length_to_duration
int min_duration = length_to_duration(q, ETH_ZLEN);
if (new->cycle_time < new->num_entries * length_to_duration(q, ETH_ZLEN)) {
packet_transmit_time = length_to_duration(q, qdisc_pkt_len(skb));
packet_transmit_time = length_to_duration(q, len);
guard = ktime_add_ns(taprio_get_time(q), length_to_duration(q, len));