xrandr --output LVDS --set BACKLIGHT 0
The command above will set the brightness to its maximum value, while the one below sets the minimum value:
xrandr --output LVDS --set BACKLIGHT 13
What kind of platform is it? Can you attach the output of "xrandr --prop", your X log and your xorg.conf file? Also, can you attach your VBIOS rom file?
$ cd cd /sys/devices/pci0000\:00/0000\:00\:02.0
$ echo 1 > rom
$ cat rom > /tmp/vbios.bin
$ echo 0 > rom
(you'll need to be root).
Created attachment 18454 [details]
Created attachment 18455 [details]
x.org log file
Created attachment 18456 [details]
Created attachment 18457 [details]
VBIOS rom file
This is the information given by lshal:
system.chassis.manufacturer = 'Packard Bell BV' (string)
system.chassis.type = 'Notebook' (string)
system.firmware.release_date = '05/11/2007' (string)
system.firmware.vendor = 'American Megatrends Inc.' (string)
system.firmware.version = '206' (string)
system.formfactor = 'laptop' (string)
system.hardware.primary_video.product = 10146 (0x27a2) (int)
system.hardware.primary_video.vendor = 32902 (0x8086) (int)
system.hardware.product = 'EasyNote_BU45' (string)
system.hardware.serial = '000613360386' (string)
system.hardware.uuid = 'DC8A0100-3432-0180-BF5A-001D60001558' (string)
system.hardware.vendor = 'Packard Bell BV' (string)
system.hardware.version = 'PB72E06210' (string)
system.kernel.machine = 'x86_64' (string)
system.kernel.name = 'Linux' (string)
system.kernel.version = '2.6.26-1-amd64' (string)
Ah, that's interesting. It looks like your system is probably using ACPI for backlight control (what does /sys/class/backlight contain?) but ACPI exposes an inverted scale to userspace. I would think that the kernel's backlight API should be semantically consistent, so we might need to fix this there...
$ ls /sys/class/backlight/
I'm using "video" module, if that is relevant. Do you think this may be the reason why this happens? But brightness control does not work without it :/
BTW, /proc/acpi/video/VGA/LCDD/brightness works correctly.
No, using the video module is the right thing to do. On many platforms, using ACPI is the only way we have of controlling the backlight. But on yours it seems that the ACPI video module exposes an inverted scale. I'd say that an ACPI video module bug, you should probably file a bug against the kernel ACPI stuff at bugzilla.kernel.org. If you do, please add the URL to this bug so we can close it and track the issue at kernel.org.
Added URL entry pointing to http://bugzilla.kernel.org/show_bug.cgi?id=11396
Ok, thanks. Sorry for punting you over there, but the ACPI guys are generally pretty responsive, so hopefully they'll fix your issue quickly.