Jason Thorpe <thorpej@nas.nasa.gov> replied:
> > 1.3/CHANGES refers to addition of generic ISA bounce buffer support.
> > Is it possible to add support for aha1542B (ISA) to 1.2.1 (if not
> > already there in non-generic form - isa/isa_machdep.h has some bounce
> > buffer defines)

> Not really, no.  The changes required to do bounce buffers correctly
> were quite extensive.

The changes required to do them "poorly" appear to still be available from
ftp://bseis.eis.cs.tu-bs.de/pub/hannken, though I don't know precisely which
of the many versions there will correspond to 1.2.1.  (These changes worked
perfectly well for their limited scope, and helped me limp along until the
beats-as-it-sweeps-as-it-cleans DMA architecture came along.)

That said, I think you'll find that the best way to add support for bounce
buffers to 1.2.1 is to upgrade to 1.3; it really is a whole lot better.  But
if you just can't, there's still an option.