Luigi Rizzo wrote:
>
> I probably missed some emails ?
> In any case i was only concerned about the additional copy
> done by m_devget when the controller can already DMA into
> an mbuf, and there are no alignment constraints.
I guess we are talking about a protocol other than IP? The
ethernet header is 14 bytes in length, which means that the
elements in the IP header are not longword aligned, unless
the card can DMA onto a 2 byte boundary, and does so, to
ensure that the IP header starts on a 16 byte boundary, and
therefore the contents are correctly aligned for direct
reference in a single bus cycle (or at all, on Alpha, where
unaligned access is not permitted).
-- Terry
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