[331.20] Backlight on Toshiba Qosmio X770 max. Brightness only at 70%

Since I’ve upgraded from 319.60 to 331.20 the backlight-intensity from my Qosmio X770 could only set to approx 70% of its original intensity.
Setting the backlight intensity darker is working but if I set it to 100% it’s only approx 70% of its original.

I’ve tested the kernel-param. acpi_backlight=vendor then the intensity is staying at 100% but at the end I can’t control the backlight.
(I’ve tested the acpi-Parameter too, but nothing gonna change)

It seems the NVidia-Driver 331.20 is using the ACPI-Table to get the max brightness, but the 319.60 don’t.
It would be nice if there is an option to disable the function for using the ACPI-Table or there is a solution to get the driver working without the disadvantage, because playing at 70% brightness from the backlight isn’t very funny and working with it is like sittin’ in a darkroom ;)

Ps.: I have the same strange behavior under windows, but i don’t care about cuz I’m not using this system very often.
The nouveau works correct… but the nouveu is no option for me.

It’s nice to see someone with the same problem I have on a similar toshiba laptop. Please see my thread: https://devtalk.nvidia.com/default/topic/552359/xrandr-brightness-is-incorrect-for-drivers-after-304-64-for-geforce-330m/.