[SERIAL] Make the number of UARTs registered configurable.

Also add a nr_uarts module option to the 8250 code to override
this, up to a maximum of CONFIG_SERIAL_8250_NR_UARTS

This should appease people who complain about a proliferation
of /dev/ttyS & /sysfs nodes whilst at the same time allowing
a single kernel image to support the rarer occasions of
lots of devices.

Signed-off-by: Dave Jones <davej@redhat.com>

3 files changed, 30 insertions, 10 deletions

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index acb010bb087b..0dc848bf0b56 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -998,6 +998,8 @@ running once the system is up.
 
         nowb            [ARM]
 
+        nr_uarts=       [SERIAL] maximum number of UARTs to be registered.
+
         opl3=           [HW,OSS]
                         Format: <io>
 
diff --git a/drivers/serial/8250.c b/drivers/serial/8250.c
index 1891cf5bdeef..e8454611cb65 100644
--- a/drivers/serial/8250.c
+++ b/drivers/serial/8250.c
@@ -54,6 +54,8 @@
  */
 static unsigned int share_irqs = SERIAL8250_SHARE_IRQS;
 
+static unsigned int nr_uarts = CONFIG_SERIAL_8250_RUNTIME_UARTS;
+
 /*
  * Debugging.
  */
@@ -2118,7 +2120,7 @@ static void __init serial8250_isa_init_ports(void)
                 return;
         first = 0;
 
-        for (i = 0; i < UART_NR; i++) {
+        for (i = 0; i < nr_uarts; i++) {
                 struct uart_8250_port *up = &serial8250_ports[i];
 
                 up->port.line = i;
@@ -2137,7 +2139,7 @@ static void __init serial8250_isa_init_ports(void)
         }
 
         for (i = 0, up = serial8250_ports;
-             i < ARRAY_SIZE(old_serial_port) && i < UART_NR;
+             i < ARRAY_SIZE(old_serial_port) && i < nr_uarts;
              i++, up++) {
                 up->port.iobase   = old_serial_port[i].port;
                 up->port.irq      = irq_canonicalize(old_serial_port[i].irq);
@@ -2159,7 +2161,7 @@ serial8250_register_ports(struct uart_driver *drv, struct device *dev)
 
         serial8250_isa_init_ports();
 
-        for (i = 0; i < UART_NR; i++) {
+        for (i = 0; i < nr_uarts; i++) {
                 struct uart_8250_port *up = &serial8250_ports[i];
 
                 up->port.dev = dev;
@@ -2262,7 +2264,7 @@ static int serial8250_console_setup(struct console *co, char *options)
          * if so, search for the first available port that does have
          * console support.
          */
-        if (co->index >= UART_NR)
+        if (co->index >= nr_uarts)
                 co->index = 0;
         port = &serial8250_ports[co->index].port;
         if (!port->iobase && !port->membase)
@@ -2298,7 +2300,7 @@ static int __init find_port(struct uart_port *p)
         int line;
         struct uart_port *port;
 
-        for (line = 0; line < UART_NR; line++) {
+        for (line = 0; line < nr_uarts; line++) {
                 port = &serial8250_ports[line].port;
                 if (uart_match_port(p, port))
                         return line;
@@ -2420,7 +2422,7 @@ static int __devexit serial8250_remove(struct platform_device *dev)
 {
         int i;
 
-        for (i = 0; i < UART_NR; i++) {
+        for (i = 0; i < nr_uarts; i++) {
                 struct uart_8250_port *up = &serial8250_ports[i];
 
                 if (up->port.dev == &dev->dev)
@@ -2487,7 +2489,7 @@ static struct uart_8250_port *serial8250_find_match_or_unused(struct uart_port *
         /*
          * First, find a port entry which matches.
          */
-        for (i = 0; i < UART_NR; i++)
+        for (i = 0; i < nr_uarts; i++)
                 if (uart_match_port(&serial8250_ports[i].port, port))
                         return &serial8250_ports[i];
 
@@ -2496,7 +2498,7 @@ static struct uart_8250_port *serial8250_find_match_or_unused(struct uart_port *
          * free entry.  We look for one which hasn't been previously
          * used (indicated by zero iobase).
          */
-        for (i = 0; i < UART_NR; i++)
+        for (i = 0; i < nr_uarts; i++)
                 if (serial8250_ports[i].port.type == PORT_UNKNOWN &&
                     serial8250_ports[i].port.iobase == 0)
                         return &serial8250_ports[i];
@@ -2505,7 +2507,7 @@ static struct uart_8250_port *serial8250_find_match_or_unused(struct uart_port *
          * That also failed.  Last resort is to find any entry which
          * doesn't have a real port associated with it.
          */
-        for (i = 0; i < UART_NR; i++)
+        for (i = 0; i < nr_uarts; i++)
                 if (serial8250_ports[i].port.type == PORT_UNKNOWN)
                         return &serial8250_ports[i];
 
@@ -2590,8 +2592,11 @@ static int __init serial8250_init(void)
 {
         int ret, i;
 
+        if (nr_uarts > UART_NR)
+                nr_uarts = UART_NR;
+
         printk(KERN_INFO "Serial: 8250/16550 driver $Revision: 1.90 $ "
-                "%d ports, IRQ sharing %sabled\n", (int) UART_NR,
+                "%d ports, IRQ sharing %sabled\n", nr_uarts,
                 share_irqs ? "en" : "dis");
 
         for (i = 0; i < NR_IRQS; i++)
@@ -2651,6 +2656,9 @@ module_param(share_irqs, uint, 0644);
 MODULE_PARM_DESC(share_irqs, "Share IRQs with other non-8250/16x50 devices"
         " (unsafe)");
 
+module_param(nr_uarts, uint, 0644);
+MODULE_PARM_DESC(nr_uarts, "Maximum number of UARTs supported. (1-" __MODULE_STRING(CONFIG_SERIAL_8250_NR_UARTS) ")");
+
 #ifdef CONFIG_SERIAL_8250_RSA
 module_param_array(probe_rsa, ulong, &probe_rsa_count, 0444);
 MODULE_PARM_DESC(probe_rsa, "Probe I/O ports for RSA");
diff --git a/drivers/serial/Kconfig b/drivers/serial/Kconfig
index 812bae62c8ec..3fd5b999fdac 100644
--- a/drivers/serial/Kconfig
+++ b/drivers/serial/Kconfig
@@ -95,6 +95,16 @@ config SERIAL_8250_NR_UARTS
           PCI enumeration and any ports that may be added at run-time
           via hot-plug, or any ISA multi-port serial cards.
 
+config SERIAL_8250_RUNTIME_UARTS
+        int "Number of 8250/16550 serial ports to register at runtime"
+        depends on SERIAL_8250
+        default "4"
+        help
+          Set this to the maximum number of serial ports you want
+          the kernel to register at boot time.  This can be overriden
+          with the module parameter "nr_uarts", or boot-time parameter
+          8250.nr_uarts
+
 config SERIAL_8250_EXTENDED
         bool "Extended 8250/16550 serial driver options"
         depends on SERIAL_8250