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

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Date:	Mon, 9 Sep 2013 15:38:46 +0000
From:	Matthew Garrett <matthew.garrett@...ula.com>
To:	Daniel Vetter <daniel@...ll.ch>
CC:	"Rafael J. Wysocki" <rjw@...k.pl>, Aaron Lu <aaron.lu@...el.com>,
	"ACPI Devel Mailing List" <linux-acpi@...r.kernel.org>,
	Seth Forshee <seth.forshee@...onical.com>,
	"Lee, Chun-Yi" <joeyli.kernel@...il.com>,
	Daniel Vetter <daniel.vetter@...ll.ch>,
	"intel-gfx@...ts.freedesktop.org" <intel-gfx@...ts.freedesktop.org>,
	"dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Len Brown <lenb@...nel.org>,
	Igor Gnatenko <i.gnatenko.brain@...il.com>,
	Yves-Alexis Perez <corsac@...ian.org>,
	"Felipe Contreras" <felipe.contreras@...il.com>,
	Lee Chun-Yi <jlee@...ell.com>,
	Henrique de Moraes Holschuh <hmh@....eng.br>
Subject: Re: [PATCH 2/2] ACPI / video / i915: Remove ACPI backlight if
 firmware expects Windows 8

On Mon, 2013-09-09 at 17:21 +0200, Daniel Vetter wrote:

> If Win8 is as broken as we are I'm ok with the module option. It just
> sounded to me like right now we don't know of a way to make all machines
> somewhat happy, combined with the other pile of random backlight issues
> the assumption that we do something (maybe something a bit racy) that
> windows doesn't do isn't too far-fetched. So I'm not wary of the machines
> where the aml is busted for acpi_os=win8, but for the others where this
> broke stuff.

Windows 8 isn't broken because (as far as we can tell) the Intel drivers
under Windows 8 never use the ACPI backlight set function. Of course, it
would be nice to have that confirmed by Intel.

-- 
Matthew Garrett <matthew.garrett@...ula.com>