Re: [PATCH] xf86-video-intel: change order of DPMS operations

[Chris Wilson <chris@chris-wilson.co.uk>]

On Thu, 08 Dec 2011 08:35:12 -0800, Keith Packard <keithp@keithp.com> wrote:
> On Thu, 08 Dec 2011 14:10:06 +0000, Chris Wilson <chris@chris-wilson.co.uk> wrote:
> 
> > I had to remind myself why both the driver and the kernel are both
> > touching the backlight across DPMS; the answer as I see it is that the
> > kernel only knows about the raw backlight interface whereas the driver
> > adjusts it via the preferred interface (which should handle the cases
> > where the backlight modulation is handled independently of the PWM
> > registers).
> 
> Something in the kernel should be managing the backlight or we won't be
> doing this right when fbdev is running. User space should not have to
> know about the vagaries of the kernel backlight land.

The tricky part is figuring out the right interface to use. Matthew
was working upon such a mechanism to provide userspace with the ability
to actually find the backlight controller for a respective output, but I
don't believe there was ever a kernel API for i915 to call.
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre