DVMA device driver works with SunOS 4.0.3 doesn't with 4.1

[Marcus Gates]

We have a device in vme32d32 space on a sun 4/260 which uses DVMA. The
driver works under 4.0.3 SunOS but when we switched to SunOS 4.1 (and
4.1.1) the device no longer works prpoperly.  One difference I'm aware of
is that the 32-bit VMEbus address space allocation was changed between
4.0.3 and 4.1.  The driver uses mbsetup() to double-map buffers into
kernel DVMA space and also into usr address space, 4.1 Release notes
mention a new routine mb_mapalloc() for allocating DVMA space but says the
old mbsetup(), mbrelse() should work.

The symptoms make it look like there might be a conflict between Sunview
and this driver (one is overwriting data needed by the other?).
Occasionally the driver will work for an extended period of time but in
that case all other processes appear to be given no time so nothing else
(including logins) runs and the system is hung.

Any clues would be greatly appreciated as we would very much like to be
able to run this device on newer suns which will undoubtedly come with
4.1.1 or something even newer installed.