zero copy network driver

From: Ask (ask8y_at_yahoo.com)
Date: 08/26/04 

Date: 26 Aug 2004 07:39:42 -0700

Implementation of transmit function.
 hard_start_xmit(struct sk_buff *skb, struct net_device *dev).
If I do zro copy, iahve to make sure the data in the buffer has been
transmitted by the hardware not just tell the hardware start to
transmit.

If the hardware runnning in poll mode, I can poll the buffer
descriptor to see if the transmit has been done before the retunn. And
this is not very good, in the sanse that even the hW does not pushed
out the data, the driver might have idle buffer descriptor available
to accept data. But at leat I am sure the data has been pushed out by
HW before the function returns.

However if in in interrupt mode (most likely it'b be in), how could I
handle this? Before next interrrupt happens I could not if the data
has been pushed out by the HW. If the function just returns after tell
HW to start transmit, it might happens that the calling function
release the buffer even before the HW transmits it.

Thanks for your help.

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