Jason R Thorpe <thorpej@wasabisystems.com> said;

>> XXX: diffs between current pmax and alpha scc.c are almost as large
>>      as the files themselves.  Should clean this up...
> Should drop scc.c completely, actually.

Sure.   struct pdma is unnecessary to have and bogus indeed.
If "paired Zilog SCC" driver is made for DECstation 5000 and
DEC3000, following points are worth considering;

- channel renumber
DEC wanted the paired SCC to emulate "DEC standard assignment"
of 4 channel DZ serial;

0: keyboard, 1: mouse, 2: comm/modem, 3: printer/console

NetBSD treats as if Zilog SCC has two independent channels to handle.
Unfortunately the Zilog does not work in such way. ULTRIX/OSF1
treats the pair as if it was 4 channel DZ.  Single chip MAXINE case has
to be taken into consideration too.

- IOASIC DMA for serial TX/RX
Which expense of wasteful buffer space, IOASIC can play DMA work
for them.

Tohru Nishimura