[Jaunty] SRU: Fix video backlight regression on Acer laptop
stefan.bader at canonical.com
Thu Aug 27 22:09:50 UTC 2009
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.
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