Fix debugfs_create_*'s error checking method for wireless/rt2x00/

debugfs_create_*() returns NULL if an error occurs, returns -ENODEV
when debugfs is not enabled in the kernel.
Signed-off-by: NZhao Lei <zhaolei@cn.fujitsu.com>
Signed-off-by: NIvo van Doorn <IvDoorn@gmail.com>
Signed-off-by: NJohn W. Linville <linville@tuxdriver.com>

drivers/net/wireless/rt2x00/rt2x00debug.c

@@ -587,29 +587,29 @@ void rt2x00debug_register(struct rt2x00_dev *rt2x00dev)
 	intf->driver_folder =
 	    debugfs_create_dir(intf->rt2x00dev->ops->name,
 			       rt2x00dev->hw->wiphy->debugfsdir);
-	if (IS_ERR(intf->driver_folder))
+	if (IS_ERR(intf->driver_folder) || !intf->driver_folder)
 		goto exit;
 
 	intf->driver_entry =
 	    rt2x00debug_create_file_driver("driver", intf, &intf->driver_blob);
-	if (IS_ERR(intf->driver_entry))
+	if (IS_ERR(intf->driver_entry) || !intf->driver_entry)
 		goto exit;
 
 	intf->chipset_entry =
 	    rt2x00debug_create_file_chipset("chipset",
 					    intf, &intf->chipset_blob);
-	if (IS_ERR(intf->chipset_entry))
+	if (IS_ERR(intf->chipset_entry) || !intf->chipset_entry)
 		goto exit;
 
 	intf->dev_flags = debugfs_create_file("dev_flags", S_IRUSR,
 					      intf->driver_folder, intf,
 					      &rt2x00debug_fop_dev_flags);
-	if (IS_ERR(intf->dev_flags))
+	if (IS_ERR(intf->dev_flags) || !intf->dev_flags)
 		goto exit;
 
 	intf->register_folder =
 	    debugfs_create_dir("register", intf->driver_folder);
-	if (IS_ERR(intf->register_folder))
+	if (IS_ERR(intf->register_folder) || !intf->register_folder)
 		goto exit;
 
 #define RT2X00DEBUGFS_CREATE_REGISTER_ENTRY(__intf, __name)	\
@@ -619,7 +619,8 @@ void rt2x00debug_register(struct rt2x00_dev *rt2x00dev)
 			       S_IRUSR | S_IWUSR,		\
 			       (__intf)->register_folder,	\
 			       &(__intf)->offset_##__name);	\
-	if (IS_ERR((__intf)->__name##_off_entry))		\
+	if (IS_ERR((__intf)->__name##_off_entry)		\
+			|| !(__intf)->__name##_off_entry)	\
 		goto exit;					\
 								\
 	(__intf)->__name##_val_entry =				\
@@ -627,7 +628,8 @@ void rt2x00debug_register(struct rt2x00_dev *rt2x00dev)
 				S_IRUSR | S_IWUSR,		\
 				(__intf)->register_folder,	\
 				(__intf), &rt2x00debug_fop_##__name);\
-	if (IS_ERR((__intf)->__name##_val_entry))		\
+	if (IS_ERR((__intf)->__name##_val_entry)		\
+			|| !(__intf)->__name##_val_entry)	\
 		goto exit;					\
 })
 
@@ -640,13 +642,14 @@ void rt2x00debug_register(struct rt2x00_dev *rt2x00dev)
 
 	intf->queue_folder =
 	    debugfs_create_dir("queue", intf->driver_folder);
-	if (IS_ERR(intf->queue_folder))
+	if (IS_ERR(intf->queue_folder) || !intf->queue_folder)
 		goto exit;
 
 	intf->queue_frame_dump_entry =
 	    debugfs_create_file("dump", S_IRUSR, intf->queue_folder,
 				intf, &rt2x00debug_fop_queue_dump);
-	if (IS_ERR(intf->queue_frame_dump_entry))
+	if (IS_ERR(intf->queue_frame_dump_entry)
+		|| !intf->queue_frame_dump_entry)
 		goto exit;
 
 	skb_queue_head_init(&intf->frame_dump_skbqueue);