bca81be775
On my computer, the minimum brightness enforced by clamping in backlight is too bright. Let udev property ID_BACKLIGHT_CLAMP control whether the brightness is clamped or not.
100 lines
4.1 KiB
XML
100 lines
4.1 KiB
XML
<?xml version="1.0"?>
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<!--*-nxml-*-->
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<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN" "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
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<!--
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This file is part of systemd.
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Copyright 2013 Lennart Poettering
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systemd is free software; you can redistribute it and/or modify it
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under the terms of the GNU Lesser General Public License as published by
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the Free Software Foundation; either version 2.1 of the License, or
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(at your option) any later version.
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systemd is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public License
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along with systemd; If not, see <http://www.gnu.org/licenses/>.
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-->
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<refentry id="systemd-backlight@.service" conditional='ENABLE_BACKLIGHT'>
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<refentryinfo>
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<title>systemd-backlight@.service</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>Lennart</firstname>
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<surname>Poettering</surname>
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<email>lennart@poettering.net</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>systemd-backlight@.service</refentrytitle>
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<manvolnum>8</manvolnum>
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</refmeta>
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<refnamediv>
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<refname>systemd-backlight@.service</refname>
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<refname>systemd-backlight</refname>
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<refpurpose>Load and save the display backlight brightness at boot and shutdown</refpurpose>
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</refnamediv>
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<refsynopsisdiv>
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<para><filename>systemd-backlight@.service</filename></para>
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<para><filename>/usr/lib/systemd/systemd-backlight</filename></para>
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</refsynopsisdiv>
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<refsect1>
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<title>Description</title>
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<para><filename>systemd-backlight@.service</filename>
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is a service that restores the display backlight
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brightness at early boot and saves it at shutdown. On
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disk, the backlight brightness is stored in
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<filename>/var/lib/systemd/backlight/</filename>. During
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loading, if udev property
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<option>ID_BACKLIGHT_CLAMP</option> is not set to
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false value, the brightness is clamped to a value of
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at least 1 or 5% of maximum brightness, whichever is
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greater. This restriction will be removed when the
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kernel allows user space to reliably set a brightness
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value which does not turn off the display.</para>
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</refsect1>
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<refsect1>
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<title>Kernel Command Line</title>
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<para><filename>systemd-backlight</filename> understands
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the following kernel command line parameter:</para>
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<variablelist class='kernel-commandline-options'>
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<varlistentry>
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<term><varname>systemd.restore_state=</varname></term>
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<listitem><para>Takes a boolean
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argument. Defaults to
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<literal>1</literal>. If
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<literal>0</literal>, does not restore
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the backlight settings on boot. However,
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settings will still be stored on shutdown.
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</para></listitem>
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</varlistentry>
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</variablelist>
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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><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>
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</para>
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</refsect1>
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</refentry>
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