On Mon, May 01, 2006 at 12:00:00PM -0700, Roland Dreier wrote:
> Arjan> do you really NEED the vaddr? (most of the time linux
> Arjan> drivers don't need it, while other OSes do) If you really
> Arjan> need it you should grab it at dma_map time ... (and
> Arjan> realize that it's not kernel addressable per se ;)
>
> Yes, they need some kind of vaddr.
>
> It's kind of a layering problem. The IB stack assumes that IB devices
> have a DMA engine that deals with bus addresses. But the ipath driver
> has to simulate this by using a memcpy on the CPU to move data to the
> PCI device.
>
> I really don't know what the right solution is. Maybe having some way
> to override the dma mapping operations so that the ipath driver can
> keep the info it needs?
Or stop doing the dma mapping in the IB upper level drivers. I told you
that we'll get broken hardware that doesn't want dma mapping in the upper
level driver, and pathscale created exactly that :)
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