Created

Embed URL

HTTPS clone URL

SSH clone URL

You can clone with HTTPS or SSH.

Download Gist

For i915 systems with broken ACPI backlight controls, synchronize the ACPI value with the native control

View sync-acpi-intel.sh
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59
#!/bin/bash
# Copyright (c) 2011, Michel Alexandre Salim <salimma@fedoraproject.org>
# Permission is hereby granted, without written agreement and without
# license or royalty fees, to use, copy, modify, and distribute this
# software and its documentation for any purpose, provided that the
# above copyright notice and the following two paragraphs appear in
# all copies of this software.
#
# IN NO EVENT SHALL THE COPYRIGHT HOLDER BE LIABLE TO ANY PARTY FOR
# DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES
# ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS DOCUMENTATION, EVEN
# IF THE COPYRIGHT HOLDER HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH
# DAMAGE.
#
# THE COPYRIGHT HOLDER SPECIFICALLY DISCLAIMS ANY WARRANTIES, INCLUDING,
# BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
# FITNESS FOR A PARTICULAR PURPOSE. THE SOFTWARE PROVIDED HEREUNDER IS
# ON AN "AS IS" BASIS, AND THE COPYRIGHT HOLDER HAS NO OBLIGATION TO
# PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS.
 
BACKLIGHT_DIR=/sys/class/backlight
ACPI=${BACKLIGHT_DIR}/acpi_video0
INTEL=${BACKLIGHT_DIR}/intel_backlight
 
ACPI_MAX=`cat ${ACPI}/max_brightness`
INTEL_MAX=`cat ${INTEL}/max_brightness`
# this is about 500
#MULTIPLIER=$((INTEL_MAX/(ACPI_MAX+1)))
MULTIPLIER=500
MIN_BRIGHTNESS=$((INTEL_MAX-(MULTIPLIER*ACPI_MAX)))
 
function fib {
let a=$1
let b=$2
let n=$3
 
if [ $n == 0 ]; then
INTEL_BRIGHTNESS=$a
else
fib $b $((a + b)) $((n-1))
fi
}
 
while inotifywait -e modify ${ACPI}/brightness >/dev/null 2>&1; do
BRIGHTNESS=`cat ${ACPI}/brightness`
# specially handle maximum value
if [ ${BRIGHTNESS} == ${ACPI_MAX} ]; then
INTEL_BRIGHTNESS=$INTEL_MAX
else
# arithmetic
INTEL_BRIGHTNESS=$((MULTIPLIER*(BRIGHTNESS+1)))
# geometric
#INTEL_BRIGHTNESS=$((INTEL_MAX >> (8-BRIGHTNESS)))
#INTEL_BRIGHTNESS=$((25 << BRIGHTNESS))
#fibonacci
#fib 100 200 $(BRIGHTNESS)
fi
echo ${INTEL_BRIGHTNESS} > ${INTEL}/brightness
done

Thanks for this, Michel. I found it very useful while seeking a way to get backlight control to work on my new computer! :-) Fran├žois

Great! Thank you very much.
Note for Fedora users: you may need to install inotify-tools for inotifywait command to work.

Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment
Something went wrong with that request. Please try again.