I used to run Dream Studio Unity (ivy bridge version) on sandy bridge on Thinkpad Edge E530 (B960 proc.), which worked OK, but after it updated itself to kernel 3.8 no more enables to set display brightness correctly - only maybe 0.5 step (displayed on-screen) or zero (really) from minimum (not great for e.g. photography...), while hardware continues to work correctly with 3.5-kernel-32-bit ArtistX 1.4. I am now trying success with yet newer 64-bit Ubuntu Studio from April 2013, but precisely the same bug haunts this version also (3.8.0-19-lowlatency #13-Ubuntu SMP PREEMPT Thu Apr 18 09:41:59 UTC 2013 x86_64 x86_64 x86_64 GNU/Linux ). What should I do best now? If I installed manually some additional sw to basic Ubuntu 12.04.2LTS or 12.10 (or installed originally 3.2-kernel version Dream Studio Unity), which one will stay with 3.5 or lower kernel without intervention for at least 5-6 months? Is there probability the bug will present itself even so?


See comment #2 in this bug report for a partial fix (partial because the indicator is still malfunctioning afterwards). In short:

Add acpi_backlight=vendor in file /etc/default/grub (open the file from a terminal using this command sudo gedit /etc/default/grub) to the end of this line GRUB_CMDLINE_LINUX_DEFAULT="quiet splash. So it should look like this:

GRUB_CMDLINE_LINUX_DEFAULT="quiet splash acpi_backlight=vendor"

Then run sudo update-grub and restart.

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