linux-kernel - Re: [PATCH] samsung-laptop: unregister ACPI video module for some well known laptops

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Message-ID: <CAHR064hagc7s19fn=bF90WXvnrdT=yh_vTDcMmf3aKdaL66HnQ@mail.gmail.com>
Date:	Tue, 17 Apr 2012 10:31:44 +0200
From:	Corentin Chary <corentin.chary@...il.com>
To:	Matthew Garrett <mjg59@...f.ucam.org>,
	Corentin Chary <corentin.chary@...il.com>,
	platform-driver-x86@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux acpi <linux-acpi@...r.kernel.org>,
	Len Brown <len.brown@...el.com>
Subject: Re: [PATCH] samsung-laptop: unregister ACPI video module for some
 well known laptops

On Fri, Apr 6, 2012 at 4:34 PM, Seth Forshee <seth.forshee@...onical.com> wrote:
> On Fri, Apr 06, 2012 at 11:42:18AM +0200, Corentin Chary wrote:
>> On Tue, Mar 27, 2012 at 1:21 PM, Matthew Garrett <mjg59@...f.ucam.org> wrote:
>> > On Tue, Mar 27, 2012 at 11:11:18AM +0200, Corentin Chary wrote:
>> >> Matthew, is this one ok ? I really hope this patch can go in 3.4 so we
>> >> don't introduce a regression for old laptops.
>> >
>> > Yes, I've got this now.
>> >
>> > Thanks,
>>
>>
>> A user just found a DSDT which is broken by this way of doing things
>> (this is not really a regression since it was also broken before).
>>
>> _BCL contains a wierd "Or (VDRV, 0x02, VDRV)".
>> So if you call _BLC once (video.ko will), it set a flag that affect
>> the behavior of all backlight related stuff, and it breaks
>> samsung-laptop's backlight even if samsung-laptop unload the acpi
>> backlight.
>> Using acpi_backlight=vendor solves that since it prevents the module
>> from being loaded. My previous patch also fix that since it use
>> acpi_backlight= mechanism.
>>
>> Do you think using acpi_backlight=vendor is a good enought solution
>> here ? Should we use my first patch instead ?
>
> I've recently noticed another problem with using acpi_video_unregister()
> to disable known broken backlights -- another module might call
> acpi_video_register() and make it reappear. i915 does this, so when I
> EFI boot the MacBook Pro 8,2 the acpi backlights reappear (under a BIOS
> compatible boot the Intel GPU doesn't show up on the bus).
>
> So Corentin's solution does seem like a better way to go, or else
> something similar that forces the ACPI video driver to behave as with
> acpi_video=vendor.
>
> Seth
>

Matthew, Len, any input on that ? Should we keep the current code even
if broken with some (also broken) hardware or should we move the
blacklist in acpi/video.c ?


-- 
Corentin Chary
http://xf.iksaif.net
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