DEF_FIFO_DEPTH_WORDS
geni_se_init(&se, DEF_FIFO_DEPTH_WORDS / 2, DEF_FIFO_DEPTH_WORDS - 2);
port->tx_fifo_depth = DEF_FIFO_DEPTH_WORDS;
port->rx_fifo_depth = DEF_FIFO_DEPTH_WORDS;
size_t avail = DEF_FIFO_DEPTH_WORDS - DEF_TX_WM;