altera_jtaguart_tx_space
count = altera_jtaguart_tx_space(port, NULL);
while (!altera_jtaguart_tx_space(port, &status)) {
while (!altera_jtaguart_tx_space(port, NULL)) {
return altera_jtaguart_tx_space(port, NULL) ? TIOCSER_TEMT : 0;