linux-kernel - Re: [PATCH] acpi: video: fix reversed indexed BQC

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Message-ID: <51FB35CD.7040709@intel.com>
Date:	Fri, 02 Aug 2013 12:30:05 +0800
From:	Aaron Lu <aaron.lu@...el.com>
To:	Felipe Contreras <felipe.contreras@...il.com>
CC:	linux-kernel@...r.kernel.org, linux-acpi@...r.kernel.org,
	"Rafael J. Wysocki" <rjw@...k.pl>, Len Brown <lenb@...nel.org>,
	Zhang Rui <rui.zhang@...el.com>
Subject: Re: [PATCH] acpi: video: fix reversed indexed BQC

On 08/02/2013 12:11 PM, Felipe Contreras wrote:
> On Thu, Aug 1, 2013 at 9:03 PM, Aaron Lu <aaron.lwe@...il.com> wrote:
>> On 08/02/2013 07:34 AM, Felipe Contreras wrote:
>>> Commit 1a7c618 (ACPI video: support _BQC/_BCL/_BCM methods that use
>>> index values) assumed that bl->levels were not reverted, but at this
>>> point they already are, so there's no need to revert them yet again.
>>
>> When acpi_video_bqc_value_to_level is called, bl->levels is not
>> reverted.
> 
> This is the code that turns br->flags._BCL_reversed on:
> 
> 	if (max_level == br->levels[2]) {
> 		br->flags._BCL_reversed = 1;
> 		sort(&br->levels[2], count - 2, sizeof(br->levels[2]),
> 			acpi_video_cmp_level, NULL);
> 	}
> 
> Now tell me how br->flags._BCL_reversed can be on, and the br->levels
> *not* reverted.

Oh yes, it is reverted to be in increase order, so it is not in reverse
order. I'm a little confused by these words.

Please see acpi_video_bqc_quirk, we set _BQC_use_index by revert the
level on a reversed _BCL, so we will need to revert level here too.

-Aaron
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