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

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Message-ID: <CAMP44s3vT94+yS-UdO98ibQUZBiL=dQ22QFTM0H4bJLVxLpr1g@mail.gmail.com>
Date:	Fri, 2 Aug 2013 20:07:37 -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 8:16 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?

-- 
Felipe Contreras
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