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

[Mike Lothian]

2009/8/15 Jesse Barnes <jbarnes at virtuousgeek.org>:
> 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.
>
> 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).
>
> The other three methods that need to export sysfs interfaces are
> OpRegion (already done), i2c (some machines have external controllers;
> the VBIOS describes how to interact with them) and PWM (the "native"
> power modulation regs).

This is great news guys, hopefully I'll finally be able to control the
screen brightness of my GM45 in my Samsung R510

If you want a guinea pig to test your code please feel free to forward patches

Cheers

Mike