Dim on battery doesn't work as expected [HP NX 6120]

[Onkar Shinde]

Binary package hint: gnome-power-manager

Ubuntu version: 6.06.1

Expected:
Dim on battery should decrease the brighness of screen when on battery power.

Actual:
Two separate states/levels of brightness are maintained, one for AC power, one for battery power.
Removing AC power just switches screen brightness to corresponding (battery power) level.

[Matthew Garrett (mjg59)]

There is no kernel driver to set the brightness on HP laptops.

[Onkar Shinde (onkarshinde)]

I don't understand. I can increase/decrease brightness by using Fn + F9 / F10 keys. And this works out of box.

Just in case needed, laptop testing report is at https://wiki.ubuntu.com/LaptopTestingTeam/HPNX6120

[Matthew Garrett (mjg59)]

That's done by the hardware. Linux has no way to control the brightness.

[Onkar Shinde (onkarshinde)]

Please explain it to me. I don't have very vast knowledge of hardware.

If brightness control is done by hardware then who maintains the two levels of brightness, one for AC power and one for battery power?

[Matthew Garrett (mjg59)]

The hardware. There are two values stored in the non-volatile RAM.

[tuharsky (tuharsky)]

With Ubuntu 7.04 Feisty, it works seamlessly on HP Compaq nx6310 and it DOSEN'T work on the HP Compaq nx9105.

Reopening.

[tuharsky (tuharsky)]

With 7.10 Gutsy, still DOSEN'T work on HP Compaq nx9105.

[MillenniumBug (millenniumbug)]

This bug report is several years old and concerns obsolete versions of Ubuntu. It has now been marked 'invalid'.

If the bug still appears in Ubuntu 10.10, feel free to open a new report.