[POWERPC] Optionally use new device number for pmac_zilog

This adds the option for the pmac_zilog driver to use the major/minor
numbers recently allocated specifically for it (/dev/ttyPZn) instead
of the /dev/ttySn numbers.  The advantage of doing this is that it
allows the pmac_zilog and 8250 drivers to coexist.  The disadvantage
of doing this is that it is a user-visible ABI change and it will
break existing working setups on powermacs, and could be confusing to
users.

Signed-off-by: David Woodhouse <dwmw2@infradead.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>

drivers/serial/Kconfig

@@ -986,6 +986,31 @@ config SERIAL_PMACZILOG
 	  PowerMac machines.
 	  Say Y or M if you want to be able to these serial ports.
 
+config SERIAL_PMACZILOG_TTYS
+	bool "Use ttySn device nodes for Zilog z85c30"
+	depends on SERIAL_PMACZILOG
+	help
+	  The pmac_zilog driver for the z85C30 chip on many powermacs
+	  historically used the device numbers for /dev/ttySn.  The
+	  8250 serial port driver also uses these numbers, which means
+	  the two drivers being unable to coexist; you could not use
+	  both z85C30 and 8250 type ports at the same time.
+
+	  If this option is not selected, the pmac_zilog driver will
+	  use the device numbers allocated for /dev/ttyPZn.  This allows
+	  the pmac_zilog and 8250 drivers to co-exist, but may cause
+	  existing userspace setups to break.  Programs that need to
+	  access the built-in serial ports on powermacs will need to
+	  be reconfigured to use /dev/ttyPZn instead of /dev/ttySn.
+
+	  If you enable this option, any z85c30 ports in the system will
+	  be registered as ttyS0 onwards as in the past, and you will be
+	  unable to use the 8250 module for PCMCIA or other 16C550-style
+	  UARTs.
+
+	  Say N unless you need the z85c30 ports on your powermac
+	  to appear as /dev/ttySn.
+
 config SERIAL_PMACZILOG_CONSOLE
 	bool "Console on PowerMac z85c30 serial port"
 	depends on SERIAL_PMACZILOG=y

drivers/serial/pmac_zilog.c

@@ -88,6 +88,16 @@ MODULE_LICENSE("GPL");
 
 #define PWRDBG(fmt, arg...)	printk(KERN_DEBUG fmt , ## arg)
 
+#ifdef CONFIG_SERIAL_PMACZILOG_TTYS
+#define PMACZILOG_MAJOR		TTY_MAJOR
+#define PMACZILOG_MINOR		64
+#define PMACZILOG_NAME		"ttyS"
+#else
+#define PMACZILOG_MAJOR		204
+#define PMACZILOG_MINOR		192
+#define PMACZILOG_NAME		"ttyPZ"
+#endif
+
 
 /*
  * For the sake of early serial console, we can do a pre-probe
@@ -99,9 +109,10 @@ static DEFINE_MUTEX(pmz_irq_mutex);
 
 static struct uart_driver pmz_uart_reg = {
 	.owner		=	THIS_MODULE,
-	.driver_name	=	"ttyS",
-	.dev_name	=	"ttyS",
-	.major		=	TTY_MAJOR,
+	.driver_name	=	PMACZILOG_NAME,
+	.dev_name	=	PMACZILOG_NAME,
+	.major		=	PMACZILOG_MAJOR,
+	.minor		=	PMACZILOG_MINOR,
 };
 
 
@@ -1778,7 +1789,7 @@ static void pmz_console_write(struct console *con, const char *s, unsigned int c
 static int __init pmz_console_setup(struct console *co, char *options);
 
 static struct console pmz_console = {
-	.name	=	"ttyS",
+	.name	=	PMACZILOG_NAME,
 	.write	=	pmz_console_write,
 	.device	=	uart_console_device,
 	.setup	=	pmz_console_setup,
@@ -1802,7 +1813,6 @@ static int __init pmz_register(void)
 
 	pmz_uart_reg.nr = pmz_ports_count;
 	pmz_uart_reg.cons = PMACZILOG_CONSOLE;
-	pmz_uart_reg.minor = 64;
 
 	/*
 	 * Register this driver with the serial core