Asynchronous Driver

[Gary Craig]

Help! The project I am working on requires that an asynchronous device
driver be written.  The device is 68030-based, and allows DMA from/to the
host Sun by other computers on an external bus.  We have the (outside
world) <-> device interface squared away, but the device driver we
currently have (author now unavailable) only allows processes to make
synchronous I/O requests (i.e. the caller does not get control back until
the I/O is complete).

We are attempting to modify this driver to allow asynchronous requests, so
that (for example) the caller would be notified that the DMA is complete
by delivery of a SIGIO; he'd then do ioctl's to find out what happened.
The host is a Sun 4/380 running SunOS 4.0.3, vanilla.

Questions: Is there anything not made clear in Sun's "Writing Device
Drivers" manual relating to this task?  Anyone have any hints?
Specifically, will we encounter problems if the DMA destination address
(in the caller's context) is part of a memory segment shared with another
user process (via shmget, shmat)?  Anything else I should know?

Reply via email, please.  Many thanks in advance.

					Gary Craig
					gary at skat.usc.edu