I've upgraded from ati-driver-installer-8-5-x86.x86_64.run to ati-driver-installer-8-6-x86.x86_64.run and get
libGL error: open DRM failed (Operation not permitted)
libGL error: reverting to (slow) indirect rendering
when running as a user (it works just fine as root and the previous version worked just fine as anybody).
Did I miss adding users to some group, a permission somewhere or other or something?
EDIT: I Found the Answer (that I forgot about from a couple of years ago)
There are two choices to deal with this: first, allow any user access, edit /etc/X11/xorg.conf
Or, edit /etc/X11/xorg.conf