Network device driver Question

[John Newlin]

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@xxxxxxxxx


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