dvb_ringbuffer_pkt_next
idx = dvb_ringbuffer_pkt_next(&sl->rx_buffer, -1, &fraglen);
idx = dvb_ringbuffer_pkt_next(&sl->rx_buffer, idx,
idx = dvb_ringbuffer_pkt_next(&sl->rx_buffer, -1, &fraglen);
idx2 = dvb_ringbuffer_pkt_next(&sl->rx_buffer, idx, &fraglen);
extern ssize_t dvb_ringbuffer_pkt_next(struct dvb_ringbuffer *rbuf,