Created attachment 26159 [details]
Since KMS, I was having trouble with DVI2 being falsely detected as connected, I though this caused xbacklight to stop working, however, since this first bug has been resolved, xbacklight is still not working.
jerome@MobileCPU ~ % xbacklight
No outputs have backlight property
Attaching Xorg.0.log just in case.
thanks for filing this. But it looks like a known issue.
*** This bug has been marked as a duplicate of bug 20963 ***