On Sat, Aug 16, 2014 at 08:25:42PM +0200, Thomas Richter wrote:
> Hi Ville
> >> just testing your alm_fixes11 branch. So far, everything works fine,
> >> including suspend2ram, for the first time! Yippiee!
> >>
> >> However, there is one thing that bothers me, namely that the brightness
> >> adjustment is no longer working. Specifically, fujitsu_laptop fails with:
> >>
> >> Fujitsu laptop FUJ02B1 ACPI brightness driver: probe of FUJ02B1:00
> >> failed with error -22
> >
> > My impression was that those were happening since forever. But I can't
> > be sure.
> Actually, it did work with the alm-fixes5 patch, based on 3.15.0 rc7+ IIRC.
> >> The source of fujitsu_laptop does not seem to have changed, thus I
> >> believe it must be somehow related to the modifications you made. Any
> >> idea where to look?
> >
> > Hmm. My impression was that the backlight control is handled by some
> > hardware/firmware magic and OS can't touch it. IIRC that's how it seemed
> > to work on my 855 machine which is a slighly newer Fujitsu-Siemens
> > Lifebook model. At least on that machine backlight buttons worked
> > a while ago.
> Oh, sorry, I should have clarified. Yes, the *buttons* work, those are 
> handled by the firmware (via the Bios service management interrupt, I 
> suppose), but usually the fujitsu-laptop module *also* creates a device 
> which provides access to the brightness control such that tools like the 
> Gnome brightness applet can pick the information up and allows 
> user-control of the brightness. The corresponding device does no longer 
> exist on 3.16.0. Not yet fully clear whether that's due to the patches 
> you made or something else, but I was running out of time yesterday to 
> start a bisection, and I'm currently on the road and cannot test 
> (greetings from Newark airport, BTW.)

I would suggest it's some acpi change then. There was some change to
break the acpi video button stuff from acpi backlight driver, but I'm
not sure this would have affected fujitsu_laptop, and I'm not sure when
that went in. Might also be some other acpi patch. Not sure if just
looking at why/how it fails could pintpoint the problem or if bisecting
is the only reasonable option.

Ville Syrjälä
Intel OTC
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