mmap() under SunOS 4.0

[Andrew Arensburger]

Sun used to have a nice, well-behaved routine called 'mmap()', which took
a block of memory, and mapped it to a device such as -- in my case -- a
VMEbus.  Sadly, they changed it with SunOS 4.0.  Now, instead of returning
an (integer) error code, it returns a pointer (or -1 in case of error.
Aaarggghh!). It is unclear what the return value has to do with the
pointer one has passed in, or indeed what the routine does, now.

I need to map certain addresses on /dev/vme16 and /dev/vme24 to user
memory. Does anyone have any experience with 'mmap()' under 4.0?  How do I
go about using it? (The manual page is particularly unclear).