[mc1322x] Extra two bytes on xmit

[Mariano Alvira]

On Wed, Nov 18, 2009 at 06:41:58PM -0500, Jon Smirl wrote:
> When I change len + 4 to len + 2, the RS (solicitation) packets are
> correct and the router responds with RA.
> Why is this +4?
> 
> 	/* set dma tx pointer to the payload */
> 	/* and set the tx len */
> 	reg32(MACA_TXLEN) = (uint32_t)(len+2);
> 	reg32(MACA_DMATX) = (uint32_t)tx_buf;
> 	reg32(MACA_DMARX) = (uint32_t)rx_buf;
> 	reg32(MACA_TMREN) = 0;
> 
> 
> We aren't hearing the RAs when they come back.

This has it's source in the freescale code:

Weather Station Controller/SMAC/Source/RadioMngmntWrapper.h:
maca_txlen = (uint32_t)((maMessage_Queu[current_msg]->u8BufSize)+4); \

Weather Station Controller/SMAC/Drivers/Interface/ghdr/maca.h:#define
maca_txlen_max_rxlen          (127<<16)

And in rftest-tx.c I couldn't account for the + 4 either:

   #define PAYLOAD_LEN 16 /* not including the extra 4 bytes for
   len+fcs+something\ else */
   /* maca dmatx needs extra 4 bytes for checksum */
   /* needs + 4 bytes for len(1 byte) + fcs(2 bytes) + somethingelse */

Is it possible that in Contiki len includes something that I/Freescale
don't count as the payload? Like the FCS? That could explain why
changing it to 2 works.

-Mar.