nubus: Call bus_register unconditionally

Loading a NuBus driver module on a non-NuBus machine triggers the
BUG_ON(!drv->bus->p) in driver_register(), because bus_register() was
not called, because it is conditional on MACH_IS_MAC.

Fix the crash by calling bus_register() unconditionally. Call it from
a postcore_initcall(), like other busses do.

Hence, the bus type is available for device_register(), which happens
in a subsys initcall, and for driver_register(), which happens in a
device or module initcall.

Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reported-by: Michael Schmitz <schmitzmic@gmail.com>
Tested-by: Stan Johnson <userm57@yahoo.com>
Fixes: 7f86c765a6a2 ("nubus: Add support for the driver model")
Signed-off-by: Finn Thain <fthain@telegraphics.com.au>
Reviewed-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/nubus/bus.c

@@ -63,20 +63,15 @@ static struct device nubus_parent = {
 	.init_name	= "nubus",
 };
 
-int __init nubus_bus_register(void)
+static int __init nubus_bus_register(void)
 {
-	int err;
-
-	err = device_register(&nubus_parent);
-	if (err)
-		return err;
-
-	err = bus_register(&nubus_bus_type);
-	if (!err)
-		return 0;
+	return bus_register(&nubus_bus_type);
+}
+postcore_initcall(nubus_bus_register);
 
-	device_unregister(&nubus_parent);
-	return err;
+int __init nubus_parent_device_register(void)
+{
+	return device_register(&nubus_parent);
 }
 
 static void nubus_device_release(struct device *dev)

drivers/nubus/nubus.c

@@ -875,7 +875,7 @@ static int __init nubus_init(void)
 		return 0;
 
 	nubus_proc_init();
-	err = nubus_bus_register();
+	err = nubus_parent_device_register();
 	if (err)
 		return err;
 	nubus_scan_bus();

include/linux/nubus.h

@@ -163,7 +163,7 @@ void nubus_seq_write_rsrc_mem(struct seq_file *m,
 unsigned char *nubus_dirptr(const struct nubus_dirent *nd);
 
 /* Declarations relating to driver model objects */
-int nubus_bus_register(void);
+int nubus_parent_device_register(void);
 int nubus_device_register(struct nubus_board *board);
 int nubus_driver_register(struct nubus_driver *ndrv);
 void nubus_driver_unregister(struct nubus_driver *ndrv);