linux-kernel - Re: [REGRESSION/PATCH] acpi: blacklist win8 OSI for ASUS Zenbok Prime UX31A

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Date:	Wed, 31 Jul 2013 06:32:47 -0500
From:	Felipe Contreras <felipe.contreras@...il.com>
To:	Matthew Garrett <mjg59@...f.ucam.org>
Cc:	"Rafael J. Wysocki" <rjw@...k.pl>, Aaron Lu <aaron.lwe@...il.com>,
	linux-kernel@...r.kernel.org, linux-acpi@...r.kernel.org,
	Len Brown <lenb@...nel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [REGRESSION/PATCH] acpi: blacklist win8 OSI for ASUS Zenbok Prime UX31A

On Wed, Jul 31, 2013 at 12:14 AM, Matthew Garrett <mjg59@...f.ucam.org> wrote:
> On Tue, Jul 30, 2013 at 07:11:06PM -0500, Felipe Contreras wrote:
>
>> No, the ACPI driver is exposing a backlight interface, which has a
>> defined stable API.
>
> From the ACPI spec:
>
> 'The OEM may define the number 0 as "Zero brightness" that can mean to
> turn off the lighting (e.g. LCD panel backlight) in the device.'
>
> There's no mechanism for an OS to know whether or not a firmware
> implementation will actually turn the backlight off at 0, so there's no
> way the OS can define the lowest backlight state as anything other than
> "May or may not turn the screen off".

Yes there is; quirks.

-- 
Felipe Contreras
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