linux-kernel - Re: back light conflict i915 vs dell-laptop

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Message-ID: <1290967527.4456.8.camel@lat1>
Date:	Sun, 28 Nov 2010 19:05:27 +0100
From:	Patrick Schaaf <bof@....de>
To:	Dan Carpenter <error27@...il.com>
Cc:	chris@...is-wilson.co.uk, mjg@...hat.com, rpurdie@...ys.net,
	kernelorg@....de, intel-gfx@...ts.freedesktop.org,
	linux-kernel@...r.kernel.org
Subject: Re: back light conflict i915 vs dell-laptop

On Thu, 2010-11-25 at 12:33 +0300, Dan Carpenter wrote:
> Patrick Schaaf has reported that the i915 driver is setting his
> backlight very dim when he starts GDM.
> 
> https://bugzilla.kernel.org/show_bug.cgi?id=23472
> 
> It should be the dell-laptop platform driver controlling his backlight.
> 
> Gnome tries to restore the backlight settings through the dell_laptop
> interface in sysfs but it fails.  (Because the platform hardware refuses
> to set the settings to what it thinks they already are).

As far as my instrumentation showed, gnome did try no such thing - there
were no setting calls through the backlight interface when I switch
between the GDM screen and text console.

I have now run with drm.debug=0x07 and noticed get/set backlight PWM
messages from intel_panel_get/set_backlight which became lower and lower
in value for each successive switching between GDM login screen and text
console, until reaching a low point and overflowing to 255255.

I append the extract of these kernel messages, as well as putting them
in the bugzilla entry linked above.

Hope this helps clarify the problems I'm seeing.

best regards
  Patrick

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