Real Time UNIX (was: Re: How do you tell a wizard?)

[News system owner ID]

jfh at rpp386.cactus.org (John F. Haugh II) writes:
< It is very worth pointing out that Plexus used UNIX kernels on
< their serial I/O processor cards.  I don't know if anyone from
< Plexus [ is there still a Plexus??? ] is listening and has any
< info on that implementation.

Oooooo Ick!  That must have been a mistake.

Since I'm fairly new (I started by playing with 4.1 BSD), I'll ask a
few of the old(er)-timers out there: has there ever been a UNIX serial
driver that worked right?

What I (personally) want to see is something that will do some version
of the normal cooked vs. not processing (pref. designed to be
configurable, like Sys V's, rather than hacked, like Berkeley's), will
actually _do_ hardware flow control, correct modem control, sync, and
async if the hardware can (without reconfiguring the kernal to do so),
and is eficient enough to handle sustained input at 38.4Kbps (if the
system has a DMA serial board).  It should also handle non-blocking
I/O, and deliver SIGIOs, if asked.  And the user should be able to
tell it to allocate bigger, smaller, default, etc. amounts of input
buffer storage.

Yes, the 38.4Kbps and flow control, etc. are highly dependant on the
hardware, but in the "newer" UNIXen, on machines with perfectly
capable hardware, getting this all to work for a user-level process is
like pulling teeth (or just plain imposible).

Show me all this, and I will show you a happy serial I/O hack indeed.
The current ones are set up for the special case of talking to an
ordinary terminal.  Unfortunately, there are much more things that can
be done with a serial line...

		-- Paul Placeway <PPlaceway at bbn.com>