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

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Message-ID: <CAMP44s1cLou9TMfLS+FHwPM_b3bG5HN1-hzgvhz0fVRCZ8XqWw@mail.gmail.com>
Date:	Wed, 31 Jul 2013 12:46:04 -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 9:00 AM, Matthew Garrett <mjg59@...f.ucam.org> wrote:
> On Wed, Jul 31, 2013 at 06:32:47AM -0500, Felipe Contreras wrote:
>> On Wed, Jul 31, 2013 at 12:14 AM, Matthew Garrett <mjg59@...f.ucam.org> wrote:
>> > 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.
>
> We aren't going to maintain a quirk list in order to support a guarantee
> that was never made. "0" as a backlight level has potentially meant
> "screen off" since the interface was first introduced.

That doesn't change the fact that you were wrong, and there *is*
actually a way. The fact that you don't want to go there doesn't mean
it's not there.

Here's another: device tree.

There are ways to provide a consistent backlight interface to user-space.

-- 
Felipe Contreras
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