i965GM: Backlight controls do not work

[nephele]

I have a lenovo laptop with an integrated gpu, it seems to be picked up by the intel driver and exposes a backlight control, it does not do anything however. It is slightly annoying because the backlight is stuck on a small brightness.

hrev55910

[korli]

hi nephele, could you try with ​https://review.haiku-os.org/c/haiku/+/5190 ? It should be soon available at ​https://haiku.movingborders.es/testbuild/ if you need.

[korli]

Forget it, it probably wouldn't affect much as this is on Gen4.

[nephele]

Your review mentions gen 4 though? In any case I'm happy to test if you have a new review.

[korli]

It looks like i965 has a "combination_mode" flag, which indicates the use of the pci config register LBPC (0xf4) as multiplicator. The duty is multiplied by the value of the LBPC register.

A bit of documentation on ​https://01.org/sites/default/files/documentation/965_g35_vol_1_graphics_core.pdf

Legacy Backlight Brightness (LBES): The value of zero is the lowest
brightness setting and 255 is the brightest.

you could check the flag is present and the pci config register value.

[korli]

proposed change: ​https://review.haiku-os.org/c/haiku/+/5227

[korli]

Test images: ​https://haiku.movingborders.es/testbuild/Id591372475b969020af7428e09c116712014a4d6/1/hrev56040/

[nephele]

No change in behaviour (Picked the packages from your link in the x86_gcc2 directory) Test image: hrev56040_5227_1

[nephele]

New system log with 5227 applied

[nephele]

Hey korli, do you need more info? perhaps a more recent system log with the latch attached?