driver core: class: remove dev_kobj from struct class

The dev_kobj field in struct class is now only written to, but never
read from, so it can be removed as it is useless.
Acked-by: Rafael J. Wysocki <rafael@kernel.org>
Link: https://lore.kernel.org/r/20230331093318.82288-5-gregkh@linuxfoundation.orgSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

block/genhd.c

@@ -899,7 +899,6 @@ static int __init genhd_device_init(void)
 {
 	int error;
 
-	block_class.dev_kobj = sysfs_dev_block_kobj;
 	error = class_register(&block_class);
 	if (unlikely(error))
 		return error;

drivers/base/class.c

@@ -197,10 +197,6 @@ int class_register(struct class *cls)
 		return error;
 	}
 
-	/* set the default /sys/dev directory for devices of this class */
-	if (!cls->dev_kobj)
-		cls->dev_kobj = sysfs_dev_char_kobj;
-
 	cp->subsys.kobj.kset = class_kset;
 	cp->subsys.kobj.ktype = &class_ktype;
 	cp->class = cls;

include/linux/device/class.h

@@ -27,7 +27,6 @@ struct fwnode_handle;
  * @name:	Name of the 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
  *		few other things that generate uevents to add the environment
  *		variables.
@@ -55,7 +54,6 @@ struct class {
 
 	const struct attribute_group	**class_groups;
 	const struct attribute_group	**dev_groups;
-	struct kobject			*dev_kobj;
 
 	int (*dev_uevent)(const struct device *dev, struct kobj_uevent_env *env);
 	char *(*devnode)(const struct device *dev, umode_t *mode);