[lwip-devel] Your opinion - zero copy transmit - Freescale Kinetis

[jhinkle]

I'm developing my own device driver for Freescales K60 - Kinetis ARM cpu - on
a Crossworks platform.

I've reviewed the ones that Freescale provide but they all copy data from
the pbuf chain into predefined transmit buffers.  Not a Zero-Copy
implementation.

The ENET on this micro requires a memory alignment of 8 bytes when using the
internal dma and placing the pbuf data pointers directly into the ENET's
Transmit Buffer.

To implement this, I would need to make changes to the pbuf allocate
routines to make the 8 byte alignment only associated with pbufs and not
non-pbuf mem_alloc().

The trade of to the code modification is zero-copy data on transmit.

I suspect this is a good trade-off (custom pbuf alloc) for the time saved
doing mem_copy for every transmission.

I would appreciate any comments on this topic.

Thanks




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