In article <20060430134932.2088F2DA27@cvs.netbsd.org>
kiyohara@NetBSD.org wrote:

> Log Message:
> Remove sync-ope for descritor of DMA, because its descriptor set
> BUS_DMA_COHERENT flag.

BUS_DMA_COHERENT is just a hint (i.e. not provided on all architectures)
and sync ops would handle other stuff than cache sync (xfer data from/to
bounce buffer etc.), so you can't remove sync ops even if BUS_DMA_COHERENT
is specified.
(MD sync ops may return without cache sync if COHERENT flag is set anyway)
---
Izumi Tsutsui