serial: export the key functions for an 8250 IRQ handler

For drivers that need to construct their own IRQ handler, the
three components are seen in the current handle_port -- i.e.
Rx, Tx and modem_status.

Make these exported symbols so that "almost" 8250 UARTs can
construct their own IRQ handler with these shared components,
while working around their own unique errata issues.

The function names are given a serial8250 prefix, since they
are now entering the global namespace.

Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
Acked-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/tty/serial/8250.c

@@ -1300,8 +1300,6 @@ static void serial8250_stop_tx(struct uart_port *port)
 	}
 }
 
-static void transmit_chars(struct uart_8250_port *up);
-
 static void serial8250_start_tx(struct uart_port *port)
 {
 	struct uart_8250_port *up =
@@ -1318,7 +1316,7 @@ static void serial8250_start_tx(struct uart_port *port)
 			if ((up->port.type == PORT_RM9000) ?
 				(lsr & UART_LSR_THRE) :
 				(lsr & UART_LSR_TEMT))
-				transmit_chars(up);
+				serial8250_tx_chars(up);
 		}
 	}
 
@@ -1376,12 +1374,12 @@ static void clear_rx_fifo(struct uart_8250_port *up)
 }
 
 /*
- * receive_chars: processes according to the passed in LSR
+ * serial8250_rx_chars: processes according to the passed in LSR
  * value, and returns the remaining LSR bits not handled
  * by this Rx routine.
  */
-static unsigned char
-receive_chars(struct uart_8250_port *up, unsigned char lsr)
+unsigned char
+serial8250_rx_chars(struct uart_8250_port *up, unsigned char lsr)
 {
 	struct tty_struct *tty = up->port.state->port.tty;
 	unsigned char ch;
@@ -1462,8 +1460,9 @@ ignore_char:
 	spin_lock(&up->port.lock);
 	return lsr;
 }
+EXPORT_SYMBOL_GPL(serial8250_rx_chars);
 
-static void transmit_chars(struct uart_8250_port *up)
+void serial8250_tx_chars(struct uart_8250_port *up)
 {
 	struct circ_buf *xmit = &up->port.state->xmit;
 	int count;
@@ -1500,8 +1499,9 @@ static void transmit_chars(struct uart_8250_port *up)
 	if (uart_circ_empty(xmit))
 		__stop_tx(up);
 }
+EXPORT_SYMBOL_GPL(serial8250_tx_chars);
 
-static unsigned int check_modem_status(struct uart_8250_port *up)
+unsigned int serial8250_modem_status(struct uart_8250_port *up)
 {
 	unsigned int status = serial_in(up, UART_MSR);
 
@@ -1523,6 +1523,7 @@ static unsigned int check_modem_status(struct uart_8250_port *up)
 
 	return status;
 }
+EXPORT_SYMBOL_GPL(serial8250_modem_status);
 
 /*
  * This handles the interrupt from one port.
@@ -1539,10 +1540,10 @@ static void serial8250_handle_port(struct uart_8250_port *up)
 	DEBUG_INTR("status = %x...", status);
 
 	if (status & (UART_LSR_DR | UART_LSR_BI))
-		status = receive_chars(up, status);
-	check_modem_status(up);
+		status = serial8250_rx_chars(up, status);
+	serial8250_modem_status(up);
 	if (status & UART_LSR_THRE)
-		transmit_chars(up);
+		serial8250_tx_chars(up);
 
 	spin_unlock_irqrestore(&up->port.lock, flags);
 }
@@ -1782,7 +1783,7 @@ static void serial8250_backup_timeout(unsigned long data)
 	}
 
 	if (!(iir & UART_IIR_NO_INT))
-		transmit_chars(up);
+		serial8250_tx_chars(up);
 
 	if (is_real_interrupt(up->port.irq))
 		serial_out(up, UART_IER, ier);
@@ -1816,7 +1817,7 @@ static unsigned int serial8250_get_mctrl(struct uart_port *port)
 	unsigned int status;
 	unsigned int ret;
 
-	status = check_modem_status(up);
+	status = serial8250_modem_status(up);
 
 	ret = 0;
 	if (status & UART_MSR_DCD)
@@ -2863,7 +2864,7 @@ serial8250_console_write(struct console *co, const char *s, unsigned int count)
 	 *	while processing with interrupts off.
 	 */
 	if (up->msr_saved_flags)
-		check_modem_status(up);
+		serial8250_modem_status(up);
 
 	if (locked)
 		spin_unlock(&up->port.lock);

include/linux/serial_8250.h

@@ -66,6 +66,7 @@ enum {
  * dependent on the 8250 driver.
  */
 struct uart_port;
+struct uart_8250_port;
 
 int serial8250_register_port(struct uart_port *);
 void serial8250_unregister_port(int line);
@@ -82,6 +83,9 @@ extern void serial8250_do_set_termios(struct uart_port *port,
 extern void serial8250_do_pm(struct uart_port *port, unsigned int state,
 			     unsigned int oldstate);
 int serial8250_handle_irq(struct uart_port *port, unsigned int iir);
+unsigned char serial8250_rx_chars(struct uart_8250_port *up, unsigned char lsr);
+void serial8250_tx_chars(struct uart_8250_port *up);
+unsigned int serial8250_modem_status(struct uart_8250_port *up);
 
 extern void serial8250_set_isa_configurator(void (*v)
 					(int port, struct uart_port *up,