diff --git a/src/devtools/met-driver/4.9/common/interface.h b/src/devtools/met-driver/4.9/common/interface.h
new file mode 100644
index 0000000..6cbbe6d
--- /dev/null
+++ b/src/devtools/met-driver/4.9/common/interface.h
@@ -0,0 +1,78 @@
+/*
+ * Copyright (C) 2018 MediaTek Inc.
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ */
+
+#ifndef __INTERFACE_H__
+#define __INTERFACE_H__
+
+#include <linux/fs.h>
+
+#ifdef MET_USER_EVENT_SUPPORT
+extern int tag_reg(struct file_operations *const fops, struct kobject *kobj);
+extern int tag_unreg(void);
+#include "met_drv.h"
+#include "met_tag.h"
+extern struct bltable_t bltab;
+#endif
+
+extern struct metdevice met_stat;
+extern struct metdevice met_cpupmu;
+extern struct metdevice met_cookie;
+extern struct metdevice met_memstat;
+extern struct metdevice met_switch;
+extern struct metdevice met_trace_event;
+extern struct metdevice met_dummy_header;
+extern struct metdevice met_backlight;
+
+/* This variable will decide which method to access the CPU PMU counter */
+/*     0: access registers directly */
+/*     others: via Linux perf driver */
+extern unsigned int met_cpu_pmu_method;
+
+/*
+ * controls whether re-configuring pmu events after leaving cpu off state
+ */
+extern unsigned int met_cpu_pm_pmu_reconfig;
+
+extern int met_parse_num(const char *str, unsigned int *value, int len);
+extern void met_set_suspend_notify(int flag);
+
+#define	PR_CPU_NOTIFY
+#if	defined(PR_CPU_NOTIFY)
+extern int met_cpu_notify;
+#endif
+
+//#undef	MET_BOOT_MSG
+#define	MET_BOOT_MSG
+#if	defined(MET_BOOT_MSG)
+extern char met_boot_msg_tmp[256];
+extern int pr_bootmsg(int str_len, char *str);
+#define	PR_BOOTMSG(fmt, args...) { \
+	int str_len = snprintf(met_boot_msg_tmp, sizeof(met_boot_msg_tmp), \
+			       fmt, ##args); \
+	pr_bootmsg(str_len, met_boot_msg_tmp); }
+#define	PR_BOOTMSG_ONCE(fmt, args...) { \
+	static int once; \
+	if (!once) { \
+		int str_len = snprintf(met_boot_msg_tmp, \
+				       sizeof(met_boot_msg_tmp), \
+				       fmt, ##args); \
+		pr_bootmsg(str_len, met_boot_msg_tmp); \
+		once = 1; \
+	} }
+#else
+#define	pr_bootmsg(str_len, str)
+#define PR_BOOTMSG(fmt, args...)
+#define	PR_BOOTMSG_ONCE(fmt, args...)
+#endif
+
+#endif	/* __INTERFACE_H__ */