Repeatedly switching from AC to battery dims LCD to zero

[Andrew Oakley]

Binary package hint: gnome-power-manager

In Hardy on a laptop with all updates to date, unplugging the AC and then plugging it back in again, then repeating, eventually dims the LCD display brightness to zero.

To reproduce:

* Install Hardy on a laptop

* Use AC power

* Select System, Preferences, Power Management, On Battery Power, Reduce Backlight Brightness

* Using the laptop's built-in brightness controls (eg. Dell: FN-Up/Down), ensure the brightness is on full (100%)

* Remove the AC power

* Wait 2-3 seconds

* Plug the AC power back in

* Wait 2-3 seconds

* Repeat plugging and unplugging the power three or four times

What is expected to happen:

* The backlight should switch between two constant states; 100% for AC, dim for battery

What actually happens:

* The backlight gradually moves to dimmer and dimmer settings.

* Eventually, the backlight dims to lowest setting (0%) when on battery, and half setting (50%) on AC

This happens for me on a Dell Inspiron 1520 with Intel i965 X3100 graphics, but on the ubuntu-uk mailing list there is a report of this happening on an IBM / Lenovo Thinkpad too.

[David Hamm (davidthamm)]

I have this problem as well on my m1330, but what is more annoying is when adjusting the brightness, when i push the fn-up keys once the backlight goes to 50% and when pressed again, 100%. There is no gradual change. I can't put the back light at 25% or 75% only 0, 50% or 100%.

[Chris Smith (cs278)]

I can confirm this occurs on a IBM Thinkpad X22.