mirror of
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![Zbigniew Jędrzejewski-Szmek](/assets/img/avatar_default.png)
Files which are installed as-is (any .service and other unit files, .conf files, .policy files, etc), are left as is. My assumption is that SPDX identifiers are not yet that well known, so it's better to retain the extended header to avoid any doubt. I also kept any copyright lines. We can probably remove them, but it'd nice to obtain explicit acks from all involved authors before doing that.
155 lines
5.8 KiB
XML
155 lines
5.8 KiB
XML
<?xml version='1.0'?> <!--*- Mode: nxml; nxml-child-indent: 2; indent-tabs-mode: nil -*-->
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<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
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"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
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<!--
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SPDX-License-Identifier: LGPL-2.1+
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This file is part of systemd.
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Copyright 2014 Tom Gundersen
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Copyright 2016 Zbigniew Jędrzejewski-Szmek
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-->
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<refentry id="hwdb" conditional="ENABLE_HWDB">
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<refentryinfo>
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<title>hwdb</title>
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<productname>systemd</productname>
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<authorgroup>
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<author>
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<contrib>Developer</contrib>
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<firstname>Kay</firstname>
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<surname>Sievers</surname>
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<email>kay@vrfy.org</email>
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</author>
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<author>
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<contrib>Developer</contrib>
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<firstname>Tom</firstname>
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<surname>Gundersen</surname>
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<email>teg@jklm.no</email>
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</author>
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</authorgroup>
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</refentryinfo>
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<refmeta>
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<refentrytitle>hwdb</refentrytitle>
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<manvolnum>7</manvolnum>
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</refmeta>
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<refnamediv>
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<refname>hwdb</refname>
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<refpurpose>Hardware Database</refpurpose>
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</refnamediv>
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<refsect1><title>Description</title>
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<para>The hardware database is a key-value store for associating modalias-like keys to
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udev-property-like values. It is used primarily by udev to add the relevant properties
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to matching devices, but it can also be queried directly.</para>
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</refsect1>
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<refsect1><title>Hardware Database Files</title>
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<para>The hwdb files are read from the files located in the
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system hwdb directory <filename>/usr/lib/udev/hwdb.d</filename> and
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the local administration directory <filename>/etc/udev/hwdb.d</filename>.
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All hwdb files are collectively sorted and processed in lexical order,
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regardless of the directories in which they live. However, files with
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identical filenames replace each other. Files in <filename>/etc</filename>
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have the highest priority and take precedence over files with the same
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name in <filename>/usr/lib</filename>. This can be used to override a
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system-supplied hwdb file with a local file if needed;
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a symlink in <filename>/etc</filename> with the same name as a hwdb file in
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<filename>/usr/lib</filename>, pointing to <filename>/dev/null</filename>,
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disables that hwdb file entirely. hwdb files must have the extension
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<filename>.hwdb</filename>; other extensions are ignored.</para>
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<para>Each hwdb file contains data records consisting of matches and associated
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key-value pairs. Every record in the hwdb starts with one or more match strings,
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specifying a shell glob to compare the lookup string against. Multiple match lines
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are specified in consecutive lines. Every match line is compared individually, and
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they are combined by OR. Every match line must start at the first character of the
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line.</para>
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<para>The match lines are followed by one or more key-value pair lines, which are
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recognized by a leading space character. The key name and value are separated by
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<literal>=</literal>. An empty line signifies the end of a record. Lines beginning
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with <literal>#</literal> are ignored.</para>
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<para>In case multiple records match a given lookup string, the key-value pairs
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from all records are combined. If a key is specified multiple times, the value
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from the record with the highest priority is used (each key can have only a single
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value). The priority is higher when the record is in a file that sorts later
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lexicographically, and in case of records in the same file, later records have
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higher priority.</para>
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<para>The content of all hwdb files is read by
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<citerefentry><refentrytitle>systemd-hwdb</refentrytitle><manvolnum>8</manvolnum></citerefentry>
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and compiled to a binary database located at <filename>/etc/udev/hwdb.bin</filename>,
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or alternatively <filename>/usr/lib/udev/hwdb.bin</filename> if you want ship the
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compiled database in an immutable image. During runtime, only the binary database
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is used.</para>
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</refsect1>
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<refsect1>
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<title>Examples</title>
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<example>
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<title>General syntax of hwdb files</title>
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<programlisting># /usr/lib/udev/hwdb.d/example.hwdb
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# Comments can be placed before any records. This is a good spot
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# to describe what that file is used for, what kind of properties
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# it defines, and the ordering convention.
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# A record with three matches and one property
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mouse:*:name:*Trackball*:
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mouse:*:name:*trackball*:
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mouse:*:name:*TrackBall*:
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ID_INPUT_TRACKBALL=1
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# A record with a single match and five properties
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mouse:usb:v046dp4041:name:Logitech MX Master:
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MOUSE_DPI=1000@166
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MOUSE_WHEEL_CLICK_ANGLE=15
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MOUSE_WHEEL_CLICK_ANGLE_HORIZONTAL=26
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MOUSE_WHEEL_CLICK_COUNT=24
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MOUSE_WHEEL_CLICK_COUNT_HORIZONTAL=14
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</programlisting>
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</example>
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<example>
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<title>Overriding of properties</title>
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<programlisting># /usr/lib/udev/hwdb.d/60-keyboard.hwdb
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evdev:atkbd:dmi:bvn*:bvr*:bd*:svnAcer*:pn*
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KEYBOARD_KEY_a1=help
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KEYBOARD_KEY_a2=setup
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KEYBOARD_KEY_a3=battery
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evdev:atkbd:dmi:bvn*:bvr*:bd*:svnAcer*:pn123*
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KEYBOARD_KEY_a2=wlan
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# /etc/udev/hwdb.d/70-keyboard.hwdb
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# disable wlan key on all at keyboards
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evdev:atkbd:*
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KEYBOARD_KEY_a2=reserved</programlisting>
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<para>If the hwdb consists of those two files, a keyboard with the lookup string
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<literal>evdev:atkbd:dmi:bvnAcer:bdXXXXX:bd08/05/2010:svnAcer:pn123</literal>
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will match all three records, and end up with the following properties:</para>
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<programlisting>KEYBOARD_KEY_a1=help
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KEYBOARD_KEY_a2=reserved
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KEYBOARD_KEY_a3=battery</programlisting>
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</example>
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</refsect1>
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<refsect1>
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<title>See Also</title>
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<para>
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<citerefentry>
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<refentrytitle>systemd-hwdb</refentrytitle><manvolnum>8</manvolnum>
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</citerefentry>
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</para>
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</refsect1>
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</refentry>
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