Laptop LCD brightness settings remain in BIOS

[mannheim]

Binary package hint: acpi-support

Steps to reproduce:

1. Buy a Dell XPS M1330 laptop and install Ubuntu 8.10.
2. Plug it into AC, turn on machine and press F2 to enter BIOS.
3. In BIOS make sure AC brightness is configured to max value (8).
4. Boot into Ubuntu, and use Fn-DownArrow to decrease brightness.
5. Restart and enter the BIOS again. Check the value for AC brightness.

Expected results: AC brightness is back at 8.
Actual results: AC brightness is set at a lower level in BIOS.

Although the actual behavior is maybe the desired behavior in some uses, it causes problems for dual-boot systems. Windows Vista appears to handle brightness differently: on this machine, the value set in the BIOS is interpreted as a maximum in Vista, and the brightness hot-keys control the brightness within that smaller range. (So if AC brightness is set to 3 in the BIOS, then the hot-keys in Vista will cause the actual brightness to vary only in the range 0-3.)

[Steve Langasek (vorlon)]

Thank you for taking the time to report this issue and help to improve Ubuntu.

This hotkey is not handled by acpi-support; it must be handled by either gnome-power-manager or the kernel. Reassigning to g-p-m.

[Nicolò Chieffo (yelo3)]

libsmbios is the library to change dell brightness, reassinging. Anyway it's the harwdare keys which does the thing (I think)

[Cyril Lavier (davromaniak)]

Hi.

I can confirm this bug.

I have the same problem on my Dell XPS M1330, and it's not really annoying, but I think it would be better if it fixed.

So I change the Status to "Confirmed".

Thanks.