r277959 breaks X display on IvyBridge mobile GT2 IG

[Michael Gmelin]

On Mon, 16 Feb 2015 15:45:46 -0800
Adrian Chadd <adrian at freebsd.org> wrote:

> On 16 February 2015 at 14:40, Ian FREISLICH <ianf at capeaugusta.com>
> wrote:
> > Ian FREISLICH wrote:
> >> Adrian Chadd wrote:
> >> > Hi,
> >> >
> >>
> >> > There's a "invert backlight" option in i915, try setting it to 1?
> >>
> >> This is pretty much all I could find (unless I was looking in the
> >> wrong place).  It makes no difference.  The backlight appears to
> >> be disabled.
> >
> > Adrian, do you have any idea how to fix the backlight for my laptop?
> > I ended up reversing out your change r277959 in my local copy to
> > make the backlight work again here.
> 
> Hi,
> 
> I don't, no. I haven't dug further into the i915 backlight control
> code because, well, a lot of changed in that update. The backlight
> code was in a lot of flux during the period of time kib chose to fast
> forward, so it's not unsurprising that it broke for some.
> 
> I think for now we'll need a quirk that can be added for each laptop
> we find with that particular behaviour. The real solution is to
> continue sliding i915 forward in time.
> 

In the meantime this workaround might be useful (not sure if it works
while the driver is loaded):

https://github.com/grembo/intel_backlight_fbsd


-- 
Michael Gmelin