BTH_ACK_MASK
return 0 != (cpu_to_be32(BTH_ACK_MASK) & bth->apsn);
bth->apsn |= cpu_to_be32(BTH_ACK_MASK);
bth->apsn &= ~cpu_to_be32(BTH_ACK_MASK);
psn |= BTH_ACK_MASK;