ppdev: make ppdev_class a static const structure

Now that the driver core allows for struct class to be in read-only
memory, move the ppdev_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: Sudip Mukherjee <sudipm.mukherjee@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>
Link: https://lore.kernel.org/r/20230620143751.578239-15-gregkh@linuxfoundation.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: ivanorlov2206

drivers/char/ppdev.c

@@ -773,7 +773,9 @@ static __poll_t pp_poll(struct file *file, poll_table *wait)
 	return mask;
 }
 
-static struct class *ppdev_class;
+static const struct class ppdev_class = {
+	.name = CHRDEV,
+};
 
 static const struct file_operations pp_fops = {
 	.owner		= THIS_MODULE,
@@ -794,7 +796,7 @@ static void pp_attach(struct parport *port)
 	if (devices[port->number])
 		return;
 
-	ret = device_create(ppdev_class, port->dev,
+	ret = device_create(&ppdev_class, port->dev,
 			    MKDEV(PP_MAJOR, port->number), NULL,
 			    "parport%d", port->number);
 	if (IS_ERR(ret)) {
@@ -810,7 +812,7 @@ static void pp_detach(struct parport *port)
 	if (!devices[port->number])
 		return;
 
-	device_destroy(ppdev_class, MKDEV(PP_MAJOR, port->number));
+	device_destroy(&ppdev_class, MKDEV(PP_MAJOR, port->number));
 	devices[port->number] = NULL;
 }
 
@@ -841,11 +843,10 @@ static int __init ppdev_init(void)
 		pr_warn(CHRDEV ": unable to get major %d\n", PP_MAJOR);
 		return -EIO;
 	}
-	ppdev_class = class_create(CHRDEV);
-	if (IS_ERR(ppdev_class)) {
-		err = PTR_ERR(ppdev_class);
+	err = class_register(&ppdev_class);
+	if (err)
 		goto out_chrdev;
-	}
+
 	err = parport_register_driver(&pp_driver);
 	if (err < 0) {
 		pr_warn(CHRDEV ": unable to register with parport\n");
@@ -856,7 +857,7 @@ static int __init ppdev_init(void)
 	goto out;
 
 out_class:
-	class_destroy(ppdev_class);
+	class_unregister(&ppdev_class);
 out_chrdev:
 	unregister_chrdev(PP_MAJOR, CHRDEV);
 out:
@@ -867,7 +868,7 @@ static void __exit ppdev_cleanup(void)
 {
 	/* Clean up all parport stuff */
 	parport_unregister_driver(&pp_driver);
-	class_destroy(ppdev_class);
+	class_unregister(&ppdev_class);
 	unregister_chrdev(PP_MAJOR, CHRDEV);
 }