linux-kernel - Re: [PATCH 03/15] samsung-laptop: don't handle backlight if handled by acpi/video

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Message-ID: <CAHR064jucMdu3KKctTTE=peNjhZ8TNvh6WecUrGc+HQp9BFpvg@mail.gmail.com>
Date:	Wed, 23 Nov 2011 07:58:20 +0100
From:	Corentin Chary <corentin.chary@...il.com>
To:	Greg KH <gregkh@...e.de>
Cc:	platform-driver-x86@...r.kernel.org,
	Matthew Garrett <mjg@...hat.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 03/15] samsung-laptop: don't handle backlight if handled
 by acpi/video

On Tue, Nov 22, 2011 at 11:16 PM, Greg KH <gregkh@...e.de> wrote:
> On Tue, Nov 22, 2011 at 11:02:34PM +0100, Corentin Chary wrote:
>> samsung-laptop is not at all related to ACPI, but since this interface
>> is not documented at all, and the driver has to use it at load to
>> understand how it works on the laptop, I think it's a good idea to
>> disable it if a better solution is available.
>
> I wish this would work, but on the machine that I had, there was a valid
> ACPI table for the video device, yet I was told to "ignore it, it
> doesn't work and use the sabi interface instead", so this patch would
> break that machine :(

Well, it's why acpi_backlight=vendor is here: to enable and use the
vendor backlight instead of using the standard ACPI interface.
And nowadays, even gpu drivers provide a backlight class (at least for
intel, nvidia/nouveau, and maybe radeon.

> We might want to trigger off of the machine type for this kind of
> thing, that's the only way I can see this working properly.

But, yes, this is a "regression". Maybe we should do that:
- enable the backlight by default for all SECLINUX models
- disable it by default for swsmi, but let the user be able to enable
it with acpi_backlight=vendor (this is what is done with this patch).




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