linux-kernel - Re: [PATCH 3/5] gma500: backlight warning

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Date:	Wed, 13 Apr 2011 14:23:47 +0100
From:	Matthew Garrett <mjg59@...f.ucam.org>
To:	Alan Cox <alan@...rguk.ukuu.org.uk>
Cc:	Alan Cox <alan@...ux.jf.intel.com>, greg@...ah.com,
	linux-kernel@...r.kernel.org
Subject: Re: [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@...f.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@...f.ucam.org
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