Automatically reduce brightness
Contents
The idea
When watching someone working with an iBook I noticed that the brightness automatically faded to the lowest level after a few seconds of inactivity. I think that this is a simple way to save power. I wrote a c-daemon which uses the XScreenSaver extension to check whether the user is active. If he is not, it lowers the brightness to a specific level. When he is active again, the brightness is reset to the previous level.
Prerequisites
A recent kernel with the ibm-acpi driver (You should have a directory called /sys/class/backlight/ibm/).
Installation
- Download the brightness control daemon
- Unpack it and chdir into the brightd directory
- Call
$ make
- Move the brightd executable into a directory like /usr/local/bin
- Put
$ brightd -d
into your ~/.Xsession (or another distro-specific startup script) - Change the permissions of /sys/class/backlight/ibm/brightness so that your user can write to that file
See the README for more detailled instructions and command line parameters.
Example installation for Gentoo linux and XFCE4
$ wget -o /dev/null -O brightd-0.1.tar.bz2 "http://www.pberndt.com/Programme/Linux/brightd/_download/brightd-0.1.tar.bz2?ct=raw&sub=att" $ tar xjf brightd-0.1.tar.bz2 $ cd brightd-0.1/ $ make gcc -lX11 -lXss -o brightd brightd.c $ cp brightd /usr/local/bin/ $ cd /etc/xdg/xfce4 $ vi xinitrc 73Gi /usr/local/bin/brightd -s 5 -w 2 -d <escape>:x $ cd /etc/init.d/ $ cat > permissions start() { ebegin "Setting permissions on /sys" chmod g+w /sys/class/backlight/ibm/brightness chgrp wheel /sys/class/backlight/ibm/brightness eend $? } $ chmod a+x permissions $ rc-update add permissions boot $ ./permissions start
Done. Restart X to see it working.
Example installation for Debian Sid
brightd isn't yet in the official Debian archives (an ITP was filled), but you can get precompiled binaries for unstable from Zhenech's page.
$ wget http://debian.die-welt.net/pool/main/brightd/brightd_0.1-1_i386.deb
# dpkg -i brightd_0.1-1_i386.deb
Done. Relogin into your X session and brightd will be started. You can change this and other settings by editing /etc/default/brightd.
Possible problems
brightd does not fade, screensaver deactivated
On my Debian Sid box, brightd can run for hours and just do nothing. This happens because it thinks the screensaver is deactivated and screen shouldn't be faded (useful while watching videos). But in fact the screensaver isn't deactivated. To solve this problem, just execute the following command before starting bright:
$ xset s default
brightd says it is fading, but does not
On my Z61m /sys/class/backlight/ibm/brightness is 0 after the laptop boots up. As long it is 0, brightd does nothing, because it thinks, brightness is already as low as possible, so I need to initialize the brightness-level before using brightd:
# echo 7>/sys/class/backlight/ibm/brightness