The penguins have developed a "stable" userspace driver
API to allow "most" of a driver to be in userland.

http://liquidat.wordpress.com/2007/07/21/linux-kernel-2623-to-have-stable-userspace-driver-api/

No DMA (yet?).  Not for drivers requiring the highest
possible performance.

It doesn't solve the problems of binary-only drivers.
(security, fixing bugs, CPU arch, ...)

But if they did a reasonable job (and yes that's a significant if),
it might be useful for many drivers.  Perhaps a way to share
drivers between Linux, the BSDs, OS-X, OpenSolaris, ...

Thoughts?