UART_XMIT_SIZE    355 include/linux/serial_core.h 	(CIRC_CNT((circ)->head, (circ)->tail, UART_XMIT_SIZE))
UART_XMIT_SIZE    358 include/linux/serial_core.h 	(CIRC_SPACE((circ)->head, (circ)->tail, UART_XMIT_SIZE))