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Date: Wed, 15 Apr 2009 21:01:25 +0100
From: Matthew Garrett <mjg59@srcf.ucam.org>
To: Niel Lambrechts <niel.lambrechts@gmail.com>
Cc: Henrique de Moraes Holschuh <hmh@hmh.eng.br>,
       yakui_zhao <yakui.zhao@intel.com>,
       Andrew Morton <akpm@linux-foundation.org>,
       "linux.kernel" <linux-kernel@vger.kernel.org>,
       "linux-acpi@vger.kernel.org" <linux-acpi@vger.kernel.org>
Subject: Re: 2.6.30-rc1 (latest git): thinkpad-acpi: cannot control brightness with hotkeys (BISECTED)
Message-ID: <20090415200125.GA31483@srcf.ucam.org>
References: <49E10684.5090101@gmail.com> <20090411150555.8b13ed18.akpm@linux-foundation.org> <20090412161448.GC26502@khazad-dum.debian.net> <49E234ED.5010105@gmail.com> <1239585695.5564.5.camel@localhost.localdomain> <49E3575A.60204@gmail.com> <20090413203450.GC16152@khazad-dum.debian.net> <49E5234E.5070303@gmail.com> <20090415164939.GA27807@srcf.ucam.org> <49E63BCB.9090801@gmail.com>
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On Wed, Apr 15, 2009 at 09:55:55PM +0200, Niel Lambrechts wrote:

> The behaviour seems slightly different from before your 74a365b3f354
> commit in that /sys/class/backlight remains empty until i915 gets loaded
> for the first time, the contents then persist even if i915 is unloaded.
> Perhaps the directory was populated by a different kernel module, since
> when I did the bisect yesterday the directory would be there on boot
> before I started X or loaded i915.

In the past the directory would be created when the acpi video driver 
was loaded, but probably wouldn't work. Doing it that way is a violation 
of the opregion spec and causes some machines to break in a horrible 
manner, so I'd prefer not to go back to that version...

>  I'm not sure if that matters to any other user-space app. (or if
> ideally one is supposed to be able to control brightness in the console
> without having to load i915), but it's fine for controlling brightness
> in Xorg.

If you use modesetting then you shouldn't need to launch X to get 
working brightness control. The problem with the old-style world is that 
you won't get interrupts until X comes up.

-- 
Matthew Garrett | mjg59@srcf.ucam.org
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