Re: [lwip-devel] again... Zero Copy Ethernet interface

[Jakob Stoklund Olesen]

bill wrote:
> Thanks Jakob, this is helpful.  Is 'can_direct_dma' just a check for
> 'pb->next == NULL' or are you supporting DMAing the pbuf chains making up
> the whole packet?

That depends on the device.

I have one device that can DMA two segments if the first one is less
than 100 bytes and both are 4-byte aligned.

Another can DMA up to 8 segments if they are all 2-byte aligned.

If there are too many pbufs in the chain or some payload is not properly
aligned, I just copy the entire packet to continuous memory.

/stoklund