amd64 bus_space_*_8() functions

[Dennis Ferguson <dennis.c.ferguson%gmail.com@localhost>]

I'm porting a driver for a PCI board into NetBSD-current.  The
device in question has 64-bit registers, so the driver needs
bus_space_read_8() and bus_space_write_8().  While most of the
other 64-bit architectures seem to have the _8() versions of these
functions implemented it looks to me like the amd64 port does not.

Is there a reason why the amd64 port doesn't have them, or
is this just because of lack of any previous need for them?
And if the latter is the case and the functions just need to
be written, what should the assembler stubs do if they are asked
to do an 8-byte operation to I/O space?

Dennis Ferguson