ACPI display brightness on Lenovo Thinkpad T430s

[Fekete Zoltán <fekete.zoltan%minux.hu@localhost>]

Hi There,

Please give me advice how to proceed in the topic below. I want to have 
the display brightness working.

I have traced the route of the brightness buttonpress (up or down) in 
the acpi subsystem in the kernel on my laptop. Everything seems to be 
alright. The driver takes the button press, translates into an acpi 
code, then it calls the acpi driver, which sends the code to the hardware.
The brightness of the display is not changing, however.

Does anybody know what to do?

Some additional things:
- The brightness can be set when I am in the bootloader. So, the 
hardware works.
- The power button does not react in NetBSD, too. It gets the 
buttonpress, but no action is done. Interestingly when I use the docking 
station's power button, the system shuts down properly.

My system:
NetBSD 9 stable, amd64
Lenovo ThinkPad T430s


Thank you in advance,

FeZ