Fwd: Brightness on HP EliteBook 8460p

[Luca Tettamanti]

I'm putting back the CC and adding Alex.

On Tue, Jul 31, 2012 at 5:07 PM, Pali Rohár <pali.rohar at gmail.com> wrote:
> Thanks, now working. When I write to acpi video brightness file
> it change brightness and in dmesg is:
>
> [   47.200998] [drm:radeon_atif_handler], event, device_class =
> video, type = 0xd0
> [   47.201102] [drm:radeon_atif_get_sbios_requests], SBIOS
> pending requests: 0x80
> [   47.201104] [drm:radeon_atif_handler], ATIF: 1 pending SBIOS
> requests
> [   47.201105] [drm:radeon_atif_handler], Changing brightness to
> 11

Great! I'll send an updated patch to Alex soon.

> I think that acpi only sent event about brightness key pressed,
> because nothing happened when I pressed it.
>
> Also for windows is needed special HP application (hp hotkey) for
> brightness keys. Without it brightness keys not working too...

I've looked at hp-wmi: the hotkey is indeed dispatched via WMI
(hp-wmi) so you need something in userspace (KDE, Gnome, etc) to
respond to that key press.

> And there is one problem with /sys/class/backlight/radeon_bl.
> When I enable Ambient Light Sensor which auto adjust brightness
> based on sensor data, writing value 0 (min) or 255 (max) to
> /sys/class/backlight/radeon_bl/brightness turn off display.

Ok, that's weird. 0 turns off the panel by design, 255 should not...

> All
> other values (1-254) are OK (adjust brightness level). When I
> turn off Ambient Light Sensor (via hp-wmi kernel module) then
> values 0 and 255 also set brightness level (min and max). My
> suggestion is to convert value 0 to 1 and 255 to 254 to prevent
> this problem.

No idea what's going on here... might be some weird vendor magic.
The WMI code is rather obscure...

Luca