Re: Linux DMA address

On Tue, Jul 3, 2012 at 6:37 AM, Klaus Wacker [off-list ref] wrote:

1.) Is it possible/allowed to call ib_dma_map_single() on Linux, same
buffer address, size and dma_data direction, for two different ib devices?

Yes, this should be no problem.

2.) If this is possible, will the returned dma_addresses be the same? Any
dependencies on the adapter model?

There is no guarantee about what the addresses will be.  For example
if the adapters are behind IOMMUs (eg Intel VT-d) then it is quite likely
the dma addresses will be different for each ib device.

As Or has said, ib_dma_xxx functions are pretty thin wrappers around
the normal dma api -- they're just there to handle ib devices like qib/ipath
that emulate dma in software.  So if you understand the dma api then
the same answer should apply to the ib_dma_ functions.

 - R.
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