linux-kernel - Re: [PATCH v2] platform/x86: Add driver for Apple gmux device

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Date:	Mon, 12 Mar 2012 10:40:00 -0500
From:	Seth Forshee <seth.forshee@...onical.com>
To:	Matthew Garrett <mjg59@...f.ucam.org>
Cc:	platform-driver-x86@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] platform/x86: Add driver for Apple gmux device

On Mon, Mar 12, 2012 at 03:22:24PM +0000, Matthew Garrett wrote:
> On Mon, Mar 12, 2012 at 10:18:52AM -0500, Seth Forshee wrote:
> 
> > Why do you presume it works under Windows? Boot camp installs a pile of
> > drivers for Windows, one of those could be a driver for the backlight. I
> > don't know either way. But it's pretty clear that MacOS is using the
> > gmux for the backlight when it is present from the reverse engineering
> > work done by others.
> 
> The only reason to provide it at all is for Windows - it's never going 
> to be used under OS X.

I'm not so sure. The MacBook Pro 8,1 and 8,2 seem to use the same BIOS
implementation -- the version numbers and DSDTs are identical.  The 8,1
has only Intel graphics, no gmux, and a working acpi_video0 backlight
under Linux. The 8,2 has hybrid ATI/Intel, a gmux w/ working backlight
control, and acpi_video0 does not work.

So while I'm not sure, I can't rule out that the acpi_video backlight
might be provided specifically for the 8,1 and that OS X is using it.
Unfortunately I don't have an 8,1 that I can play with to try and work
it out.

Seth

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