linux-kernel - Re: [PATCH 0/3] Fix backlight issues on some Windows 8 systems

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Date:	Tue, 25 Jun 2013 18:10:35 +0200
From:	Daniel Vetter <daniel.vetter@...ll.ch>
To:	Matthew Garrett <mjg59@...f.ucam.org>
Cc:	Yves-Alexis Perez <corsac@...ian.org>, linux-acpi@...r.kernel.org,
	seth.forshee@...onical.com, joeyli.kernel@...il.com,
	intel-gfx <intel-gfx@...ts.freedesktop.org>,
	dri-devel <dri-devel@...ts.freedesktop.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Len Brown <lenb@...nel.org>, "Rafael J. Wysocki" <rjw@...k.pl>,
	Henrique de Moraes Holschuh <hmh@...ian.org>
Subject: Re: [PATCH 0/3] Fix backlight issues on some Windows 8 systems

On Tue, Jun 25, 2013 at 6:08 PM, Matthew Garrett <mjg59@...f.ucam.org> wrote:
> On Sat, Jun 22, 2013 at 11:46:39PM +0200, Yves-Alexis Perez wrote:
>
>> Before Linux support for acpi_osi("Windows 2012") (and when booting with
>> acpi_osi="!Windows 2012"), brightness keys were handled by the kernel
>> just fine, whether in console, in the display manager or in my desktop
>> environment (Xfce). xfce4-power-manager just needs to be told that the
>> brightness keys are already handled and it doesn't need to do anything.
>
> Right, the kernel has special-casing to hook the backlight keys up to
> the ACPI backlight control. This is an awful thing, because there's no
> way to detect this case other than parsing a single driver-specific
> module parameter.
>
> Could this functionality be duplicated across other backlight drivers?
> Not easily. The ACPI driver receives keypresses and performs backlight
> control. The i915 driver doesn't receive keypresses. We could easily tie
> certain keycodes into backlight events, but which backlight should they
> control? You're really starting to get into the kind of complex policy
> decision that's best left to userspace, which is where it should have
> been to begin with.

Do we have any chances to amend this mistake by (gradually) phasing
out support for the direct keypress forwarding in ACPI? Or at least
some plans?
-Daniel
--
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch
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