Re: RFC bus_dma_tag_parent
:This is useful if the bus DMA engine supports scatter/gather itself.
:This can be done IIRC on the Alpha, maybe on other architectures too.
:I don't mind if we have a UNKNOWN value, e.g. 0. This is not a problem
:here, but for many drivers we know this in advantage and it might be
:used to allocate the segment maps in the parent tag.
:
:Joerg
Yes, that makes sense. I think the best approach to the allocation issue
is to solve the real problem, and that is to allow a dma tag to be
flagged as being just a topological specification, and panicing if
someone actually tries to initiate DMA using the topological
specification. I would rather not delay the allocation of the
scatter/gather array to hack around the lack of knowledge.
-Matt
Matthew Dillon
<dillon@backplane.com>
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