tbstream_ring_available
if (!tbstream_ring_available(&sdev->tx_ring))
while (!tbstream_ring_available(&sdev->rx_ring)) {
tbstream_ring_available(&sdev->rx_ring) ||
while (!tbstream_ring_available(&sdev->tx_ring)) {
tbstream_ring_available(&sdev->tx_ring) ||
if (tbstream_ring_available(&sdev->tx_ring))
if (tbstream_ring_available(&sdev->rx_ring))