tag	line	file	source code
UART_LSR_DR	220	kernel/chr_drv/serial.c	if (status & UART_LSR_DR) {
UART_LSR_DR	260	kernel/chr_drv/serial.c	UART_LSR_DR);
UART_LSR_DR	387	kernel/chr_drv/serial.c	} while (inb(UART_LSR + port) & UART_LSR_DR);