <title>Examples</title>
+
+ <example>
+ <title>General syntax of hwdb files</title>
+
+ <programlisting># /usr/lib/udev/hwdb.d/example.hwdb
+# Comments can be placed before any records. This is a good spot
+# to describe what that file is used for, what kind of properties
+# it defines, and the ordering convention.
+
+# A record with three matches and one property
+mouse:*:name:*Trackball*:*
+mouse:*:name:*trackball*:*
+mouse:*:name:*TrackBall*:*
+ ID_INPUT_TRACKBALL=1
+
+# The rule above could be also be written in a form that
+# matches Tb, tb, TB, tB:
+mouse:*:name:*[tT]rack[bB]all*:*
+ ID_INPUT_TRACKBALL=1
+
+# A record with a single match and five properties
+mouse:usb:v046dp4041:name:Logitech MX Master:*
+ MOUSE_DPI=1000@166
+ MOUSE_WHEEL_CLICK_ANGLE=15
+ MOUSE_WHEEL_CLICK_ANGLE_HORIZONTAL=26
+ MOUSE_WHEEL_CLICK_COUNT=24
+ MOUSE_WHEEL_CLICK_COUNT_HORIZONTAL=14
+</programlisting>
+ </example>
+
+ <example>
+ <title>Overriding of properties</title>
+
+ <programlisting># /usr/lib/udev/hwdb.d/60-keyboard.hwdb
+evdev:atkbd:dmi:bvn*:bvr*:bd*:svnAcer*:pn*:*
+ KEYBOARD_KEY_a1=help
+ KEYBOARD_KEY_a2=setup
+ KEYBOARD_KEY_a3=battery
+
+# Match vendor name "Acer" and any product name starting with "X123"
+evdev:atkbd:dmi:bvn*:bvr*:bd*:svnAcer:pnX123*:*
+ KEYBOARD_KEY_a2=wlan
+
+# /etc/udev/hwdb.d/70-keyboard.hwdb
+# disable wlan key on all at keyboards
+evdev:atkbd:*
+ KEYBOARD_KEY_a2=reserved
+ PROPERTY_WITH_SPACES=some string</programlisting>
+
+ <para>If the hwdb consists of those two files, a keyboard with the lookup string
+ <literal>evdev:atkbd:dmi:bvnAcer:bdXXXXX:bd08/05/2010:svnAcer:pnX123</literal>
+ will match all three records, and end up with the following properties:</para>
+
+ <programlisting>KEYBOARD_KEY_a1=help
+KEYBOARD_KEY_a2=reserved
+KEYBOARD_KEY_a3=battery
+PROPERTY_WITH_SPACES=some string</programlisting>
+
+ </example>
+ </refsect1>
+
+ <refsect1>
+ <title>See Also</title>
+ <para>
+ <citerefentry>
+ <refentrytitle>systemd-hwdb</refentrytitle><manvolnum>8</manvolnum>
+ </citerefentry>
+ </para>
+ </refsect1>
+</refentry>