I have noticed that direct rendering is not enabled when the
X window system is started for the first time after booting.
libGL error: open DRM failed (Operation not permitted)
Exiting and restarting solves the problem, as does modprobing
the Mach64 module before starting the X window system. Is this
a udev latency issue, or does the cause lie elsewhere?
Adding the rule 'KERNEL="card0", NAME="dummy"' to the top of
'udev.rules' also solves the problem.