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

[Peter Graf]

Hi Nicolas, Dan,

>I have written a driver for the RTL8019AS, it works ok but still has some 
>strange glitches. Maybe we can work together, and then release our work ?
>
>Nicolas
>
>Quoting Dan Lewis <address@hidden>:
>
> > 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)?

Seems like we're three, I'm also tinkering with a NE2000 driver.
My implementation does *not* rely on word-alignment of the pbuf chains,
especially not that the *end* of each sub-buffer fills a 16 bit word!
(Is there any spec about this?)
Moreover it's better to be on the save side for sub-buffer usage changes
in the future. I have a big-endian CPU so I must re-arrange the data
anyway before I do the actual 16-bit access to the ethernet chip.
Way too early to release my code, it's a mess right now. Just my
experience with NE2000 chips: Check hardware timings carefully.
Insert waits (e.g. by empty bus access) where in doubt.

All the best
Peter


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