In article <200603020740.17621.hselasky@c2i.net>
hselasky@c2i.net wrote:

> > Are you really expecting a physical address here, or is this some
> > convenient way to get at a single bus-dma opaque cookie, in an
> > already-existing dma_map, corresponding to the given kva?
> 
> Yes, it is just for convenience. The function should return the physical 
> address relative to the parenting PCI bus, which the hardware is on, which 
> should be programmed into the hardware.

Not all architectures use the physical address for DMA address
to be programmed into the hardware, so the name of *_vtophys()
is not appropriate.
(See Jason's bus_dma paper in src/share/doc/papers/bus_dma/)
---
Izumi Tsutsui