Hi,
You haven't given an example of where this might actually happen.
The driver is where the DMA mappings almost always occur because
that is the layer that knows the bus technology and therefore
the correct DMA interfaces to call.
What kind of driver do you have and what is this upper layer
doing the mappings for you but not giving you a pointer to
the kernel buffer as well?
Here I am dealing with a infiniband (see www.openfabrics.org) network
device driver. The layer above the
driver is the standard infiniband core interface. Now I have a situation
where I need to peek into the packets
and do some modifications(some hacking). So I just want know whether I
can access the original data region
using the bus address generated by the dma_map_single.
FYI, architecture I am working on is x86_64.
-Mahesh
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