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.

-- 
LCD Brightness on Laptop Always Set Very Low at Boot
https://bugs.launchpad.net/bugs/12637
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