linux-kernel - Re: [PATCH 2/2] ACPI / video / i915: Remove ACPI backlight if firmware expects Windows 8

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Message-ID: <1378890565.4179.2.camel@oban>
Date:	Wed, 11 Sep 2013 11:09:25 +0200
From:	Yves-Alexis Perez <corsac@...ian.org>
To:	Matthew Garrett <matthew.garrett@...ula.com>
Cc:	Jani Nikula <jani.nikula@...ux.intel.com>,
	Aaron Lu <aaron.lu@...el.com>,
	"Rafael J. Wysocki" <rjw@...k.pl>, Daniel Vetter <daniel@...ll.ch>,
	ACPI Devel Mailing List <linux-acpi@...r.kernel.org>,
	Daniel Vetter <daniel.vetter@...ll.ch>,
	"intel-gfx@...ts.freedesktop.org" <intel-gfx@...ts.freedesktop.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
	Seth Forshee <seth.forshee@...onical.com>,
	"Lee, Chun-Yi" <joeyli.kernel@...il.com>,
	Igor Gnatenko <i.gnatenko.brain@...il.com>,
	Henrique de Moraes Holschuh <hmh@....eng.br>,
	Lee Chun-Yi <jlee@...ell.com>, Len Brown <lenb@...nel.org>
Subject: Re: [PATCH 2/2] ACPI / video / i915: Remove ACPI backlight if
 firmware expects Windows 8

On mer., 2013-09-11 at 08:45 +0000, Matthew Garrett wrote:
> On Wed, 2013-09-11 at 11:45 +0300, Jani Nikula wrote:
> 
> > Before plunging forward, have you observed any difference between the
> > boot modes? We have reports [1] that the backlight behaviour is
> > different with UEFI vs. UEFI+CSM or legacy boot. So I'm wondering if the
> > acpi_gbl_osi_data >= ACPI_OSI_WIN_8 check in patch 2/2 is the whole
> > story.
> > 
> > Further, if we tell the BIOS we're Windows 8 to use the tested BIOS code
> > paths, what guarantees do we have of UEFI+CSM or legacy boots working?
> 
> We have no evidence of Windows behaving differently based on the exposed
> firmware type.
> 
I do have an X230 which boots fine using pure UEFI or UEFI+CSM (and I
guess I can try booting it with a grml for pure legacy), so I can do
tests if needed.

Regards,
-- 
Yves-Alexis

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