Add a bus_null_rescan() method that always fails with an error.

Use this in place of kobj_error_method to disable BUS_RESCAN() on
PCI drivers that do not use the "standard" scanning algorithm.

sys/dev/cardbus/cardbus.c

@@ -346,7 +346,7 @@ static device_method_t cardbus_methods[] = {
 	DEVMETHOD(bus_get_dma_tag,	bus_generic_get_dma_tag),
 	DEVMETHOD(bus_read_ivar,	cardbus_read_ivar),
 	DEVMETHOD(bus_driver_added,	cardbus_driver_added),
-	DEVMETHOD(bus_rescan,		kobj_error_method),
+	DEVMETHOD(bus_rescan,		bus_null_rescan),
 
 	/* Card Interface */
 	DEVMETHOD(card_attach_card,	cardbus_attach_card),

sys/kern/subr_bus.c

@@ -4289,6 +4289,19 @@ bus_generic_get_domain(device_t dev, device_t child, int *domain)
 	return (ENOENT);
 }
 
+/**
+ * @brief Helper function for implementing BUS_RESCAN().
+ *
+ * This null implementation of BUS_RESCAN() always fails to indicate
+ * the bus does not support rescanning.
+ */
+int
+bus_null_rescan(device_t dev)
+{
+
+	return (ENXIO);
+}
+
 /*
  * Some convenience functions to make it easier for drivers to use the
  * resource-management functions.  All these really do is hide the

sys/mips/nlm/xlp_pci.c

@@ -154,7 +154,7 @@ static device_method_t xlp_pci_methods[] = {
 	/* Device interface */
 	DEVMETHOD(device_probe,		xlp_pci_probe),
 	DEVMETHOD(device_attach,	xlp_pci_attach),
-	DEVMETHOD(bus_rescan,		kobj_error_method),
+	DEVMETHOD(bus_rescan,		bus_null_rescan),
 	DEVMETHOD_END
 };
 

sys/powerpc/ofw/ofw_pcibus.c

@@ -77,7 +77,7 @@ static device_method_t ofw_pcibus_methods[] = {
 	/* Bus interface */
 	DEVMETHOD(bus_child_deleted,	ofw_pcibus_child_deleted),
 	DEVMETHOD(bus_child_pnpinfo_str, ofw_pcibus_child_pnpinfo_str_method),
-	DEVMETHOD(bus_rescan,		kobj_error_method),
+	DEVMETHOD(bus_rescan,		bus_null_rescan),
 
 	/* PCI interface */
 	DEVMETHOD(pci_alloc_devinfo,	ofw_pcibus_alloc_devinfo),

sys/sparc64/pci/ofw_pcibus.c

@@ -81,7 +81,7 @@ static device_method_t ofw_pcibus_methods[] = {
 	/* Bus interface */
 	DEVMETHOD(bus_child_deleted,	ofw_pcibus_child_deleted),
 	DEVMETHOD(bus_child_pnpinfo_str, ofw_pcibus_pnpinfo_str),
-	DEVMETHOD(bus_rescan,		kobj_error_method),
+	DEVMETHOD(bus_rescan,		bus_null_rescan),
 
 	/* PCI interface */
 	DEVMETHOD(pci_alloc_devinfo,	ofw_pcibus_alloc_devinfo),

sys/sys/bus.h

@@ -430,6 +430,7 @@ int	bus_generic_teardown_intr(device_t dev, device_t child,
 				  struct resource *irq, void *cookie);
 int	bus_generic_write_ivar(device_t dev, device_t child, int which,
 			       uintptr_t value);
+int	bus_null_rescan(device_t dev);
 
 /*
  * Wrapper functions for the BUS_*_RESOURCE methods to make client code