We later found that the backlight adjustment (using hotkeys) work normally after enabling the W540's discrete nVidia GPU (through installing nvidia-prime and nvidia-331 packages.) in Ubuntu 12.04.4.
@Acelan, does this suggest that " to disable the ACPI backlight interface on these systems" in the patch you mentioned would also work in Intel's case when applied? -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1270079 Title: [Lenovo T540p, W540] Backlight interfaces not fully working To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux-lts-raring/+bug/1270079/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs