I added now an external monitor to the laptop so that I could investigate what
state its is in when booted withouth "acpi=off". It
turns out that with ACPI enabled, the xrandr brightness range is 0-9:
$ xrandr --prop
Screen 0: minimum 320 x 200, current 1024 x 768, maximum 8192 x 8192
LVDS1 connected 1024x768+0+0 (normal left inverted right x axis y axis) 344mm x
193mm
EDID:
00ffffffffffff000daf991500000000
07140103802213780a3d9594564f8e28
26505400000001010101010101010101
0101010101017a1d56d250001e303c28
360058c110000018000000fe004e3135
3642332d4c30420a2020000000fe0043
4d4f0a202020202020202020000000fe
004e31353642332d4c30420a20200048
BACKLIGHT: 9 (0x00000009) range: (0,9)
Backlight: 9 (0x00000009) range: (0,9)
However the commands dont make any difference, as brightness does not change
(screen stays almost black):
$ xrandr --output LVDS1 --set BACKLIGHT 0
$ xrandr --output LVDS1 --set BACKLIGHT 5
$ xrandr --output LVDS1 --set BACKLIGHT 9
lsmod shows that the module "acer_wmi" is loaded. Unloading it does not
make a difference. All hotkeys seem to work all the time.
The page http://www.mjmwired.net/kernel/Documentation/laptops/acer-wmi.txt says
there should be a directory /sys/devices/platform/acer-wmi/backlight/acer-wmi/,
but that does not exist on this machine:
/sys/devices/platform/acer-wmi$ ls
driver interface modalias power rfkill subsystem uevent
Playing around a little bit I noticed that in
sudo -s
echo "1" > /sys/class/backlight/intel_backlight/brightness
# makes the screen bright
echo "2948310" > /sys/class/backlight/intel_backlight/brightness
# makes the screen dark
I added the first line to /etc/rc.local and this works as a temporary
fix. The Fn+Arrow buttons however do not change the brightness.
--
You received this bug notification because you are a member of Ubuntu-X,
which is subscribed to xorg in Ubuntu.
https://bugs.launchpad.net/bugs/910536
Title:
Screen too dark, no backlight, unusable X
To manage notifications about this bug go to:
https://bugs.launchpad.net/ubuntu/+source/xorg/+bug/910536/+subscriptions
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