[Intel-gfx] Legacy backlight control with KMS and BACKLIGHT property

[Jesse Barnes]

On Sun, 16 Aug 2009 15:11:07 -0700
Greg KH <greg at kroah.com> wrote:

> On Fri, Aug 14, 2009 at 10:16:06PM -0700, Jesse Barnes wrote:
> > On Fri, 14 Aug 2009 12:28:47 -0700
> > Greg KH <greg at kroah.com> wrote:
> > 
> > > On Fri, Aug 14, 2009 at 12:08:21PM -0700, Greg KH wrote:
> > > > Here's a first cut at such a driver.  It works for me on this
> > > > laptop, but note that it will try to work on _any_ Intel-based
> > > > system.  I'll figure out how to do this only for specific
> > > > machines based on DMI data next.
> > > 
> > > And here's one that is set for DMI data to only load on the proper
> > > ones.
> > > 
> > > I'll push this upstream now, if there are no objections.
> > 
> > Yeah, looks fairly reasonable.  This code should work on most
> > pre-965 chipsets too, since they share the LBB regs.  There are a
> > couple of other things to take into consideration: I think the
> > VBIOS indicates whether the controls are inverted (i.e. a value of
> > 0xff is minimum brightness) and there may also be some stepping
> > info.
> 
> Where can I find the register information so that I can properly read
> this kind of thing?

The best answer I have for this right now is
intel_bios.h/intel_bios.c.  I think the table type is documented in the
header, but we haven't written any code to get it out of the VBIOS in
intel_bios.c yet.

> 
> > So ultimately I'd like to see this be part of the i915 driver as
> > one of a few different methods supported (hopefully we can
> > autodetect them better than the 2D driver though, using the VBIOS
> > and DMI in the kernel).
> 
> That would be nice, I have no objection for that happening eventually.
> Feel free to take the driver and merge it into yours if you feel that
> is better.

Great, thanks a lot for putting this together Greg.


-- 
Jesse Barnes, Intel Open Source Technology Center