I too can confirm this. I've the same machine (XPS l702x aka XPS 17), display (hd 3D), and graphics card (GT 555m). Same results on each of the above suggested tests. All indications (OSD, /proc values, g-p-m output) are that the brightness is changing, but the actual screen does not change. (Haven't tried the reboot trick yet.)
-- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/762670 Title: Laptop brightness on Dell XPS not controllable -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
