diff --git a/include/linux/hil_mlc.h b/include/linux/hil_mlc.h
new file mode 100644
index 0000000..8df29ca
--- /dev/null
+++ b/include/linux/hil_mlc.h
@@ -0,0 +1,168 @@
+/*
+ * HP Human Interface Loop Master Link Controller driver.
+ *
+ * Copyright (c) 2001 Brian S. Julin
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions, and the following disclaimer,
+ *    without modification.
+ * 2. The name of the author may not be used to endorse or promote products
+ *    derived from this software without specific prior written permission.
+ *
+ * Alternatively, this software may be distributed under the terms of the
+ * GNU General Public License ("GPL").
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE FOR
+ * ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ *
+ * References:
+ * HP-HIL Technical Reference Manual.  Hewlett Packard Product No. 45918A
+ *
+ */
+
+#include <linux/hil.h>
+#include <linux/time.h>
+#include <linux/interrupt.h>
+#include <asm/semaphore.h>
+#include <linux/serio.h>
+#include <linux/list.h>
+
+typedef struct hil_mlc hil_mlc;
+
+/* The HIL has a complicated state engine.
+ * We define the structure of nodes in the state engine here.
+ */
+enum hilse_act {
+  	/* HILSE_OUT prepares to receive input if the next node
+	 * is an IN or EXPECT, and then sends the given packet.
+	 */
+	HILSE_OUT = 0,
+
+  	/* HILSE_CTS checks if the loop is busy. */
+	HILSE_CTS,
+
+	/* HILSE_OUT_LAST sends the given command packet to 
+	 * the last configured/running device on the loop.
+	 */
+	HILSE_OUT_LAST,
+
+	/* HILSE_OUT_DISC sends the given command packet to
+	 * the next device past the last configured/running one.
+	 */
+	HILSE_OUT_DISC,
+
+	/* HILSE_FUNC runs a callback function with given arguments.
+	 * a positive return value causes the "ugly" branch to be taken.
+	 */
+	HILSE_FUNC,
+
+  	/* HILSE_IN simply expects any non-errored packet to arrive 
+	 * within arg usecs.
+	 */
+	HILSE_IN		= 0x100,
+
+  	/* HILSE_EXPECT expects a particular packet to arrive 
+	 * within arg usecs, any other packet is considered an error.
+	 */
+	HILSE_EXPECT,
+
+  	/* HILSE_EXPECT_LAST as above but dev field should be last 
+	 * discovered/operational device.
+	 */
+	HILSE_EXPECT_LAST,
+
+  	/* HILSE_EXPECT_LAST as above but dev field should be first 
+	 * undiscovered/inoperational device.
+	 */
+	HILSE_EXPECT_DISC
+};
+
+typedef int	(hilse_func) (hil_mlc *mlc, int arg);
+struct hilse_node {
+	enum hilse_act		act;	/* How to process this node         */
+	union {
+		hilse_func	*func;	/* Function to call if HILSE_FUNC   */
+		hil_packet	packet;	/* Packet to send or to compare     */
+	} object;
+	int			arg;	/* Timeout in usec or parm for func */
+	int			good;	/* Node to jump to on success       */
+	int			bad;	/* Node to jump to on error         */
+	int			ugly;	/* Node to jump to on timeout       */
+};
+
+/* Methods for back-end drivers, e.g. hp_sdc_mlc */
+typedef int	(hil_mlc_cts) (hil_mlc *mlc);
+typedef void	(hil_mlc_out) (hil_mlc *mlc);
+typedef int	(hil_mlc_in)  (hil_mlc *mlc, suseconds_t timeout);
+
+struct hil_mlc_devinfo {
+	uint8_t	idd[16];	/* Device ID Byte and Describe Record */
+	uint8_t	rsc[16];	/* Security Code Header and Record */
+	uint8_t	exd[16];	/* Extended Describe Record */
+	uint8_t	rnm[16];	/* Device name as returned by RNM command */
+};
+
+struct hil_mlc_serio_map {
+	hil_mlc *mlc;
+	int di_revmap;
+	int didx;
+};
+
+/* How many (possibly old/detached) devices the we try to keep track of */
+#define HIL_MLC_DEVMEM 16
+
+struct hil_mlc {
+	struct list_head	list;	/* hil_mlc is organized as linked list */
+
+	rwlock_t		lock;
+
+	void *priv; /* Data specific to a particular type of MLC */
+
+	int 			seidx;	/* Current node in state engine */
+	int			istarted, ostarted;
+
+	hil_mlc_cts		*cts;
+	struct semaphore	csem;   /* Raised when loop idle */
+
+	hil_mlc_out		*out;
+	struct semaphore	osem;   /* Raised when outpacket dispatched */
+	hil_packet		opacket;
+
+	hil_mlc_in		*in;
+	struct semaphore	isem;   /* Raised when a packet arrives */
+	hil_packet		ipacket[16];
+	hil_packet		imatch;
+	int			icount;
+	struct timeval		instart;
+	suseconds_t		intimeout;
+
+	int			ddi;	/* Last operational device id */
+	int			lcv;	/* LCV to throttle loops */
+	struct timeval		lcv_tv; /* Time loop was started */
+
+	int			di_map[7]; /* Maps below items to live devs */
+	struct hil_mlc_devinfo	di[HIL_MLC_DEVMEM];
+	struct serio		*serio[HIL_MLC_DEVMEM];
+	struct hil_mlc_serio_map serio_map[HIL_MLC_DEVMEM];
+	hil_packet		serio_opacket[HIL_MLC_DEVMEM];
+	int			serio_oidx[HIL_MLC_DEVMEM];
+	struct hil_mlc_devinfo	di_scratch; /* Temporary area */
+
+	int			opercnt;
+
+	struct tasklet_struct	*tasklet;
+};
+
+int hil_mlc_register(hil_mlc *mlc);
+int hil_mlc_unregister(hil_mlc *mlc);