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SubjectRe: [PATCH 3/5] gma500: backlight warning
On Wed, Apr 13, 2011 at 02:20:22PM +0100, Alan Cox wrote:
> On Wed, 13 Apr 2011 14:17:14 +0100
> Matthew Garrett <mjg59@srcf.ucam.org> wrote:
>
> > On Wed, Apr 13, 2011 at 10:36:19AM +0100, Alan Cox wrote:
> > > props.max_brightness = 100;
> > > + props.type = BACKLIGHT_PLATFORM;
> >
> > No, this should be BACKLIGHT_RAW - it's hitting the control registers
> > directly rather than going via a platform interface.
>
> Ah ok - I figured it *was* the platform backlight. I'll send Greg a new
> version of that changeset.

Platform is intended for cases where the platform (ie, the specific
instance of a GMA500-based system) provides its own mechanism, rather
than falling through to the raw register access. The idea is that
platform interfaces may keep track of other platform-level policy such
as ALS. Opregion potentially mitigates these problems, but I've still
seen some cases where the distinction matters.

--
Matthew Garrett | mjg59@srcf.ucam.org


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