... additional info to my previous comment: after enabling "Load Legacy Option Rom" in BIOS, backlight is working ok (also when I use f4/f5 keys).
Bios version A08, model XPS L322X -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1169376 Title: 8086:0166 [Dell XPS 13 L322X] backlight stopped working after update 3.8.0-18.28 To manage notifications about this bug go to: https://bugs.launchpad.net/dell-sputnik/+bug/1169376/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
