linux-kernel - Re: i915/kms/backlight-combo mode problem

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Date:	Mon, 09 May 2011 10:58:19 +0200
From:	Takashi Iwai <tiwai@...e.de>
To:	Melchior FRANZ <melchior.franz@...il.com>
Cc:	linux-kernel@...r.kernel.org, "Joey Lee" <jlee@...ell.com>,
	chris@...is-wilson.co.uk, dri-devel@...ts.freedesktop.org
Subject: Re: i915/kms/backlight-combo mode problem

At Sat, 7 May 2011 22:22:40 +0200,
Melchior FRANZ wrote:
> 
> * Melchior FRANZ -- Friday 06 May 2011:
> > last patch prevents the backlight from being turned off, but it also
> > breaks the brightness adjustment keys at runtime with acpi_osi=Linux.
> 
> It has turned out that acpi key events seem to be handled correctly
> and even the state of /sys/class/backlight/acer-wmi/brightness is
> updated accordingly. The only problem is that this maintained
> brightness state isn't applied to the actual backlight. It remains
> at highest level. Google pointed me to this workaround for another
> Acer notebook:
> 
>   https://help.ubuntu.com/community/AspireTimeline/Fixes#Alternative%20fix%20for%2010.10
> 
> This uses the acpid to write the brightness value to the display
> using setpci. And this works on my notebook as well (Acer Travelmate
> 5735Z-452G32Mnss).

Then we miss something.  With the hack above, you are doing nothing
but writing LBPC register value externally from setpci.  It implies
that the write to LBPC basically works on your machine.


Takashi
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