powerpc/pseries: Add pseries update notifier for OFDT prop changes

This adds an update notifier mechanism for changes to properties in the
device tree.  One use of this would be a device driver that needs to act
on changes to it's properties in the device tree after a live migration
or a dynamic activation that is triggered by updates to ofdt properties.

Signed-off-by: Robert Jennings <rcj@linux.vnet.ibm.com>
Signed-off-by: Kent Yoder <key@linux.vnet.ibm.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

arch/powerpc/include/asm/pSeries_reconfig.h

@@ -13,6 +13,18 @@
 #define PSERIES_RECONFIG_REMOVE		0x0002
 #define PSERIES_DRCONF_MEM_ADD		0x0003
 #define PSERIES_DRCONF_MEM_REMOVE	0x0004
+#define PSERIES_UPDATE_PROPERTY		0x0005
+
+/**
+ * pSeries_reconfig_notify - Notifier value structure for OFDT property updates
+ *
+ * @node: Device tree node which owns the property being updated
+ * @property: Updated property
+ */
+struct pSeries_reconfig_prop_update {
+	struct device_node *node;
+	struct property *property;
+};
 
 #ifdef CONFIG_PPC_PSERIES
 extern int pSeries_reconfig_notifier_register(struct notifier_block *);

arch/powerpc/platforms/pseries/reconfig.c

@@ -103,11 +103,13 @@ int pSeries_reconfig_notifier_register(struct notifier_block *nb)
 {
 	return blocking_notifier_chain_register(&pSeries_reconfig_chain, nb);
 }
+EXPORT_SYMBOL_GPL(pSeries_reconfig_notifier_register);
 
 void pSeries_reconfig_notifier_unregister(struct notifier_block *nb)
 {
 	blocking_notifier_chain_unregister(&pSeries_reconfig_chain, nb);
 }
+EXPORT_SYMBOL_GPL(pSeries_reconfig_notifier_unregister);
 
 int pSeries_reconfig_notify(unsigned long action, void *p)
 {
@@ -426,6 +428,7 @@ static int do_remove_property(char *buf, size_t bufsize)
 static int do_update_property(char *buf, size_t bufsize)
 {
 	struct device_node *np;
+	struct pSeries_reconfig_prop_update upd_value;
 	unsigned char *value;
 	char *name, *end, *next_prop;
 	int rc, length;
@@ -454,6 +457,10 @@ static int do_update_property(char *buf, size_t bufsize)
 		return -ENODEV;
 	}
 
+	upd_value.node = np;
+	upd_value.property = newprop;
+	pSeries_reconfig_notify(PSERIES_UPDATE_PROPERTY, &upd_value);
+
 	rc = prom_update_property(np, newprop, oldprop);
 	if (rc)
 		return rc;