inverted brightness for HP notebook

[olivier.fambon at free.fr]

Hi there,

$ lspci | grep VGA
00:02.0 VGA compatible controller: Intel Corporation ValleyView Gen7 (rev 0e)

$ sudo lspci -v -s 00:02
00:02.0 VGA compatible controller: Intel Corporation ValleyView Gen7 (rev 0e) (prog-if 00 [VGA controller])
	Subsystem: Hewlett-Packard Company Device 2213
	Flags: bus master, fast devsel, latency 0, IRQ 107
	Memory at 90000000 (32-bit, non-prefetchable) [size=4M]
	Memory at 80000000 (32-bit, prefetchable) [size=256M]
	I/O ports at 3050 [size=8]
	Expansion ROM at <unassigned> [disabled]
	Capabilities: [d0] Power Management version 2
	Capabilities: [90] MSI: Enable+ Count=1/1 Maskable- 64bit-
	Capabilities: [b0] Vendor Specific Information: Len=07 <?>
	Kernel driver in use: i915


=> requires the following to make brightness control keys work as expected

$ cat /etc/modprobe.d/i915.conf 
options i915 invert_brightness=1




tested on ubuntu 14.04 (with added xorg conf below)

$ cat /usr/share/X11/xorg.conf.d/20-intel.conf 
Section "Device"
        Identifier  "card0"
        Driver      "intel"
        Option      "Backlight"  "intel_backlight"
        BusID       "PCI:0:2:0"
EndSection


Note that the same brightness inversion happened also on ubuntu 14.10 (vanilla install, no xorg conf required)


Cheers,
Olivier.