driver core: class: add class_groups support

struct class needs to have a set of default groups that are added, as
adding individual attributes does not work well in the long run. So add
support for that.

Future patches will convert the existing usages of class_attrs to use
class_groups and then class_attrs will go away.

Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/base/class.c

···
 	put_device(dev);
 }
 
+static int class_add_groups(struct class *cls,
+			    const struct attribute_group **groups)
+{
+	return sysfs_create_groups(&cls->p->subsys.kobj, groups);
+}
+
+static void class_remove_groups(struct class *cls,
+				const struct attribute_group **groups)
+{
+	return sysfs_remove_groups(&cls->p->subsys.kobj, groups);
+}
+
 int __class_register(struct class *cls, struct lock_class_key *key)
 {
 	struct subsys_private *cp;
···
 		kfree(cp);
 		return error;
 	}
+	error = class_add_groups(class_get(cls), cls->class_groups);
+	class_put(cls);
 	error = add_class_attrs(class_get(cls));
 	class_put(cls);
 	return error;
···
 {
 	pr_debug("device class '%s': unregistering\n", cls->name);
 	remove_class_attrs(cls);
+	class_remove_groups(cls, cls->class_groups);
 	kset_unregister(&cls->p->subsys);
 }
 

include/linux/device.h

···
  * @name:	Name of the class.
  * @owner:	The module owner.
  * @class_attrs: Default attributes of this class.
+ * @class_groups: Default attributes of this class.
  * @dev_groups:	Default attributes of the devices that belong to the class.
  * @dev_kobj:	The kobject that represents this class and links it into the hierarchy.
  * @dev_uevent:	Called when a device is added, removed from this class, or a
···
 	struct module		*owner;
 
 	struct class_attribute		*class_attrs;
+	const struct attribute_group	**class_groups;
 	const struct attribute_group	**dev_groups;
 	struct kobject			*dev_kobj;