[lwip-devel] [bug #49914] lwip_sendmsg uses PBUF_REF pbufs

[Dirk Ziegelmeier]

Follow-up Comment #11, bug #49914 (project lwip):

Even DMA-enabled netifs have more problems. I wrote a driver for the Synopsys
Designware MAC (in Linux its called "stmmac"). It is capable of scatter-gather
DMA, but has alignment requirements for the buffer (I guess resulting from
burst-access boundaries). So even for this MAC, I was unable to use zero-copy
TX because the RAM PBUFs did not satisfy the alignment requirements.
To make this work, there most flexible way would be to allocate TX PBUFs via a
callback from the application...
Zero-copy TX can be quite challenging.

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