SIZEOF_SIG
desc_size = mm_desc_size(pdev, DESC_TYPE_L2RX_PACKET) + SIZEOF_SIG;
pkt = (lm_packet_t *) (mem_virt + SIZEOF_SIG);
descSize = sizeof(um_rxpacket_t) + SIZEOF_SIG;
pMem = (caddr_t)pRxPkt - SIZEOF_SIG;
pRxPkt = (um_rxpacket_t *)(pTmp + SIZEOF_SIG);