[PATCH v2 1/3] serial: 8250: allow use of non-runtime configured uart ports

["Martin Hundebøll" <martin@geanix.com>]

The logic to find unused ports when registering new 8250 uart ports
searches only up to CONFIG_SERIAL_8250_RUNTIME_UARTS, which forces users
of external 8250 ports to increase the number of runtime ports
artificially.

Fix this by initializing each allocated port structure with basic
settings like line number and uart operation callbacks, and by searching
the entire array of allocated ports to find an unused one.

Signed-off-by: Martin Hundebøll <martin@geanix.com>
---
 drivers/tty/serial/8250/8250_core.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/drivers/tty/serial/8250/8250_core.c b/drivers/tty/serial/8250/8250_core.c
index 94fbf0add2ce..a166cc66e7d1 100644
--- a/drivers/tty/serial/8250/8250_core.c
+++ b/drivers/tty/serial/8250/8250_core.c
@@ -500,7 +500,7 @@ static void __init serial8250_isa_init_ports(void)
 	if (nr_uarts > UART_NR)
 		nr_uarts = UART_NR;
 
-	for (i = 0; i < nr_uarts; i++) {
+	for (i = 0; i < UART_NR; i++) {
 		struct uart_8250_port *up = &serial8250_ports[i];
 		struct uart_port *port = &up->port;
 
@@ -926,15 +926,16 @@ static struct uart_8250_port *serial8250_find_match_or_unused(const struct uart_
 
 	/* try line number first if still available */
 	i = port->line;
-	if (i < nr_uarts && serial8250_ports[i].port.type == PORT_UNKNOWN &&
+	if (i < UART_NR && serial8250_ports[i].port.type == PORT_UNKNOWN &&
 			serial8250_ports[i].port.iobase == 0)
 		return &serial8250_ports[i];
+
 	/*
 	 * We didn't find a matching entry, so look for the first
 	 * free entry.  We look for one which hasn't been previously
 	 * used (indicated by zero iobase).
 	 */
-	for (i = 0; i < nr_uarts; i++)
+	for (i = 0; i < UART_NR; i++)
 		if (serial8250_ports[i].port.type == PORT_UNKNOWN &&
 		    serial8250_ports[i].port.iobase == 0)
 			return &serial8250_ports[i];
@@ -943,7 +944,7 @@ static struct uart_8250_port *serial8250_find_match_or_unused(const struct uart_
 	 * That also failed.  Last resort is to find any entry which
 	 * doesn't have a real port associated with it.
 	 */
-	for (i = 0; i < nr_uarts; i++)
+	for (i = 0; i < UART_NR; i++)
 		if (serial8250_ports[i].port.type == PORT_UNKNOWN)
 			return &serial8250_ports[i];
 
-- 
2.38.0