something interesting to think about:

there exist PCI HBAs which provide regions which do, and regions which
do not do byte-swapping of the DMA byte stream between memory and PCI
devices.

not entirely sure how you could use that, but if you want to have any
possibility of using it you need support for it in the generic DMA
code.

also, your comment re: putting the device in big vs little endian mode
goes at least somewhat of the intent of the bus_ interfaces by
treating all devices on a given bus as if they have the endianness of
the bus...  granted, you want to do whatever you can to lower the host
processing setting up DMA data...  but i think you need some more
information in the interfaces...


cgd
-- 
Chris Demetriou - cgd@netbsd.org - http://www.netbsd.org/People/Pages/cgd.html
Disclaimer: Not speaking for NetBSD, just expressing my own opinion.