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SubjectNetwork device driver Question
I'm working on a driver for a new device.  This NIC is on-chip, and 
memory mapped.
It can DMA to/from any memory location.

I am trying to optimize the driver such that it there is no need to copy
to/from sk_buff
in the send_packet and on packet receive.

The problem I have is with a CPU that has a writeback cache. When the
send_packet
is called, the data in the sk_buff may be cached. In the driver I can
allocate a page as
uncached and copy to that page, however I am trying to avoid unneeded
copies.

For receive there is a similar problem. When I allocate the sk_buff I
need to invalidate
the caches. That way after a new packet arrives a read from that memory
location will
not hit in the cache and return incorrect data.

Is there some sanctioned way that will work on any architecture to cause
a writeback
of the dcached based on a range of virtual addresses, and similiarly
cause an invalidate?

Thanks,

-John Newlin
jnewlin@rawbw.com


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