Brightness doesn't work using acpi from video driver

[Lucazade]

Brightness doesn't work using acpi from video driver with default kernel option "acpi_backlight=video"

Using kernel option "acpi_backlight=vendor" this allow vendor acpi driver to control brightness hotkeys.
reported to work with Dell Mini and Asus EEEPC (eeepc-wmi and dell_backlight modules) but this doens't work with acer-wmi.
"ls /sys/class/backlight" shows these modules.

Swithching off "acpi=off" fixes brightness issue but it is not recommended to disable acpi.

The strange thing is that kernel 2.6.38 has a stub gpu module (called poulsbo) that should call "acpi_video_register()" and fix
 "acpi_backlight=video" for all vendors.. but unfortunately doesn't seem to work.

[Lucazade (lucazade)]

"Currently, there have no GMA500(Poulsbo) native video driver to support
intel opregion. So, use this stub driver to enable the acpi backlight
control sysfs entry files by requrest acpi_video_register."

https://patchwork.kernel.org/patch/267421/