I have a Toshiba l755 laptop, and I installed 12.04 64bit on it. The default brightness of the laptop is set to maximum value, and I can't change it.
If I go to Configuration → Brightness, the brightness doesn't change and neither does pressing the function keys.
I tried changing some parameters of grub file, setting
GRUB_CMDLINE_LINUX_DEFAULT="quiet splash acpi_osi=Linux acpi_backlight=vendor".
When changing the brightness from configuration, the value of
/sys/class/backlight/toshiba/brightess changes, but screen remains the same. If I use the key functions, it changes the "actual_brightness" files. I don't know what else can I do, any suggestions?