Double brightness events

Joonas Saarinen jza at saunalahti.fi
Wed Nov 12 15:03:30 UTC 2014


Hi,

For years, Ubuntu has had this bug where a lot of laptops react to 
brightness adjustment in steps of 2 (or even 3). I believe this is not 
by design (correct me if wrong).

It seems that the brightness keypress is handled in multiple places. 
Possibly the OS does the adjustment, but does not consume the event and 
then BIOS does another adjustment.

Some machines can be fixed with this trick:
# echo N > /sys/module/video/parameters/brightness_switch_enabled

Are there plans to fix this bug? It's quite obvious one and immediately 
strikes you when you install and start using Ubuntu on a laptop.

Some affected laptops: Dell E4300, Asus F200CA, HP 6910p, Fujitsu E751...

Joonas Saarinen



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