s390/vmlogrdr: make vmlogrdr_class constant

Since commit 43a7206 ("driver core: class: make class_register() take
a const *"), the driver core allows for struct class to be in read-only
memory, so move the vmlogrdr_class structure to be declared at build time
placing it into read-only memory, instead of having to be dynamically
allocated at boot time.

Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Suggested-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: "Ricardo B. Marliere" <ricardo@marliere.net>
Link: https://lore.kernel.org/r/20240305-class_cleanup-s390-v1-3-c4ff1ec49ffd@marliere.net
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>

Author: rbmarliere

drivers/s390/char/vmlogrdr.c

@@ -679,7 +679,9 @@ static const struct attribute_group *vmlogrdr_attr_groups[] = {
 	NULL,
 };
 
-static struct class *vmlogrdr_class;
+static const struct class vmlogrdr_class = {
+	.name = "vmlogrdr_class",
+};
 static struct device_driver vmlogrdr_driver = {
 	.name = "vmlogrdr",
 	.bus  = &iucv_bus,
@@ -699,12 +701,9 @@ static int vmlogrdr_register_driver(void)
 	if (ret)
 		goto out_iucv;
 
-	vmlogrdr_class = class_create("vmlogrdr");
-	if (IS_ERR(vmlogrdr_class)) {
-		ret = PTR_ERR(vmlogrdr_class);
-		vmlogrdr_class = NULL;
+	ret = class_register(&vmlogrdr_class);
+	if (ret)
 		goto out_driver;
-	}
 	return 0;
 
 out_driver:
@@ -718,8 +717,7 @@ static int vmlogrdr_register_driver(void)
 
 static void vmlogrdr_unregister_driver(void)
 {
-	class_destroy(vmlogrdr_class);
-	vmlogrdr_class = NULL;
+	class_unregister(&vmlogrdr_class);
 	driver_unregister(&vmlogrdr_driver);
 	iucv_unregister(&vmlogrdr_iucv_handler, 1);
 }
@@ -754,7 +752,7 @@ static int vmlogrdr_register_device(struct vmlogrdr_priv_t *priv)
 		return ret;
 	}
 
-	priv->class_device = device_create(vmlogrdr_class, dev,
+	priv->class_device = device_create(&vmlogrdr_class, dev,
 					   MKDEV(vmlogrdr_major,
 						 priv->minor_num),
 					   priv, "%s", dev_name(dev));
@@ -771,7 +769,7 @@ static int vmlogrdr_register_device(struct vmlogrdr_priv_t *priv)
 
 static int vmlogrdr_unregister_device(struct vmlogrdr_priv_t *priv)
 {
-	device_destroy(vmlogrdr_class, MKDEV(vmlogrdr_major, priv->minor_num));
+	device_destroy(&vmlogrdr_class, MKDEV(vmlogrdr_major, priv->minor_num));
 	if (priv->device != NULL) {
 		device_unregister(priv->device);
 		priv->device=NULL;