The behavior is the lighting control works upon initial boot, but after leaving the computer on for multiple hours at some point the backlight ceases to respond and backlight controls are never regained until a shutdown or reboot of the system. I haven't tracked the exact pattern of actions that cause this. The on screen indicator shows the graphic of the dimming, but the actual behavior of reducing brightness does not function upon key press.
I noticed when the backlight was lost the following is added to dmesg, but I don't know how long before or after the loss that this message appeared: [ 9231.171766] usb 5-1: USB disconnect, device number 4 [11481.272220] perf interrupt took too long (2515 > 2500), lowering kernel.perf_event_max_sample_rate to 50000 [20859.513041] atkbd serio0: Unknown key pressed (translated set 2, code 0xab on isa0060/serio0). [20859.513049] atkbd serio0: Use 'setkeycodes e02b <keycode>' to make it known. [20859.533404] atkbd serio0: Unknown key released (translated set 2, code 0xab on isa0060/serio0). [20859.533413] atkbd serio0: Use 'setkeycodes e02b <keycode>' to make it known. [20859.832244] atkbd serio0: Unknown key pressed (translated set 2, code 0xab on isa0060/serio0). [20859.832253] atkbd serio0: Use 'setkeycodes e02b <keycode>' to make it known. Each press of the brightness key results in additional "atkbd serio0: Unknown key pressed (translated set 2, code 0xab on isa0060/serio0)...." values to be added to dmesg. May be related to resuming control after the screen goes blank after inactivity or other activity while idle? -- You received this bug notification because you are a member of Ubuntu-X, which is subscribed to xorg in Ubuntu. https://bugs.launchpad.net/bugs/1416186 Title: Periodically loss of backlight control To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/xorg/+bug/1416186/+subscriptions _______________________________________________ Mailing list: https://launchpad.net/~ubuntu-x-swat Post to : ubuntu-x-swat@lists.launchpad.net Unsubscribe : https://launchpad.net/~ubuntu-x-swat More help : https://help.launchpad.net/ListHelp
