[net2-wg] Clarifications in CC2420 radio stack

[Joe Polastre]

Looking through the code, I think I'm missing something.  At a
previous net2 telecon, Phil told me that Jonathan's stack supports
selective link layer acks similar to Boomerang.  Basically only acks
are send when an ack is explicitly requested.  I've been searching
through the T2 CC2420 code and can't seem to find any acks taking
place.  I'm wondering what I'm missing...

Basically what I'm looking at is the ShortAddress is never actually
set in any of the code.  It is provided by CC2420SpiC, but never set. 
Why?

The PANID is set, but is set incorrectly I believe.  It casts a 16-bit
value to an 8-bit value, but IEEE 802.15.4 PANs are 16-bits.  Why the
cast?  Is TOS_AM_GROUP supposed to be 8 bits or 16 bits in T2?

CC2420ReceiveP 'uses' the SACK command, but nowhere in the file is
SACK actually called.  Is this a future addition?  How do you prevent
multiple packets in the FIFO causing the wrong packet to be ack'd (the
microcontroller slower than the radio problem)?

Commands for AutoAck, AddrDecode, and AutoCRC have been removed from
CC2420ControlP, so they can't even be turned on from an external
entity.  Why?

These questions come as part of looking at supporting SP on T2.

-Joe