misc: phantom: make phantom_class constant

Now that the driver core allows for struct class to be in read-only
memory, we should make all 'class' structures declared at build time
placing them into read-only memory, instead of having to be dynamically
allocated at runtime.

Cc: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Jiri Slaby <jirislaby@kernel.org>
Link: https://lore.kernel.org/r/2023102434-font-feast-98e3@gregkh
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: gregkh

drivers/misc/phantom.c

@@ -35,9 +35,12 @@
 #define PHB_NOT_OH		2
 
 static DEFINE_MUTEX(phantom_mutex);
-static struct class *phantom_class;
 static int phantom_major;
 
+static const struct class phantom_class = {
+	.name = "phantom",
+};
+
 struct phantom_device {
 	unsigned int opened;
 	void __iomem *caddr;
@@ -403,7 +406,7 @@ static int phantom_probe(struct pci_dev *pdev,
 		goto err_irq;
 	}
 
-	if (IS_ERR(device_create(phantom_class, &pdev->dev,
+	if (IS_ERR(device_create(&phantom_class, &pdev->dev,
 				 MKDEV(phantom_major, minor), NULL,
 				 "phantom%u", minor)))
 		dev_err(&pdev->dev, "can't create device\n");
@@ -436,7 +439,7 @@ static void phantom_remove(struct pci_dev *pdev)
 	struct phantom_device *pht = pci_get_drvdata(pdev);
 	unsigned int minor = MINOR(pht->cdev.dev);
 
-	device_destroy(phantom_class, MKDEV(phantom_major, minor));
+	device_destroy(&phantom_class, MKDEV(phantom_major, minor));
 
 	cdev_del(&pht->cdev);
 
@@ -503,13 +506,12 @@ static int __init phantom_init(void)
 	int retval;
 	dev_t dev;
 
-	phantom_class = class_create("phantom");
-	if (IS_ERR(phantom_class)) {
-		retval = PTR_ERR(phantom_class);
+	retval = class_register(&phantom_class);
+	if (retval) {
 		printk(KERN_ERR "phantom: can't register phantom class\n");
 		goto err;
 	}
-	retval = class_create_file(phantom_class, &class_attr_version.attr);
+	retval = class_create_file(&phantom_class, &class_attr_version.attr);
 	if (retval) {
 		printk(KERN_ERR "phantom: can't create sysfs version file\n");
 		goto err_class;
@@ -535,9 +537,9 @@ static int __init phantom_init(void)
 err_unchr:
 	unregister_chrdev_region(dev, PHANTOM_MAX_MINORS);
 err_attr:
-	class_remove_file(phantom_class, &class_attr_version.attr);
+	class_remove_file(&phantom_class, &class_attr_version.attr);
 err_class:
-	class_destroy(phantom_class);
+	class_unregister(&phantom_class);
 err:
 	return retval;
 }
@@ -548,8 +550,8 @@ static void __exit phantom_exit(void)
 
 	unregister_chrdev_region(MKDEV(phantom_major, 0), PHANTOM_MAX_MINORS);
 
-	class_remove_file(phantom_class, &class_attr_version.attr);
-	class_destroy(phantom_class);
+	class_remove_file(&phantom_class, &class_attr_version.attr);
+	class_unregister(&phantom_class);
 
 	pr_debug("phantom: module successfully removed\n");
 }