s390/cio: add test for ccwgroup device

Add a test to check if a given device is a ccwgroup device.
Signed-off-by: Sebastian Ott <sebott@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

arch/s390/include/asm/ccwgroup.h

@@ -73,4 +73,14 @@ extern void ccwgroup_remove_ccwdev(struct ccw_device *cdev);
 
 #define to_ccwgroupdev(x) container_of((x), struct ccwgroup_device, dev)
 #define to_ccwgroupdrv(x) container_of((x), struct ccwgroup_driver, driver)
+
+#if IS_ENABLED(CONFIG_CCWGROUP)
+bool dev_is_ccwgroup(struct device *dev);
+#else /* CONFIG_CCWGROUP */
+static inline bool dev_is_ccwgroup(struct device *dev)
+{
+	return false;
+}
+#endif /* CONFIG_CCWGROUP */
+
 #endif

drivers/s390/cio/ccwgroup.c

@@ -561,6 +561,12 @@ static struct bus_type ccwgroup_bus_type = {
 	.pm = &ccwgroup_pm_ops,
 };
 
+bool dev_is_ccwgroup(struct device *dev)
+{
+	return dev->bus == &ccwgroup_bus_type;
+}
+EXPORT_SYMBOL(dev_is_ccwgroup);
+
 /**
  * ccwgroup_driver_register() - register a ccw group driver
  * @cdriver: driver to be registered