Am Samstag, 30. Oktober 2004 16:39 schrieb Axel Waggershauser:
> I have no sufficient knowledge of the whole scatter-gather method but I
> thought version 2 (avoiding copy_to/from_user with sg) would exactly be
> the way to go. As far as I understand it, any memory block in user-space
> may be at most fragmented into single pages so where would be that
> problem with "correct packetization" compared to the suggestion from
> Duncan of scattering single pages in kernel-space? Is the problem that
> the user-space memory block would have to be page aligned?
In essence yes. A packet must not cross a page boundary. To guarantee
this, you would use a mmapped buffer, which in kernel would be allocated
with the dma_* methods and exported.
How you could use libusb on top of that is unclear to me, considering
error handling. Another issue is limiting the amount of memory pinned thus.
Regards
Oliver
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