i compiled the whole dri (mesa + drm kernel driver ...).
now mach64 complains:

mach64: disagrees about version of symbol drm_open
mach64: Unknown symbol drm_open
mach64: disagrees about version of symbol drm_release
mach64: Unknown symbol drm_release

FATAL: Error inserting mach64 (/lib/modules/2.6.18-4-686/kernel/drivers/char/drm/mach64.ko): Unknown symbol in module, or unknown parameter (see dmesg)

dmesg tells the same ^^ (loglevel for console :>)
So far for the official part.
I compiled the drm as the mach64 drivers from the drm-sources (10 minutes ago).
it loads fine my intel_agp agpgart and drm.
just mach 64 does not like my kernel.
This is debian lenny (testing).
The card used is in a [bäh] Gericom [/bäh] laptop: Ati Rade 3D Pro LT
The hw-table points out to use the mach64-driver with this.
This is why only the mach64 was compiled by me.
all Kernel headers etc. are installed.
The one think i wonder, or what the Troubleshooting tells is a problem with 2.6.1 (far far beyond ^^)

dmesg | grep drm

(excluding the mach64-errors)
[drm] Initialized drm 1.0.1 20051102 (i wonder if this is really my compiled version)