linux-kernel - Re: [PATCH] acpi: video: improve quirk check

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Message-ID: <CAMP44s3a0fn3F6zch9LOB2XQrazQNU9NGejH4uUc2xiseysj=Q@mail.gmail.com>
Date:	Fri, 2 Aug 2013 20:30:16 -0500
From:	Felipe Contreras <felipe.contreras@...il.com>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
Cc:	Aaron Lu <aaron.lwe@...il.com>, linux-kernel@...r.kernel.org,
	linux-acpi@...r.kernel.org, Len Brown <lenb@...nel.org>,
	Zhang Rui <rui.zhang@...el.com>
Subject: Re: [PATCH] acpi: video: improve quirk check

On Fri, Aug 2, 2013 at 8:19 PM, Rafael J. Wysocki <rjw@...k.pl> wrote:
> On Friday, August 02, 2013 08:07:37 PM Felipe Contreras wrote:
>> On Fri, Aug 2, 2013 at 8:16 PM, Rafael J. Wysocki <rjw@...k.pl> wrote:
>> > On Friday, August 02, 2013 08:04:52 PM Felipe Contreras wrote:
>> >> On Fri, Aug 2, 2013 at 6:47 PM, Rafael J. Wysocki <rjw@...k.pl> wrote:
>> >> > On Friday, August 02, 2013 02:37:09 PM Felipe Contreras wrote:
>> >> >> If the _BCL package is descending, the first level (br->levels[2]) will
>> >> >> be 0, and if the number of levels matches the number of steps, we might
>> >> >> confuse a returned level to mean the index.
>> >> >>
>> >> >> For example:
>> >> >>
>> >> >>   current_level = max_level = 100
>> >> >>   test_level = 0
>> >> >>   returned level = 100
>> >> >>
>> >> >> In this case 100 means the level, not the index, and _BCM failed. But if
>> >> >> the _BCL package is descending, the index of level 0 is also 100, so we
>> >> >> assume _BQC is indexed, when it's not.
>> >> >>
>> >> >> This causes all _BQC calls to return bogus values causing weird behavior
>> >> >> from the user's perspective. For example: xbacklight -set 10; xbacklight
>> >> >> -set 20; would flash to 90% and then slowly down to the desired level
>> >> >> (20).
>> >> >>
>> >> >> The solution is simple; test anything other than the first level (e.g.
>> >> >> 1).
>> >> >>
>> >> >> Signed-off-by: Felipe Contreras <felipe.contreras@...il.com>
>> >> >
>> >> > Looks reasonable.
>> >> >
>> >> > Aaron, what do you think?
>> >>
>> >> Aaron has a similar patch does many more checks. I think we should add
>> >> more checks, but I think those should go into a separate patch.
>> >>
>> >> This patch alone fixes a real problem, which is rather urgent to fix,
>> >> and I did it this way so it's trivial to review and merge.
>> >
>> > And I still would like to know the Aaron's opinion, what's wrong with that?
>>
>> Nothing. What's wrong with my clarification?
>
> You're not Aaron. :-)

I can clarify and comment without your permission. All you can do is
disregard my comments, but others might find them useful, including
Aaron.

-- 
Felipe Contreras
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