Hi,
I'm facing a bug on a Samsung X20 notebook which features an i915 chipset (output of 'lspci -v' attached).
The effect is that setting the backlight to odd values causes the value to be misinterpreted. Harald Hoyer (cc:) had the same thing on a Netbook (I don't recall which model it was).
So this will turn the backlight to full brightness:
# cat /sys/class/backlight/intel_backlight/max_brightness 29750 # echo 29750 > /sys/class/backlight/intel_backlight/brightness
However, writing 29749 will turn the display backlight off, and 29748 appears to be the next valid lower value.
It seems like the IS_PINEVIEW() branch in drivers/gpu/drm/i915/intel_panel.c: intel_panel_actually_set_backlight() could do the right thing, but this code is written for an entirely different model, right?
I can reproduce this on 3.0 and 3.1 vanilla as well as with the current mainline git.
Let me know if there is any patch that I can test.
Thanks, Daniel