@kaxing, Win8 doesn't use ACPI to control backlight but leaves control to gfx driver instead. If system tells BIOS that it has win8 capability, BIOS will disable ACPI backlight interface. Linux kernel starts to support Win8 capability after 3.7. That's why ACPI backlight control works on early kernel version.
For win8 backlight issue, please refer to following article. http://www.linuxjournal.com/content/july-2013-linux-kernel-news -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1354313 Title: [Dell Inspiron 5721] Brightness control does not work with 12.04.5(with kernel 3.13) To manage notifications about this bug go to: https://bugs.launchpad.net/hwe-next/+bug/1354313/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
