sysfs: Add attribute array to sysdev classes

Add a attribute array that is automatically registered and unregistered
to struct sysdev_class. This is similar to what struct class has.

A lot of drivers add list of attributes, so it's better to do 
this easily in the common sysdev layer.

This adds a new field to struct sysdev_class. I audited the 
whole tree and there are no dynamically allocated sysdev classes,
so this is fully compatible. 
Signed-off-by: NAndi Kleen <ak@linux.intel.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>

drivers/base/sys.c

@@ -145,13 +145,20 @@ int sysdev_class_register(struct sysdev_class *cls)
 	if (retval)
 		return retval;
 
-	return kset_register(&cls->kset);
+	retval = kset_register(&cls->kset);
+	if (!retval && cls->attrs)
+		retval = sysfs_create_files(&cls->kset.kobj,
+					    (const struct attribute **)cls->attrs);
+	return retval;
 }
 
 void sysdev_class_unregister(struct sysdev_class *cls)
 {
 	pr_debug("Unregistering sysdev class '%s'\n",
 		 kobject_name(&cls->kset.kobj));
+	if (cls->attrs)
+		sysfs_remove_files(&cls->kset.kobj,
+				   (const struct attribute **)cls->attrs);
 	kset_unregister(&cls->kset);
 }
 

include/linux/sysdev.h

@@ -27,10 +27,12 @@
 
 
 struct sys_device;
+struct sysdev_class_attribute;
 
 struct sysdev_class {
 	const char *name;
 	struct list_head	drivers;
+	struct sysdev_class_attribute **attrs;
 
 	/* Default operations for these types of devices */
 	int	(*shutdown)(struct sys_device *);