char: xillybus: make xillybus_class a static const structure

Now that the driver core allows for struct class to be in read-only
memory, move the xillybus_class structure to be declared at build time
placing it into read-only memory, instead of having to be dynamically
allocated at load time.

Cc: Eli Billauer <eli.billauer@gmail.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Suggested-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Ivan Orlov <ivan.orlov0322@gmail.com>
Acked-by: Eli Billauer <eli.billauer@gmail.com>
Link: https://lore.kernel.org/r/20230620143751.578239-18-gregkh@linuxfoundation.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: ivanorlov2206

drivers/char/xillybus/xillybus_class.c

@@ -23,7 +23,9 @@ MODULE_LICENSE("GPL v2");
 
 static DEFINE_MUTEX(unit_mutex);
 static LIST_HEAD(unit_list);
-static struct class *xillybus_class;
+static const struct class xillybus_class = {
+	.name = "xillybus",
+};
 
 #define UNITNAMELEN 16
 
@@ -121,7 +123,7 @@ int xillybus_init_chrdev(struct device *dev,
 		len -= namelen + 1;
 		idt += namelen + 1;
 
-		device = device_create(xillybus_class,
+		device = device_create(&xillybus_class,
 				       NULL,
 				       MKDEV(unit->major,
 					     i + unit->lowest_minor),
@@ -152,7 +154,7 @@ int xillybus_init_chrdev(struct device *dev,
 
 unroll_device_create:
 	for (i--; i >= 0; i--)
-		device_destroy(xillybus_class, MKDEV(unit->major,
+		device_destroy(&xillybus_class, MKDEV(unit->major,
 						     i + unit->lowest_minor));
 
 	cdev_del(unit->cdev);
@@ -193,7 +195,7 @@ void xillybus_cleanup_chrdev(void *private_data,
 	for (minor = unit->lowest_minor;
 	     minor < (unit->lowest_minor + unit->num_nodes);
 	     minor++)
-		device_destroy(xillybus_class, MKDEV(unit->major, minor));
+		device_destroy(&xillybus_class, MKDEV(unit->major, minor));
 
 	cdev_del(unit->cdev);
 
@@ -242,19 +244,12 @@ EXPORT_SYMBOL(xillybus_find_inode);
 
 static int __init xillybus_class_init(void)
 {
-	xillybus_class = class_create("xillybus");
-
-	if (IS_ERR(xillybus_class)) {
-		pr_warn("Failed to register xillybus class\n");
-
-		return PTR_ERR(xillybus_class);
-	}
-	return 0;
+	return class_register(&xillybus_class);
 }
 
 static void __exit xillybus_class_exit(void)
 {
-	class_destroy(xillybus_class);
+	class_unregister(&xillybus_class);
 }
 
 module_init(xillybus_class_init);