memory mapping (was Re: can't address PC bus)

[Rob Peglar]

In article <11845 at hub.ucsb.edu> 6600joef at ucsbuxa.ucsb.edu (Joe Foster) writes:
>In comp.unix.xenix.sco <chris at neabbs.UUCP> writes:
>
>>Who knows if it's possible to adress the PC-bus, when your
>>computer is running under SCO Unix V/386 version 3.2?
>
>Only the UNIX kernel may directly access I/O ports and physical memory (in
>case those cards are memory-mapped). Your friend will have to write drivers
>for each interface card. There are plenty of books and things on this
>subject, but writing device drivers is something like black magic. If these

Not entirely true.  Check out the vas() calls available in 3.2.  These
calls will allow user processes to access (physical) memory.  Once the
proper vas() calls have been executed (typically in a trivial device driver's
init() portion) any user process can see the memory.  Perfect for memory-
mapped add-on cards, e.g. video.

BTW, drivers aren't that hard.  Just read the book(s) on them.  No magic,
just a different mind-set.

Rob
-- 
Rob Peglar               Network Systems Corporation
Internetwork Group       7600 Boone Avenue North
robp at anubis.network.com  Minneapolis MN 55428   (612)424-4888 x1028