comedi: make all 'class' structures const

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

Cc: Ian Abbott <[e-mail]>
Cc: H Hartley Sweeten <[e-mail]>
Cc: Benjamin Tissoires <[e-mail]>
Cc: Ivan Orlov <[e-mail]>
Cc: Xuezhi Zhang <[e-mail]>
Suggested-by: Greg Kroah-Hartman <[e-mail]>
Signed-off-by: Ivan Orlov <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/comedi/comedi_fops.c

···
 static struct comedi_subdevice
 *comedi_subdevice_minor_table[COMEDI_NUM_SUBDEVICE_MINORS];
 
-static struct class *comedi_class;
 static struct cdev comedi_cdev;
 
 static void comedi_device_init(struct comedi_device *dev)
···
 	comedi_board_minor_table[minor] = NULL;
 	mutex_unlock(&comedi_board_minor_table_lock);
 	return dev;
-}
-
-static void comedi_free_board_dev(struct comedi_device *dev)
-{
-	if (dev) {
-		comedi_device_cleanup(dev);
-		if (dev->class_dev) {
-			device_destroy(comedi_class,
-				       MKDEV(COMEDI_MAJOR, dev->minor));
-		}
-		comedi_dev_put(dev);
-	}
 }
 
 static struct comedi_subdevice *
···
 	NULL,
 };
 ATTRIBUTE_GROUPS(comedi_dev);
+
+static const struct class comedi_class = {
+	.name = "comedi",
+	.dev_groups = comedi_dev_groups,
+};
+
+static void comedi_free_board_dev(struct comedi_device *dev)
+{
+	if (dev) {
+		comedi_device_cleanup(dev);
+		if (dev->class_dev) {
+			device_destroy(&comedi_class,
+				       MKDEV(COMEDI_MAJOR, dev->minor));
+		}
+		comedi_dev_put(dev);
+	}
+}
 
 static void __comedi_clear_subdevice_runflags(struct comedi_subdevice *s,
 					      unsigned int bits)
···
 		return ERR_PTR(-EBUSY);
 	}
 	dev->minor = i;
-	csdev = device_create(comedi_class, hardware_device,
+	csdev = device_create(&comedi_class, hardware_device,
 			      MKDEV(COMEDI_MAJOR, i), NULL, "comedi%i", i);
 	if (!IS_ERR(csdev))
 		dev->class_dev = get_device(csdev);
···
 	}
 	i += COMEDI_NUM_BOARD_MINORS;
 	s->minor = i;
-	csdev = device_create(comedi_class, dev->class_dev,
+	csdev = device_create(&comedi_class, dev->class_dev,
 			      MKDEV(COMEDI_MAJOR, i), NULL, "comedi%i_subd%i",
 			      dev->minor, s->index);
 	if (!IS_ERR(csdev))
···
 		comedi_subdevice_minor_table[i] = NULL;
 	mutex_unlock(&comedi_subdevice_minor_table_lock);
 	if (s->class_dev) {
-		device_destroy(comedi_class, MKDEV(COMEDI_MAJOR, s->minor));
+		device_destroy(&comedi_class, MKDEV(COMEDI_MAJOR, s->minor));
 		s->class_dev = NULL;
 	}
 }
···
 	if (retval)
 		goto out_unregister_chrdev_region;
 
-	comedi_class = class_create("comedi");
-	if (IS_ERR(comedi_class)) {
-		retval = PTR_ERR(comedi_class);
+	retval = class_register(&comedi_class);
+	if (retval) {
 		pr_err("failed to create class\n");
 		goto out_cdev_del;
 	}
-
-	comedi_class->dev_groups = comedi_dev_groups;
 
 	/* create devices files for legacy/manual use */
 	for (i = 0; i < comedi_num_legacy_minors; i++) {
···
 
 out_cleanup_board_minors:
 	comedi_cleanup_board_minors();
-	class_destroy(comedi_class);
+	class_unregister(&comedi_class);
 out_cdev_del:
 	cdev_del(&comedi_cdev);
 out_unregister_chrdev_region:
···
 static void __exit comedi_cleanup(void)
 {
 	comedi_cleanup_board_minors();
-	class_destroy(comedi_class);
+	class_unregister(&comedi_class);
 	cdev_del(&comedi_cdev);
 	unregister_chrdev_region(MKDEV(COMEDI_MAJOR, 0), COMEDI_NUM_MINORS);
 

drivers/comedi/drivers/comedi_test.c

···
 static bool config_mode;
 static unsigned int set_amplitude;
 static unsigned int set_period;
-static struct class *ctcls;
+static const struct class ctcls = {
+	.name = CLASS_NAME,
+};
 static struct device *ctdev;
 
 module_param_named(noauto, config_mode, bool, 0444);
···
 	}
 
 	if (!config_mode) {
-		ctcls = class_create(CLASS_NAME);
-		if (IS_ERR(ctcls)) {
+		ret = class_register(&ctcls);
+		if (ret) {
 			pr_warn("comedi_test: unable to create class\n");
 			goto clean3;
 		}
 
-		ctdev = device_create(ctcls, NULL, MKDEV(0, 0), NULL, DEV_NAME);
+		ctdev = device_create(&ctcls, NULL, MKDEV(0, 0), NULL, DEV_NAME);
 		if (IS_ERR(ctdev)) {
 			pr_warn("comedi_test: unable to create device\n");
 			goto clean2;
···
 	return 0;
 
 clean:
-	device_destroy(ctcls, MKDEV(0, 0));
+	device_destroy(&ctcls, MKDEV(0, 0));
 clean2:
-	class_destroy(ctcls);
-	ctdev = NULL;
+	class_unregister(&ctcls);
 clean3:
-	ctcls = NULL;
-
 	return 0;
 }
 module_init(comedi_test_init);
···
 	if (ctdev)
 		comedi_auto_unconfig(ctdev);
 
-	if (ctcls) {
-		device_destroy(ctcls, MKDEV(0, 0));
-		class_destroy(ctcls);
+	if (class_is_registered(&ctcls)) {
+		device_destroy(&ctcls, MKDEV(0, 0));
+		class_unregister(&ctcls);
 	}
 
 	comedi_driver_unregister(&waveform_driver);