[lwip-users] Re: [lwip] Word mode transfers in an ethernet driver

[Kieran Mansley]

On Thu, 28 Nov 2002, Dan Lewis wrote:

> I'm porting lwIP to a PC104 board that uses the RealTek RTL8019AS
> Ethernet controller. The board has the RealTek chip configured for
> word-mode transfers. The sample driver transfers data to/from the
> Ethernet controller by walking through the pbuf chain and then (within
> each pbuf) transfers the pbuf contents to the Ethernet controller one
> byte at a time. I'd like to transfer the data one 16-bit word at a time.
> Does anyone know whether or not pbufs always contain an even number of
> bytes (except possibly the last pbuf in the chain)?

If I remember correctly, the pbuf code uses the MEM_ALIGN_SIZE macro to
round the size of all pbufs when allocated to be a multiple of
MEM_ALIGNMENT.  This is by default 1, but maybe you could change it to 2
and see if that helps, and if it impacts anything else.

Kieran

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