generic 'dev' loopback driver ?

is there anything around which implements a generic
'dev' loopback driver, i.e. something that appears
as a /dev/foo entry on one side, and transparently
passes requests (open, ioctl, read/write) suitably encoded to a
file descriptor ?

I am basically looking at the skeleton of
something like pty-ttyp or tun-/dev/tun and so on...

	cheers
	luigi