USB: gadget: f_printer: make usb_gadget_class a static const structure

Now that the driver core allows for struct class to be in read-only
memory, move the usb_gadget_class structure to be declared at build time
placing it into read-only memory, instead of having to be dynamically
allocated at load time.
Suggested-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Ivan Orlov <ivan.orlov0322@gmail.com>
Link: https://lore.kernel.org/r/20230620094412.508580-10-gregkh@linuxfoundation.orgSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/gadget/function/f_printer.c

@@ -54,7 +54,10 @@
 #define DEFAULT_Q_LEN		10 /* same as legacy g_printer gadget */
 
 static int major, minors;
-static struct class *usb_gadget_class;
+static const struct class usb_gadget_class = {
+	.name = "usb_printer_gadget",
+};
+
 static DEFINE_IDA(printer_ida);
 static DEFINE_MUTEX(printer_ida_lock); /* protects access do printer_ida */
 
@@ -1120,7 +1123,7 @@ static int printer_func_bind(struct usb_configuration *c,
 
 	/* Setup the sysfs files for the printer gadget. */
 	devt = MKDEV(major, dev->minor);
-	pdev = device_create(usb_gadget_class, NULL, devt,
+	pdev = device_create(&usb_gadget_class, NULL, devt,
 				  NULL, "g_printer%d", dev->minor);
 	if (IS_ERR(pdev)) {
 		ERROR(dev, "Failed to create device: g_printer\n");
@@ -1143,7 +1146,7 @@ static int printer_func_bind(struct usb_configuration *c,
 	return 0;
 
 fail_cdev_add:
-	device_destroy(usb_gadget_class, devt);
+	device_destroy(&usb_gadget_class, devt);
 
 fail_rx_reqs:
 	while (!list_empty(&dev->rx_reqs)) {
@@ -1410,7 +1413,7 @@ static void printer_func_unbind(struct usb_configuration *c,
 
 	dev = func_to_printer(f);
 
-	device_destroy(usb_gadget_class, MKDEV(major, dev->minor));
+	device_destroy(&usb_gadget_class, MKDEV(major, dev->minor));
 
 	/* Remove Character Device */
 	cdev_del(&dev->printer_cdev);
@@ -1512,19 +1515,14 @@ static int gprinter_setup(int count)
 	int status;
 	dev_t devt;
 
-	usb_gadget_class = class_create("usb_printer_gadget");
-	if (IS_ERR(usb_gadget_class)) {
-		status = PTR_ERR(usb_gadget_class);
-		usb_gadget_class = NULL;
-		pr_err("unable to create usb_gadget class %d\n", status);
+	status = class_register(&usb_gadget_class);
+	if (status)
 		return status;
-	}
 
 	status = alloc_chrdev_region(&devt, 0, count, "USB printer gadget");
 	if (status) {
 		pr_err("alloc_chrdev_region %d\n", status);
-		class_destroy(usb_gadget_class);
-		usb_gadget_class = NULL;
+		class_unregister(&usb_gadget_class);
 		return status;
 	}
 
@@ -1540,6 +1538,5 @@ static void gprinter_cleanup(void)
 		unregister_chrdev_region(MKDEV(major, 0), minors);
 		major = minors = 0;
 	}
-	class_destroy(usb_gadget_class);
-	usb_gadget_class = NULL;
+	class_unregister(&usb_gadget_class);
 }