Device Drivers in SCO Xenix

[Don Acton]

I am trying to write a device driver for SCO's Xenix SYSTEM V release 2
version 2.0.6 running on an IBM PC/AT and am having a few difficulties.
The device is being treated like a tape drive in that it has both block
and raw access modes. One problem area concerns the notion of a paddr_t
and and a kernel logical address. I can't find anything in the manuals
that explain just what these "things" are and how they are related to
either the "near" or "far" pointers in normal program use. What sort of
gymnastics must one do with these objects before they are usable?  My
second problem concerns physio. When I call physio, as specified in the
manual, it returns with a u.u_error code of 14 (bad address) and never
calls my strategy routine. (The call to read or write in the user
program is correct as things are fine if I have the program open a
file/device other than the one I am writing the driver for.) If anyone
has any insight into these problems their help would be greatly
appreciated. 

  Donald Acton

  please respond by email

  {utzoo, seismo, uw-beaver}!ubc-vision!mprvaxa!acton
      or
  acton at mprvaxa.uucp