I see the CONFIG_DRM_RADEON_UMS kernel option was disabled in Utopic but not Trusty. However, you did not see the bug until after 3.16.0-17, but CONFIG_DRM_RADEON_UMS was also not set in 3.16.0-17.
I think our best bet is to bisect between v3.16.3 and v3.16.4. It will require testing about 8 - 10 kernels. I'll build the first test kernel and post a link to it shortly. -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1407505 Title: No UMS support in radeon module To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1407505/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
