Automatically reduce brightness

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 IBM ACPI extensions. (You should have a directory called /sys/class/backlight/ibm/)

Installation

1. Download the brightness control daemon
2. Unpack it and chdir into the brightd directory
3. Call $ make
4. Move the brightd executable into a directory like /usr/local/bin
5. Put $ brightd -d into your ~/.Xsession (or another distro-specific startup script)
6. 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 /proc"

        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_0.0.20070226-1_i386.deb

# dpkg -i brightd_0.0.20070226-1_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.

NOTE!

Changing permissions is not needed, because the binary is installed suid-root.