In your letter dated Fri, 14 Aug 1998 09:53:50 -0700 (PDT), you wrote:
>You should be using bus_dmamem_alloc() and bus_dmamem_map() for any memory
>that the chip will be doing DMA to/from (see dev/sbus/if_le.c).  

right, although it will be much more complicated for the midway
because the driver DMAs directly to/from the data areas of an mbuf.
[i.e. it doesn't do any data copying at the driver layer...]  
so you will have to map and unmap each mbuf you get as you receive
them.  i don't think bus_dmamem_alloc() will be useful since we
always deal with mbufs whose data areas are already allocated?


>Lookin in `midwayreg.h', It would be a good idea to remove the
>compatibility bus.h stuff since there's the line:
>#define vtophys(x) ((u_int32_t)(x))     /* sun4c dvma */
>This implies that you will have DVMA issues.

you pretty much have to have DVMA issues on a sun4c.  at the time
i wrote the driver the rest of the framework wasn't ready.   it would
be an interesting project to make the sbus version of the card
go again.   unfortunately i no longer have access to ATM or any 
sun newer than a sparc2.


chuck