Brightness adjustment keys <Fn + ⇑/⇓> have no effect (although they are recognized by the environment), and I can't change the brightness using GUI tools as well. This seems like a problem in Linux itself, not the desktop environment.
I can change the brightness in Windows OS, so it's not some kind of hardware fault.
Lenovo B570 (Model Name: 20093)
Integrated Intel HD graphics card
Kubuntu 11.04 (Linux 2.6.38-10-generic, KDE 4.7.0), everything up to date
No proprietary graphics drivers (only Wi-Fi one)
What I've tried:
nomodeset. And yes, I did
/etc/X11/xorg.conf(no such file, even after
sudo dpkg-reconfigure xserver-xorg)
/proc/acpi/video/VGA/LCD/brightness(no such file)
sudo setpci -s 00:02.0 F4.B=(no effect)
No outputs have backlight property")
How can I fix this issue?