There is a helper function to create device related seq_file::
 
-   struct dentry *debugfs_create_devm_seqfile(struct device *dev,
+   void debugfs_create_devm_seqfile(struct device *dev,
                                const char *name,
                                struct dentry *parent,
                                int (*read_fn)(struct seq_file *s,
 
  *     file will be created in the root of the debugfs filesystem.
  * @read_fn: function pointer called to print the seq_file content.
  */
-struct dentry *debugfs_create_devm_seqfile(struct device *dev, const char *name,
-                                          struct dentry *parent,
-                                          int (*read_fn)(struct seq_file *s,
-                                                         void *data))
+void debugfs_create_devm_seqfile(struct device *dev, const char *name,
+                                struct dentry *parent,
+                                int (*read_fn)(struct seq_file *s, void *data))
 {
        struct debugfs_devm_entry *entry;
 
        if (IS_ERR(parent))
-               return ERR_PTR(-ENOENT);
+               return;
 
        entry = devm_kzalloc(dev, sizeof(*entry), GFP_KERNEL);
        if (!entry)
-               return ERR_PTR(-ENOMEM);
+               return;
 
        entry->read = read_fn;
        entry->dev = dev;
 
-       return debugfs_create_file(name, S_IRUGO, parent, entry,
-                                  &debugfs_devm_entry_ops);
+       debugfs_create_file(name, S_IRUGO, parent, entry,
+                           &debugfs_devm_entry_ops);
 }
 EXPORT_SYMBOL_GPL(debugfs_create_devm_seqfile);
 
                              struct dentry *parent,
                              struct debugfs_u32_array *array);
 
-struct dentry *debugfs_create_devm_seqfile(struct device *dev, const char *name,
-                                          struct dentry *parent,
-                                          int (*read_fn)(struct seq_file *s,
-                                                         void *data));
+void debugfs_create_devm_seqfile(struct device *dev, const char *name,
+                                struct dentry *parent,
+                                int (*read_fn)(struct seq_file *s, void *data));
 
 bool debugfs_initialized(void);
 
 {
 }
 
-static inline struct dentry *debugfs_create_devm_seqfile(struct device *dev,
-                                                        const char *name,
-                                                        struct dentry *parent,
-                                          int (*read_fn)(struct seq_file *s,
-                                                         void *data))
+static inline void debugfs_create_devm_seqfile(struct device *dev,
+                                              const char *name,
+                                              struct dentry *parent,
+                                              int (*read_fn)(struct seq_file *s,
+                                                             void *data))
 {
-       return ERR_PTR(-ENODEV);
 }
 
 static inline ssize_t debugfs_read_file_bool(struct file *file,