PCM_MAX_PACKET_SIZE
PCM_N_PACKETS_PER_URB * PCM_MAX_PACKET_SIZE;
rt->out_urbs[i].buffer = kcalloc(PCM_MAX_PACKET_SIZE,
rt->in_urbs[i].buffer = kcalloc(PCM_MAX_PACKET_SIZE,
.period_bytes_min = PCM_N_PACKETS_PER_URB * (PCM_MAX_PACKET_SIZE - 4),