For my Thinkpad T430s, I can confirm that adding acpi_backlight=vendor as a grub boot option fixes the problem. I only have the Intel GPU enabled.
However, applying this boot options result in the OSD not correctly showing the current brightness state (s. attachment); it has always the same state. ** Attachment added: "Screenshot from 2013-09-27 01:44:43.png" https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1221795/+attachment/3843507/+files/Screenshot%20from%202013-09-27%2001%3A44%3A43.png -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1221795 Title: brightness stepping is incorrect (double what it should be) To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1221795/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
