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Date: Wed, 31 Jul 2013 13:07:57 -0500
Message-ID: <CAMP44s1c5pmiC2fvmRi9vFrJXb2zYUT_F=paM2LR_V+7THnFVg@mail.gmail.com>
Subject: Re: [REGRESSION/PATCH] acpi: blacklist win8 OSI for ASUS Zenbok Prime UX31A
From: Felipe Contreras <felipe.contreras@gmail.com>
To: Matthew Garrett <mjg59@srcf.ucam.org>
Cc: "Rafael J. Wysocki" <rjw@sisk.pl>, Aaron Lu <aaron.lwe@gmail.com>,
        linux-kernel@vger.kernel.org, linux-acpi@vger.kernel.org,
        Len Brown <lenb@kernel.org>,
        Linus Torvalds <torvalds@linux-foundation.org>
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On Wed, Jul 31, 2013 at 12:52 PM, Matthew Garrett <mjg59@srcf.ucam.org> wrote:
> On Wed, Jul 31, 2013 at 12:46:04PM -0500, Felipe Contreras wrote:
>
>> 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.
>
> A quirk list will be incomplete, and as such there's no way to guarantee
> whether or not a value of 0 will turn off the backlight. This is why the
> interface doesn't make that guarantee, and why any userspace that
> depends upon that behaviour is behaving incorrectly.

There's no "guarantee" of anything. There is no "guarantee" that your
computer won't freeze when you boot Linux.

>> Here's another: device tree.
>
> There's no functional distinction between device tree and a quirk list
> on x86 - they're both static data sources provided by something other
> than the system firmware. As a result, they will both be incomplete.

So? If something can't be perfect that means we shouldn't even try?

If we can make the software behave consistently for 99% of the
machines out there instead of only 90%, that's better.

>> There are ways to provide a consistent backlight interface to user-space.
>
> No, there aren't.

Yes there are. Not perfectly, nothing is ever perfect, but there are ways.

-- 
Felipe Contreras
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