Add error handling for class_create()

Check the return value of class_create(), unregistering the char
device and returning the error code if class creation fails.

Signed-off-by: Cheng-Yang Chou <yphbchou0911@gmail.com>

Author: EricccTaiwan

examples/chardev.c

@@ -67,6 +67,11 @@ static int __init chardev_init(void)
 #else
     cls = class_create(THIS_MODULE, DEVICE_NAME);
 #endif
+    if (IS_ERR(cls)) {
+        pr_err("Failed to create class for device\n");
+        unregister_chrdev(major, DEVICE_NAME);
+        return PTR_ERR(cls);
+    }
     device_create(cls, NULL, MKDEV(major, 0), NULL, DEVICE_NAME);
 
     pr_info("Device created on /dev/%s\n", DEVICE_NAME);

examples/chardev2.c

@@ -208,6 +208,11 @@ static int __init chardev2_init(void)
 #else
     cls = class_create(THIS_MODULE, DEVICE_FILE_NAME);
 #endif
+    if (IS_ERR(cls)) {
+        pr_err("Failed to create class for device\n");
+        unregister_chrdev(MAJOR_NUM, DEVICE_NAME);
+        return PTR_ERR(cls);
+    }
     device_create(cls, NULL, MKDEV(MAJOR_NUM, 0), NULL, DEVICE_FILE_NAME);
 
     pr_info("Device created on /dev/%s\n", DEVICE_FILE_NAME);

examples/static_key.c

@@ -63,7 +63,11 @@ static int __init chardev_init(void)
 #else
     cls = class_create(THIS_MODULE, DEVICE_NAME);
 #endif
-
+    if (IS_ERR(cls)) {
+        pr_err("Failed to create class for device\n");
+        unregister_chrdev(major, DEVICE_NAME);
+        return PTR_ERR(cls);
+    }
     device_create(cls, NULL, MKDEV(major, 0), NULL, DEVICE_NAME);
 
     pr_info("Device created on /dev/%s\n", DEVICE_NAME);