|Subject:||Re: [lwip-devel] again... Zero Copy Ethernet interface|
|Date:||Tue, 23 Dec 2008 17:36:12 +0100|
As I was advised on this list last year, zero copy with DMA is possible and not difficult (for incoming packets) by allocating pbufs and pointing the DMA controller at the pbuf payload (you may have to play with alignment of this pointer depending on the architecture). When a packet arrives, allocate a new pbuf, set the DMA controller to this new packet and return the pbuf that the DMA controller just filed to the caller of low_level_input.
As also mentioned in the past, outgoing zero copy is more difficult because lwIP wants to free the pbuf after the call to low_level_input and this could happen before the DMA transfer has occurred. Maybe I have this wrong but I recall some complication in regards to sending data.
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