[This RFE is duplicated in the two categories concerned:
doc/devicedriver & manpage/section9f]
The ddi_umem_iosetup(9F) function (See RFE 4159321) is mentioned in
the man pages only in the ddi_umem_lock(9F) page, and not all in the
document "Writing Device Drivers". In short, it is really hidden in
documentation. This is apparently the only function that allows the
creation of I/O+mmaped memory (it is used in common/io/rsm/rsm.c), and
I had to bother several busy kernel experts before knowing it
existed. I think someone outside Sun facing my problem would have
never known about it and given up.