Comment 96 for bug 12637

Additional comments:

- Another source of LCD dim: alternating between virtual terminals (Ctrl+Alt+F2; Alt+F3; Alt+F7...)
- Manual rebooting (typing 'sudo reboot', at a terminal) seems to not dim LCD

Ok, a few more tests as: https://wiki.ubuntu.com/DebuggingACPI

** Methodology: Every parameter was tested after the kernel was booted with 'acpi=off', inclusive **

Results:

1. 'acpi=off': no LCD dim at boot (OK!!!) and function keys for brightness started to work for the first time ever!!
   (*) Complain about 'pnpbios=off' necessary as a kernel paremeter;
2. 'acpi=ht': no LCD dim at boot (OK!!!) and function keys for brightness still working!!
   (*) Complain about 'pnpbios=off' necessary as a kernel paremeter;
3. 'pci=noacpi': LCD dim back at initng time; function keys for brightness don't work anymore (NOT OK); LCD dim at shutdown time again;
4. 'acpi=noirq': LCD dim back at initng time; function keys for brightness don't work too (NOT OK); LCD dim at shutdown time again;
5. 'pnpacpi=off': LCD dim back at initng time; function keys for brightness don't work (NOT OK); LCD dim at shutdown time again;
   (*) Complain about 'pnpbios=off' necessary as a kernel paremeter;
6. 'noapic': LCD dim back at initng time; function keys for brightness don't work (NOT OK); LCD dim at shutdown time again;
7. 'nolapic': boot hanged at 'Starting up ...\nLoading, please wait...'; initng waving the progress bar endlessly

Last comments:
- Font rendering at text virtual consoles degradated a little bit while changing ACPI parameters;
- Fan went to full speed without ACPI;
- System could not boot properly right after 'nolapic' test; hard reboot necessary to bring it back to work.

It seems that the problem lies within ACPI. I'll investigate more from there. More attachments below in the aim to help debugging, as indicated in the website above.