of/device: Add OF style matching helper function

Add of_driver_match_device() helper function.  This function can be used
by bus types to determine if a driver works with a device when using OF
style matching.  If CONFIG_OF is unselected, then it is a nop.

Signed-off-by: Grant Likely <grant.likely@secretlab.ca>
CC: Greg Kroah-Hartman <gregkh@suse.de>
CC: Michal Simek <monstr@monstr.eu>
CC: Grant Likely <grant.likely@secretlab.ca>
CC: Benjamin Herrenschmidt <benh@kernel.crashing.org>
CC: Stephen Rothwell <sfr@canb.auug.org.au>
CC: linux-kernel@vger.kernel.org
CC: microblaze-uclinux@itee.uq.edu.au
CC: linuxppc-dev@ozlabs.org
CC: devicetree-discuss@lists.ozlabs.org

drivers/of/device.c

@@ -20,7 +20,7 @@
 const struct of_device_id *of_match_device(const struct of_device_id *matches,
 					   const struct device *dev)
 {
-	if (!dev->of_node)
+	if ((!matches) || (!dev->of_node))
 		return NULL;
 	return of_match_node(matches, dev->of_node);
 }

include/linux/of_device.h

@@ -30,6 +30,17 @@
 extern const struct of_device_id *of_match_device(
 	const struct of_device_id *matches, const struct device *dev);
 
+/**
+ * of_driver_match_device - Tell if a driver's of_match_table matches a device.
+ * @drv: the device_driver structure to test
+ * @dev: the device structure to match against
+ */
+static inline int of_driver_match_device(const struct device *dev,
+					 const struct device_driver *drv)
+{
+	return of_match_device(drv->of_match_table, dev) != NULL;
+}
+
 extern struct of_device *of_dev_get(struct of_device *dev);
 extern void of_dev_put(struct of_device *dev);
 
@@ -48,6 +59,14 @@ extern ssize_t of_device_get_modalias(struct device *dev,
 extern int of_device_uevent(struct device *dev, struct kobj_uevent_env *env);
 
 
+#else /* CONFIG_OF_DEVICE */
+
+static inline int of_driver_match_device(struct device *dev,
+					 struct device_driver *drv)
+{
+	return 0;
+}
+
 #endif /* CONFIG_OF_DEVICE */
 
 #endif /* _LINUX_OF_DEVICE_H */