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

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Date:	Wed, 23 Nov 2011 12:30:12 -0800
From:	Greg KH <gregkh@...e.de>
To:	Corentin Chary <corentin.chary@...il.com>
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 Wed, Nov 23, 2011 at 07:58:20AM +0100, Corentin Chary wrote:
> 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).

That sounds reasonable.

thanks,

greg k-h
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