[Bug 12637] Re: LCD Brightness on Laptop Always Set Very Low at Boot
mjulier at free.fr
Sun Jun 29 20:38:27 UTC 2008
I struggled with the same problem, before making my own workaround: screen would sometimes dim
- after install,
- at boot (but tends to improve with boot number: I even thought it was fixed, 1 month without trouble, and then back again),
- after using Windows Vista,
- when gdm starts,
- when VLC starts playing a video
- after running "xset dpms force off; sleep 1; xset dpms force on"
- after closing/opening lid (this is corrected is set "do nothing" on lid closing; it still switch off the screen though)
When logged in, I could correct the brightness using Fn-F5 (darker) or
Fn-F6 (brighter), or 2 times Fn-F7 (LCD OFF/ON). When in GDM or in
console mode, the only key that works is 2 times Fn-F7 (LCD OFF/ON).
I could find no real "good" solution, but I made a perfect (but ugly)
workaround, which stills allows me to adjust the brightness, and even
still adjusts the brightness on (dis)connecting the AC cord.
I found that the brightness value is stored in
/sys/devices/virtual/backlight/asus-laptop/brightness (in my case),
that the value is correct even when the actual brightness is wrong, and
that it is corrected if I rewrite the same value in the same file. So I
launch a program that precisely does that every second.
So my workaround is the following:
In /etc/rc.local, add this line before "exit 0":
And in this file, copy this (adjust "FILE=" as necessary):
if ps -e | grep $COMMAND | grep -v $PID > /dev/null; then
echo "Program $COMMAND already running, not launching again"
while true; do
echo "$a" > "$FILE"
Linux 2.6.24-19-generic #1 SMP
Ubuntu 8.04 LTS
Laptop: ASUS M51L
LCD Brightness on Laptop Always Set Very Low at Boot
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