Comment 185 for bug 1098216

It took me a while, but I just tested the patches on top on 3.8.2.

- brightness keys don't work in a tty or when no userspace daemon handles brightness
- evtest /dev/input/event4 (Video Bus) sees KEY_BRIGHTNESS{UP,DOWN}
- on Xfce with xfce4-power-manager default config
  - brightness is correctly changed when brightness keys are used,
  - 16 levels (with no smoothing) and OSD is behaving correctly

For comparison, on a 3.8.2 booted with acpi_osi="!Windows 2012" I get:

- brightness keys work in a tty or when no userspace daemon is running (16 levels, no smoothing)
- evtest /dev/input/event4 (Video Bus) sees KEY_BRIGHTNESS{UP,DOWN}
- on Xfce with xfce4-power-manager default config
  - brightness is correctly changed when brightness keys are used
  - I only get 9 levels, since brightness is changed both by the kernel and by xfpm
  - when disabling xfpm brightness keys handling I get 16 levels back (and I lose the OSD report)

In my opinion the second behavior is better since that means brightness doesn't depend on userspace. And I wonder if KEY_BRIGHTNESS{UP,DOWN} should be sent at all, since job has already been done.