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

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Message-ID: <CACxGe6tK85FgYAT-1JQbLxEhRS34v2MPsx8urXADi6v2FnQ2gw@mail.gmail.com>
Date:	Wed, 29 Feb 2012 15:23:20 -0600
From:	Grant Likely <grant.likely@...retlab.ca>
To:	Grant Likely <grant.likely@...retlab.ca>,
	Matthew Garrett <mjg@...hat.com>,
	platform-driver-x86@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] platform/x86: Add driver for Apple gmux device

On Wed, Feb 29, 2012 at 1:50 PM, Seth Forshee
<seth.forshee@...onical.com> wrote:
> On Wed, Feb 29, 2012 at 12:43:23PM -0600, Grant Likely wrote:
>> On Wed, Feb 29, 2012 at 11:53 AM, Seth Forshee
>> <seth.forshee@...onical.com> wrote:
>> > On Wed, Feb 29, 2012 at 11:46:39AM -0600, Grant Likely wrote:
>> >> On Wed, Feb 22, 2012 at 8:37 AM, Seth Forshee
>> >> <seth.forshee@...onical.com> wrote:
>> >> > Apple laptops with hybrid graphics have a device named gmux that
>> >> > controls the muxing of the LVDS panel between the GPUs as well as screen
>> >> > brightness. This driver adds support for the gmux device. Only backlight
>> >> > control is supported initially.
>> >> >
>> >> > Signed-off-by: Seth Forshee <seth.forshee@...onical.com>
>> >>
>> >> Works for me.
>> >>
>> >> Tested-by: Grant Likely <grant.likely@...retlab.ca>
>> >>
>> >> Now I just need to figure out how to get the desktop backlight widget
>> >> to use gmux_backlight instead of acpi_video0...
>> >
>> > The easy way is to pass acpi_backlight=vendor to the kernel, then you
>> > won't have acpi_vidoe0.
>>
>> That did it, thanks.  I'm assume something is in the works to set it
>> up automatically?
>
> Not that I'm aware of. A number machines have this problem, that the
> standard ACPI backlight interfaces are implemented but don't work. This
> generally isn't detectable in software; with the Apples at least
> everything looks like it's working except that the brightness doesn't
> change (but not all Apple laptops are affected, so qurking based on
> manufacturer wouldn't work). All we're left with is DMI quirking, which
> isn't practical. Maybe we could add something so a platform driver can
> tell acpi_video that it knows the ACPI backlight doesn't work, but I
> think on some platforms that still is going to be based off of DMI
> information.

blacklisting based on specific product name (ie. MacBookPro8,*) or
machine model is probably the best.  It wouldn't be the first
blacklist in the linux kernel.

g.
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