[Jaunty] SRU: Fix video backlight regression on Acer laptop

Tim Gardner tim.gardner at canonical.com
Tue Sep 1 19:13:22 UTC 2009

Stefan Bader wrote:
> SRU justification:
> Impact: After I carelessly pulled in some updates to the ACPI video 
> code, we were faced with some regressions. One was (at least) a certain 
> Acer laptop model that suddenly had no backlight control.
> Fix: As the ACPI BIOS is broken on a way that only the *wrong* graphics 
> definition will be accepted by acpi-video as the right definition lacks 
> an attribute to be considered, the fix is to have less strict 
> requirements to that check, so the definition for the right graphics 
> device gets accepted (a patch doing that unconditionally, has been 
> submitted upstream and has been acked, but might not make it until 
> 2.6.32). For the stable tree I created more code which makes sure the 
> less strict tests only take effect on that laptop or when the user 
> really wants to.
> Testcase: Booting on another laptop will not activate the code (which 
> prints a "Using less strict video detection..." message) but will do 
> with "acpi_video_strict_detect=0". In both cases nothing bad happened. 
> The affected laptop boots and selects the new check which gives back the 
> backlight control.


Tim Gardner tim.gardner at canonical.com

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