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SubjectRe: DMA mapping
David S. Miller wrote:
> If it was a nice piece of hardware, perhaps a 64-bit handle would have
> been used so that you could stick the whole address in there on any
> given current architecture and then you wouldn't even need the
> silly bus_to_virt calls :-)))))

Hmm, remember ISA DMA ? ;-)

> I suppose you saw the recycling mechanism provided by the
> Microsoft NT driver interfaces and considered if such a
> scheme would benefit Linux as well?

Historical note: on ATM, we tried several things to deal with large
skbs (the IP over ATM default MTU is ~9 kB, and the worst-case
packet size is even 64 kB), while avoiding extra copying. This was one
such attempt. Well, perhaps unsurprisingly, it didn't work all that
well. The current wisdom is to allocate a pool of receive buffers that
are then memcpy'd to the real skbs :-(

- Werner

--
_________________________________________________________________________
/ Werner Almesberger, ICA, EPFL, CH werner.almesberger@ica.epfl.ch /
/_IN_N_032__Tel_+41_21_693_6621__Fax_+41_21_693_6610_____________________/

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