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

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

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

View attachment "intel_panel_..._backlight" of type "text/plain" (4472 bytes)