tn40_rxf_desc
nr = priv->rxf_fifo0.m.memsz / sizeof(struct tn40_rxf_desc);
struct tn40_rxf_desc *rxfd;
rxfd = (struct tn40_rxf_desc *)(f->m.va + f->m.wptr);
f->m.wptr += sizeof(struct tn40_rxf_desc);