I've just managed to adapt the (2D) accelerated SIS671 driver* to use the new pciaccess mechanism. The driver seems to work fine but I haven't test any movie on it. And the driver will crash if using the default XAA. So you'll need the new acceleration mode, EXA. And you'll also need to use "MigrationHeuristic" "greedy" in the device option.
Code:
Option "AccelMethod" "exa"
Option "MigrationHeuristic" "greedy"
If there's anyone want it I can upload it later, if not, then feel free to close the thread.
* From:
http://www.linuxconsulting.ro/xorg-drivers/