diff --git a/Makefile b/Makefile
index f3942c44..03a0a877 100644
--- a/Makefile
+++ b/Makefile
@@ -61,6 +61,8 @@ DEAD_CODE_ELIMINATION ?= 0
 CONFIG_FSP?=1
 # Try to build without POWER8 support
 CONFIG_P8?=1
+# Try to build without PLDM code
+CONFIG_PLDM?=0
 
 #
 # Where is the source directory, must be a full path (no ~)
diff --git a/Makefile.main b/Makefile.main
index 2a346a6c..6e6f742d 100644
--- a/Makefile.main
+++ b/Makefile.main
@@ -75,7 +75,7 @@ DBG=-g
 
 CPPFLAGS := -I$(SRC)/include -Iinclude -MMD -include $(SRC)/include/config.h
 CPPFLAGS += -I$(SRC)/libfdt -I$(SRC)/libflash -I$(SRC)/libxz -I$(SRC)/libc/include -I$(SRC)
-CPPFLAGS += -I$(SRC)/libpore
+CPPFLAGS += -I$(SRC)/libpore -I$(SRC)/libmctp
 CPPFLAGS += -D__SKIBOOT__ -nostdinc
 CPPFLAGS += -isystem $(shell $(CC) -print-file-name=include)
 CPPFLAGS += -DBITS_PER_LONG=64
@@ -87,8 +87,10 @@ CPPFLAGS += -ffreestanding
 
 ifeq ($(LITTLE_ENDIAN),1)
 CPPFLAGS += -DHAVE_LITTLE_ENDIAN
+CPPFLAGS += -D__LITTLE_ENDIAN_BITFIELD
 else
 CPPFLAGS += -DHAVE_BIG_ENDIAN
+CPPFLAGS += -D__BIG_ENDIAN_BITFIELD
 endif
 
 ifeq ($(DEBUG),1)
@@ -164,6 +166,9 @@ endif
 ifeq ($(CONFIG_P8),1)
 CFLAGS += -DCONFIG_P8=1
 endif
+ifeq ($(CONFIG_PLDM),1)
+CFLAGS += -DCONFIG_PLDM=1
+endif
 
 CFLAGS += $(call try-cflag,$(CC),-Wjump-misses-init) \
 	  $(call try-cflag,$(CC),-Wsuggest-attribute=const) \
@@ -295,6 +300,9 @@ include $(SRC)/libc/Makefile.inc
 include $(SRC)/ccan/Makefile.inc
 include $(SRC)/$(DEVSRC)/Makefile.inc
 include $(SRC)/libstb/Makefile.inc
+ifeq ($(CONFIG_PLDM),1)
+include $(SRC)/libmctp/Makefile.inc
+endif
 
 # hack for travis-ci and coverity
 gard:
@@ -319,6 +327,9 @@ all: $(TARGET).lid.stb $(TARGET).lid.xz.stb
 
 OBJS := $(ASM) $(CORE) $(HW) $(PLATFORMS) $(LIBFDT) $(LIBXZ) $(LIBFLASH) $(LIBSTB)
 OBJS += $(LIBC) $(CCAN) $(DEVSRC_OBJ) $(LIBPORE)
+ifeq ($(CONFIG_PLDM),1)
+OBJS += $(LIBMCTP)
+endif
 OBJS_NO_VER = $(OBJS)
 ALL_OBJS = $(OBJS) version.o
 
diff --git a/libmctp/LICENSE b/libmctp/LICENSE
new file mode 100644
index 00000000..37fc4a76
--- /dev/null
+++ b/libmctp/LICENSE
@@ -0,0 +1,547 @@
+libmctp is released under a dual Apache-2.0 OR GPLv2+ license. The
+texts of both licences is included below.
+
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+    You should have received a copy of the GNU General Public License along
+    with this program; if not, write to the Free Software Foundation, Inc.,
+    51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+
+Also add information on how to contact you by electronic and paper mail.
+
+If the program is interactive, make it output a short notice like this
+when it starts in an interactive mode:
+
+    Gnomovision version 69, Copyright (C) year name of author
+    Gnomovision comes with ABSOLUTELY NO WARRANTY; for details type `show w'.
+    This is free software, and you are welcome to redistribute it
+    under certain conditions; type `show c' for details.
+
+The hypothetical commands `show w' and `show c' should show the appropriate
+parts of the General Public License.  Of course, the commands you use may
+be called something other than `show w' and `show c'; they could even be
+mouse-clicks or menu items--whatever suits your program.
+
+You should also get your employer (if you work as a programmer) or your
+school, if any, to sign a "copyright disclaimer" for the program, if
+necessary.  Here is a sample; alter the names:
+
+  Yoyodyne, Inc., hereby disclaims all copyright interest in the program
+  `Gnomovision' (which makes passes at compilers) written by James Hacker.
+
+  <signature of Ty Coon>, 1 April 1989
+  Ty Coon, President of Vice
+
+This General Public License does not permit incorporating your program into
+proprietary programs.  If your program is a subroutine library, you may
+consider it more useful to permit linking proprietary applications with the
+library.  If this is what you want to do, use the GNU Lesser General
+Public License instead of this License.
diff --git a/libmctp/Makefile.inc b/libmctp/Makefile.inc
new file mode 100644
index 00000000..24d6fcf5
--- /dev/null
+++ b/libmctp/Makefile.inc
@@ -0,0 +1,22 @@
+# SPDX-License-Identifier: Apache-2.0 OR GPL-2.0-or-later
+# Copyright 2022 IBM Corp.
+
+LIBMCTP_DIR ?= libmctp
+SUBDIRS += $(LIBMCTP_DIR)
+
+LIBMCTP_OBJS = crc32.o core.o alloc.o log.o
+LIBMCTP_BINDINGS ?= astlpc
+
+LIBMCTP_OBJS += $(LIBMCTP_BINDINGS:%=%.o)
+
+CFLAGS_$(LIBMCTP_DIR)/ = -I$(SRC)/ccan/endian/ \
+			-DHAVE_CONFIG_H \
+			-Wno-error \
+			-Wno-type-limits \
+			-Wno-missing-prototypes \
+			-Wno-missing-declarations \
+			-Wno-suggest-attribute=const
+
+LIBMCTP = $(LIBMCTP_DIR)/built-in.a
+
+$(LIBMCTP): $(LIBMCTP_OBJS:%=$(LIBMCTP_DIR)/%)
diff --git a/libmctp/README.skiboot b/libmctp/README.skiboot
new file mode 100644
index 00000000..cbdcb7a8
--- /dev/null
+++ b/libmctp/README.skiboot
@@ -0,0 +1,15 @@
+skiboot/libmctp/ is a minimally modified version of upstream libmctp
+that is distributed with the openbmc project hosted at
+https://github.com/openbmc/libmctp.git
+
+This version is taken from libmctp.git commit 4df106db7766d ("astlpc: Add
+mctp_astlpc_tx_done() API") by copying most
+of files from the libmctp/ directory.
+
+The only modifications from the upstream source are the additions of
+this file, Makefile.inc which has been derived from the original
+Makefile.inc, astlpc.c (compilation error when MCTP_HAVE_FILEIO is
+undefined) and the removal of several unnecessary folders and files.
+
+Local libmctp changes should be kept to a minimum, and submitted
+upstream if possible.
diff --git a/libmctp/alloc.c b/libmctp/alloc.c
new file mode 100644
index 00000000..84c3f652
--- /dev/null
+++ b/libmctp/alloc.c
@@ -0,0 +1,59 @@
+/* SPDX-License-Identifier: Apache-2.0 OR GPL-2.0-or-later */
+
+#include <assert.h>
+
+#include "libmctp.h"
+#include "libmctp-alloc.h"
+
+#ifdef HAVE_CONFIG_H
+#include "config.h"
+#endif
+
+struct {
+	void *(*m_alloc)(size_t);
+	void (*m_free)(void *);
+	void *(*m_realloc)(void *, size_t);
+} alloc_ops = {
+#ifdef MCTP_DEFAULT_ALLOC
+	malloc,
+	free,
+	realloc,
+#endif
+};
+
+/* internal-only allocation functions */
+void *__mctp_alloc(size_t size)
+{
+	if (alloc_ops.m_alloc)
+		return alloc_ops.m_alloc(size);
+	if (alloc_ops.m_realloc)
+		return alloc_ops.m_realloc(NULL, size);
+	assert(0);
+	return NULL;
+}
+
+void __mctp_free(void *ptr)
+{
+	if (alloc_ops.m_free)
+		alloc_ops.m_free(ptr);
+	else if (alloc_ops.m_realloc)
+		alloc_ops.m_realloc(ptr, 0);
+	else
+		assert(0);
+}
+
+void *__mctp_realloc(void *ptr, size_t size)
+{
+	if (alloc_ops.m_realloc)
+		return alloc_ops.m_realloc(ptr, size);
+	assert(0);
+	return NULL;
+}
+
+void mctp_set_alloc_ops(void *(*m_alloc)(size_t), void (*m_free)(void *),
+			void *(m_realloc)(void *, size_t))
+{
+	alloc_ops.m_alloc = m_alloc;
+	alloc_ops.m_free = m_free;
+	alloc_ops.m_realloc = m_realloc;
+}
diff --git a/libmctp/astlpc.c b/libmctp/astlpc.c
new file mode 100644
index 00000000..dbd1f0e2
--- /dev/null
+++ b/libmctp/astlpc.c
@@ -0,0 +1,1497 @@
+/* SPDX-License-Identifier: Apache-2.0 OR GPL-2.0-or-later */
+
+#if HAVE_CONFIG_H
+#include "config.h"
+#endif
+
+#if HAVE_ENDIAN_H
+#include <endian.h>
+#endif
+
+#include <assert.h>
+#include <errno.h>
+#include <inttypes.h>
+#include <stdbool.h>
+#include <stdlib.h>
+#include <string.h>
+
+#define pr_fmt(x) "astlpc: " x
+
+#include "container_of.h"
+#include "crc32.h"
+#include "libmctp.h"
+#include "libmctp-alloc.h"
+#include "libmctp-log.h"
+#include "libmctp-astlpc.h"
+#include "range.h"
+
+#ifdef MCTP_HAVE_FILEIO
+
+#include <unistd.h>
+#include <fcntl.h>
+#include <poll.h>
+#include <sys/ioctl.h>
+#include <sys/mman.h>
+#include <linux/aspeed-lpc-ctrl.h>
+
+/* kernel interface */
+static const char *kcs_path = "/dev/mctp0";
+static const char *lpc_path = "/dev/aspeed-lpc-ctrl";
+
+#endif
+
+enum mctp_astlpc_cmd {
+	cmd_initialise = 0x00,
+	cmd_tx_begin = 0x01,
+	cmd_rx_complete = 0x02,
+	cmd_dummy_value = 0xff,
+};
+
+enum mctp_astlpc_buffer_state {
+	/*
+	 * Prior to "Channel Ready" we mark the buffers as "idle" to catch illegal accesses. In this
+	 * state neither side is considered the owner of the buffer.
+	 *
+	 * Upon "Channel Ready", each side transitions the buffers from the initial "idle" state
+	 * to the following target states:
+	 *
+	 * Tx buffer: "acquired"
+	 * Rx buffer: "released"
+	 */
+	buffer_state_idle,
+
+	/*
+	 * Beyond initialisation by "Channel Ready", buffers are in the "acquired" state once:
+	 *
+	 * 1. We dequeue a control command transferring the buffer to our ownership out of the KCS
+	 *    interface, and
+	 * 2. We are yet to complete all of our required accesses to the buffer
+	 *
+	 * * The Tx buffer enters the "acquired" state when we dequeue the "Rx Complete" command
+	 * * The Rx buffer enters the "acquired" state when we dequeue the "Tx Begin" command
+	 *
+	 * It is a failure of implementation if it's possible for both sides to simultaneously
+	 * consider a buffer as "acquired".
+	 */
+	buffer_state_acquired,
+
+	/*
+	 * Buffers are in the "prepared" state when:
+	 *
+	 * 1. We have completed all of our required accesses (read or write) for the buffer, and
+	 * 2. We have not yet successfully enqueued the control command to hand off ownership
+	 */
+	buffer_state_prepared,
+
+	/*
+	 * Beyond initialisation by "Channel Ready", buffers are in the "released" state once:
+	 *
+	 * 1. We successfully enqueue the control command transferring ownership to the remote
+	 *    side in to the KCS interface
+	 *
+	 * * The Tx buffer enters the "released" state when we enqueue the "Tx Begin" command
+	 * * The Rx buffer enters the "released" state when we enqueue the "Rx Complete" command
+	 *
+	 * It may be the case that both sides simultaneously consider a buffer to be in the
+	 * "released" state. However, if this is true, it must also be true that a buffer ownership
+	 * transfer command has been enqueued in the KCS interface and is yet to be dequeued.
+	 */
+	buffer_state_released,
+};
+
+struct mctp_astlpc_buffer {
+	uint32_t offset;
+	uint32_t size;
+	enum mctp_astlpc_buffer_state state;
+};
+
+struct mctp_astlpc_layout {
+	struct mctp_astlpc_buffer rx;
+	struct mctp_astlpc_buffer tx;
+};
+
+struct mctp_astlpc_protocol {
+	uint16_t version;
+	uint32_t (*packet_size)(uint32_t body);
+	uint32_t (*body_size)(uint32_t packet);
+	void (*pktbuf_protect)(struct mctp_pktbuf *pkt);
+	bool (*pktbuf_validate)(struct mctp_pktbuf *pkt);
+};
+
+struct mctp_binding_astlpc {
+	struct mctp_binding binding;
+
+	void *lpc_map;
+	struct mctp_astlpc_layout layout;
+
+	uint8_t mode;
+	uint32_t requested_mtu;
+
+	const struct mctp_astlpc_protocol *proto;
+
+	/* direct ops data */
+	struct mctp_binding_astlpc_ops ops;
+	void *ops_data;
+
+	/* fileio ops data */
+	int kcs_fd;
+	uint8_t kcs_status;
+};
+
+#define binding_to_astlpc(b)                                                   \
+	container_of(b, struct mctp_binding_astlpc, binding)
+
+#define astlpc_prlog(ctx, lvl, fmt, ...)                                       \
+	do {                                                                   \
+		bool __bmc = ((ctx)->mode == MCTP_BINDING_ASTLPC_MODE_BMC);    \
+		mctp_prlog(lvl, pr_fmt("%s: " fmt), __bmc ? "bmc" : "host",    \
+			   ##__VA_ARGS__);                                     \
+	} while (0)
+
+#define astlpc_prerr(ctx, fmt, ...)                                            \
+	astlpc_prlog(ctx, MCTP_LOG_ERR, fmt, ##__VA_ARGS__)
+#define astlpc_prwarn(ctx, fmt, ...)                                           \
+	astlpc_prlog(ctx, MCTP_LOG_WARNING, fmt, ##__VA_ARGS__)
+#define astlpc_prinfo(ctx, fmt, ...)                                           \
+	astlpc_prlog(ctx, MCTP_LOG_INFO, fmt, ##__VA_ARGS__)
+#define astlpc_prdebug(ctx, fmt, ...)                                          \
+	astlpc_prlog(ctx, MCTP_LOG_DEBUG, fmt, ##__VA_ARGS__)
+
+/* clang-format off */
+#define ASTLPC_MCTP_MAGIC	0x4d435450
+#define ASTLPC_VER_BAD	0
+#define ASTLPC_VER_MIN	1
+
+/* Support testing of new binding protocols */
+#ifndef ASTLPC_VER_CUR
+#define ASTLPC_VER_CUR	3
+#endif
+/* clang-format on */
+
+#ifndef ARRAY_SIZE
+#define ARRAY_SIZE(a) (sizeof(a) / sizeof(a[0]))
+#endif
+
+static uint32_t astlpc_packet_size_v1(uint32_t body)
+{
+	assert((body + 4) > body);
+
+	return body + 4;
+}
+
+static uint32_t astlpc_body_size_v1(uint32_t packet)
+{
+	assert((packet - 4) < packet);
+
+	return packet - 4;
+}
+
+void astlpc_pktbuf_protect_v1(struct mctp_pktbuf *pkt)
+{
+	(void)pkt;
+}
+
+bool astlpc_pktbuf_validate_v1(struct mctp_pktbuf *pkt)
+{
+	(void)pkt;
+	return true;
+}
+
+static uint32_t astlpc_packet_size_v3(uint32_t body)
+{
+	assert((body + 4 + 4) > body);
+
+	return body + 4 + 4;
+}
+
+static uint32_t astlpc_body_size_v3(uint32_t packet)
+{
+	assert((packet - 4 - 4) < packet);
+
+	return packet - 4 - 4;
+}
+
+void astlpc_pktbuf_protect_v3(struct mctp_pktbuf *pkt)
+{
+	uint32_t code;
+
+	code = htobe32(crc32(mctp_pktbuf_hdr(pkt), mctp_pktbuf_size(pkt)));
+	mctp_prdebug("%s: 0x%" PRIx32, __func__, code);
+	mctp_pktbuf_push(pkt, &code, 4);
+}
+
+bool astlpc_pktbuf_validate_v3(struct mctp_pktbuf *pkt)
+{
+	uint32_t code;
+	void *check;
+
+	code = be32toh(crc32(mctp_pktbuf_hdr(pkt), mctp_pktbuf_size(pkt) - 4));
+	mctp_prdebug("%s: 0x%" PRIx32, __func__, code);
+	check = mctp_pktbuf_pop(pkt, 4);
+	return check && !memcmp(&code, check, 4);
+}
+
+static const struct mctp_astlpc_protocol astlpc_protocol_version[] = {
+	[0] = {
+		.version = 0,
+		.packet_size = NULL,
+		.body_size = NULL,
+		.pktbuf_protect = NULL,
+		.pktbuf_validate = NULL,
+	},
+	[1] = {
+		.version = 1,
+		.packet_size = astlpc_packet_size_v1,
+		.body_size = astlpc_body_size_v1,
+		.pktbuf_protect = astlpc_pktbuf_protect_v1,
+		.pktbuf_validate = astlpc_pktbuf_validate_v1,
+	},
+	[2] = {
+		.version = 2,
+		.packet_size = astlpc_packet_size_v1,
+		.body_size = astlpc_body_size_v1,
+		.pktbuf_protect = astlpc_pktbuf_protect_v1,
+		.pktbuf_validate = astlpc_pktbuf_validate_v1,
+	},
+	[3] = {
+		.version = 3,
+		.packet_size = astlpc_packet_size_v3,
+		.body_size = astlpc_body_size_v3,
+		.pktbuf_protect = astlpc_pktbuf_protect_v3,
+		.pktbuf_validate = astlpc_pktbuf_validate_v3,
+	},
+};
+
+struct mctp_lpcmap_hdr {
+	uint32_t magic;
+
+	uint16_t bmc_ver_min;
+	uint16_t bmc_ver_cur;
+	uint16_t host_ver_min;
+	uint16_t host_ver_cur;
+	uint16_t negotiated_ver;
+	uint16_t pad0;
+
+	struct {
+		uint32_t rx_offset;
+		uint32_t rx_size;
+		uint32_t tx_offset;
+		uint32_t tx_size;
+	} layout;
+} __attribute__((packed));
+
+static const uint32_t control_size = 0x100;
+
+#define LPC_WIN_SIZE (1 * 1024 * 1024)
+
+#define KCS_STATUS_BMC_READY	  0x80
+#define KCS_STATUS_CHANNEL_ACTIVE 0x40
+#define KCS_STATUS_IBF		  0x02
+#define KCS_STATUS_OBF		  0x01
+
+static inline int mctp_astlpc_kcs_write(struct mctp_binding_astlpc *astlpc,
+					enum mctp_binding_astlpc_kcs_reg reg,
+					uint8_t val)
+{
+	return astlpc->ops.kcs_write(astlpc->ops_data, reg, val);
+}
+
+static inline int mctp_astlpc_kcs_read(struct mctp_binding_astlpc *astlpc,
+				       enum mctp_binding_astlpc_kcs_reg reg,
+				       uint8_t *val)
+{
+	return astlpc->ops.kcs_read(astlpc->ops_data, reg, val);
+}
+
+static inline int mctp_astlpc_lpc_write(struct mctp_binding_astlpc *astlpc,
+					const void *buf, long offset,
+					size_t len)
+{
+	astlpc_prdebug(astlpc, "%s: %zu bytes to 0x%lx", __func__, len, offset);
+
+	assert(offset >= 0);
+
+	/* Indirect access */
+	if (astlpc->ops.lpc_write) {
+		void *data = astlpc->ops_data;
+
+		return astlpc->ops.lpc_write(data, buf, offset, len);
+	}
+
+	/* Direct mapping */
+	assert(astlpc->lpc_map);
+	memcpy(&((char *)astlpc->lpc_map)[offset], buf, len);
+
+	return 0;
+}
+
+static inline int mctp_astlpc_lpc_read(struct mctp_binding_astlpc *astlpc,
+				       void *buf, long offset, size_t len)
+{
+	astlpc_prdebug(astlpc, "%s: %zu bytes from 0x%lx", __func__, len,
+		       offset);
+
+	assert(offset >= 0);
+
+	/* Indirect access */
+	if (astlpc->ops.lpc_read) {
+		void *data = astlpc->ops_data;
+
+		return astlpc->ops.lpc_read(data, buf, offset, len);
+	}
+
+	/* Direct mapping */
+	assert(astlpc->lpc_map);
+	memcpy(buf, &((char *)astlpc->lpc_map)[offset], len);
+
+	return 0;
+}
+
+static int mctp_astlpc_kcs_set_status(struct mctp_binding_astlpc *astlpc,
+				      uint8_t status)
+{
+	uint8_t data;
+	int rc;
+
+	/* Since we're setting the status register, we want the other endpoint
+	 * to be interrupted. However, some hardware may only raise a host-side
+	 * interrupt on an ODR event.
+	 * So, write a dummy value of 0xff to ODR, which will ensure that an
+	 * interrupt is triggered, and can be ignored by the host.
+	 */
+	data = cmd_dummy_value;
+
+	rc = mctp_astlpc_kcs_write(astlpc, MCTP_ASTLPC_KCS_REG_STATUS, status);
+	if (rc) {
+		astlpc_prwarn(astlpc, "KCS status write failed");
+		return -1;
+	}
+
+	rc = mctp_astlpc_kcs_write(astlpc, MCTP_ASTLPC_KCS_REG_DATA, data);
+	if (rc) {
+		astlpc_prwarn(astlpc, "KCS dummy data write failed");
+		return -1;
+	}
+
+	return 0;
+}
+
+static int mctp_astlpc_layout_read(struct mctp_binding_astlpc *astlpc,
+				   struct mctp_astlpc_layout *layout)
+{
+	struct mctp_lpcmap_hdr hdr;
+	int rc;
+
+	rc = mctp_astlpc_lpc_read(astlpc, &hdr, 0, sizeof(hdr));
+	if (rc < 0)
+		return rc;
+
+	/* Flip the buffers as the names are defined in terms of the host */
+	if (astlpc->mode == MCTP_BINDING_ASTLPC_MODE_BMC) {
+		layout->rx.offset = be32toh(hdr.layout.tx_offset);
+		layout->rx.size = be32toh(hdr.layout.tx_size);
+		layout->tx.offset = be32toh(hdr.layout.rx_offset);
+		layout->tx.size = be32toh(hdr.layout.rx_size);
+	} else {
+		assert(astlpc->mode == MCTP_BINDING_ASTLPC_MODE_HOST);
+
+		layout->rx.offset = be32toh(hdr.layout.rx_offset);
+		layout->rx.size = be32toh(hdr.layout.rx_size);
+		layout->tx.offset = be32toh(hdr.layout.tx_offset);
+		layout->tx.size = be32toh(hdr.layout.tx_size);
+	}
+
+	return 0;
+}
+
+static int mctp_astlpc_layout_write(struct mctp_binding_astlpc *astlpc,
+				    struct mctp_astlpc_layout *layout)
+{
+	uint32_t rx_size_be;
+
+	if (astlpc->mode == MCTP_BINDING_ASTLPC_MODE_BMC) {
+		struct mctp_lpcmap_hdr hdr;
+
+		/*
+		 * Flip the buffers as the names are defined in terms of the
+		 * host
+		 */
+		hdr.layout.rx_offset = htobe32(layout->tx.offset);
+		hdr.layout.rx_size = htobe32(layout->tx.size);
+		hdr.layout.tx_offset = htobe32(layout->rx.offset);
+		hdr.layout.tx_size = htobe32(layout->rx.size);
+
+		return mctp_astlpc_lpc_write(astlpc, &hdr.layout,
+					     offsetof(struct mctp_lpcmap_hdr,
+						      layout),
+					     sizeof(hdr.layout));
+	}
+
+	assert(astlpc->mode == MCTP_BINDING_ASTLPC_MODE_HOST);
+
+	/*
+	 * As of v2 we only need to write rx_size - the offsets are controlled
+	 * by the BMC, as is the BMC's rx_size (host tx_size).
+	 */
+	rx_size_be = htobe32(layout->rx.size);
+	return mctp_astlpc_lpc_write(astlpc, &rx_size_be,
+				     offsetof(struct mctp_lpcmap_hdr,
+					      layout.rx_size),
+				     sizeof(rx_size_be));
+}
+
+static bool
+mctp_astlpc_buffer_validate(const struct mctp_binding_astlpc *astlpc,
+			    const struct mctp_astlpc_buffer *buf,
+			    const char *name)
+{
+	/* Check for overflow */
+	if (buf->offset + buf->size < buf->offset) {
+		mctp_prerr(
+			"%s packet buffer parameters overflow: offset: 0x%" PRIx32
+			", size: %" PRIu32,
+			name, buf->offset, buf->size);
+		return false;
+	}
+
+	/* Check that the buffers are contained within the allocated space */
+	if (buf->offset + buf->size > LPC_WIN_SIZE) {
+		mctp_prerr(
+			"%s packet buffer parameters exceed %uM window size: offset: 0x%" PRIx32
+			", size: %" PRIu32,
+			name, (LPC_WIN_SIZE / (1024 * 1024)), buf->offset,
+			buf->size);
+		return false;
+	}
+
+	/* Check that the baseline transmission unit is supported */
+	if (buf->size <
+	    astlpc->proto->packet_size(MCTP_PACKET_SIZE(MCTP_BTU))) {
+		mctp_prerr(
+			"%s packet buffer too small: Require %" PRIu32
+			" bytes to support the %u byte baseline transmission unit, found %" PRIu32,
+			name,
+			astlpc->proto->packet_size(MCTP_PACKET_SIZE(MCTP_BTU)),
+			MCTP_BTU, buf->size);
+		return false;
+	}
+
+	/* Check for overlap with the control space */
+	if (buf->offset < control_size) {
+		mctp_prerr(
+			"%s packet buffer overlaps control region {0x%" PRIx32
+			", %" PRIu32 "}: Rx {0x%" PRIx32 ", %" PRIu32 "}",
+			name, 0U, control_size, buf->offset, buf->size);
+		return false;
+	}
+
+	return true;
+}
+
+static bool
+mctp_astlpc_layout_validate(const struct mctp_binding_astlpc *astlpc,
+			    const struct mctp_astlpc_layout *layout)
+{
+	const struct mctp_astlpc_buffer *rx = &layout->rx;
+	const struct mctp_astlpc_buffer *tx = &layout->tx;
+	bool rx_valid, tx_valid;
+
+	rx_valid = mctp_astlpc_buffer_validate(astlpc, rx, "Rx");
+	tx_valid = mctp_astlpc_buffer_validate(astlpc, tx, "Tx");
+
+	if (!(rx_valid && tx_valid))
+		return false;
+
+	/* Check that the buffers are disjoint */
+	if ((rx->offset <= tx->offset && rx->offset + rx->size > tx->offset) ||
+	    (tx->offset <= rx->offset && tx->offset + tx->size > rx->offset)) {
+		mctp_prerr("Rx and Tx packet buffers overlap: Rx {0x%" PRIx32
+			   ", %" PRIu32 "}, Tx {0x%" PRIx32 ", %" PRIu32 "}",
+			   rx->offset, rx->size, tx->offset, tx->size);
+		return false;
+	}
+
+	return true;
+}
+
+static int mctp_astlpc_init_bmc(struct mctp_binding_astlpc *astlpc)
+{
+	struct mctp_lpcmap_hdr hdr = { 0 };
+	uint8_t status;
+	uint32_t sz;
+
+	/*
+	 * The largest buffer size is half of the allocated MCTP space
+	 * excluding the control space.
+	 */
+	sz = ((LPC_WIN_SIZE - control_size) / 2);
+
+	/*
+	 * Trim the MTU to a multiple of 16 to meet the requirements of 12.17
+	 * Query Hop in DSP0236 v1.3.0.
+	 */
+	sz = MCTP_BODY_SIZE(astlpc->proto->body_size(sz));
+	sz &= ~0xfUL;
+	sz = astlpc->proto->packet_size(MCTP_PACKET_SIZE(sz));
+
+	if (astlpc->requested_mtu) {
+		uint32_t rpkt, rmtu;
+
+		rmtu = astlpc->requested_mtu;
+		rpkt = astlpc->proto->packet_size(MCTP_PACKET_SIZE(rmtu));
+		sz = MIN(sz, rpkt);
+	}
+
+	/* Flip the buffers as the names are defined in terms of the host */
+	astlpc->layout.tx.offset = control_size;
+	astlpc->layout.tx.size = sz;
+	astlpc->layout.rx.offset =
+		astlpc->layout.tx.offset + astlpc->layout.tx.size;
+	astlpc->layout.rx.size = sz;
+
+	if (!mctp_astlpc_layout_validate(astlpc, &astlpc->layout)) {
+		astlpc_prerr(astlpc, "Cannot support an MTU of %" PRIu32, sz);
+		return -EINVAL;
+	}
+
+	hdr = (struct mctp_lpcmap_hdr){
+		.magic = htobe32(ASTLPC_MCTP_MAGIC),
+		.bmc_ver_min = htobe16(ASTLPC_VER_MIN),
+		.bmc_ver_cur = htobe16(ASTLPC_VER_CUR),
+
+		/* Flip the buffers back as we're now describing the host's
+		 * configuration to the host */
+		.layout.rx_offset = htobe32(astlpc->layout.tx.offset),
+		.layout.rx_size = htobe32(astlpc->layout.tx.size),
+		.layout.tx_offset = htobe32(astlpc->layout.rx.offset),
+		.layout.tx_size = htobe32(astlpc->layout.rx.size),
+	};
+
+	mctp_astlpc_lpc_write(astlpc, &hdr, 0, sizeof(hdr));
+
+	/*
+	 * Set status indicating that the BMC is now active. Be explicit about
+	 * clearing OBF; we're reinitialising the binding and so any previous
+	 * buffer state is irrelevant.
+	 */
+	status = KCS_STATUS_BMC_READY & ~KCS_STATUS_OBF;
+	return mctp_astlpc_kcs_set_status(astlpc, status);
+}
+
+static int mctp_binding_astlpc_start_bmc(struct mctp_binding *b)
+{
+	struct mctp_binding_astlpc *astlpc =
+		container_of(b, struct mctp_binding_astlpc, binding);
+
+	astlpc->proto = &astlpc_protocol_version[ASTLPC_VER_CUR];
+
+	return mctp_astlpc_init_bmc(astlpc);
+}
+
+static bool mctp_astlpc_validate_version(uint16_t bmc_ver_min,
+					 uint16_t bmc_ver_cur,
+					 uint16_t host_ver_min,
+					 uint16_t host_ver_cur)
+{
+	if (!(bmc_ver_min && bmc_ver_cur && host_ver_min && host_ver_cur)) {
+		mctp_prerr("Invalid version present in [%" PRIu16 ", %" PRIu16
+			   "], [%" PRIu16 ", %" PRIu16 "]",
+			   bmc_ver_min, bmc_ver_cur, host_ver_min,
+			   host_ver_cur);
+		return false;
+	} else if (bmc_ver_min > bmc_ver_cur) {
+		mctp_prerr("Invalid bmc version range [%" PRIu16 ", %" PRIu16
+			   "]",
+			   bmc_ver_min, bmc_ver_cur);
+		return false;
+	} else if (host_ver_min > host_ver_cur) {
+		mctp_prerr("Invalid host version range [%" PRIu16 ", %" PRIu16
+			   "]",
+			   host_ver_min, host_ver_cur);
+		return false;
+	} else if ((host_ver_cur < bmc_ver_min) ||
+		   (host_ver_min > bmc_ver_cur)) {
+		mctp_prerr(
+			"Unable to satisfy version negotiation with ranges [%" PRIu16
+			", %" PRIu16 "] and [%" PRIu16 ", %" PRIu16 "]",
+			bmc_ver_min, bmc_ver_cur, host_ver_min, host_ver_cur);
+		return false;
+	}
+
+	return true;
+}
+
+static int mctp_astlpc_negotiate_layout_host(struct mctp_binding_astlpc *astlpc)
+{
+	struct mctp_astlpc_layout layout;
+	uint32_t rmtu;
+	uint32_t sz;
+	int rc;
+
+	rc = mctp_astlpc_layout_read(astlpc, &layout);
+	if (rc < 0)
+		return rc;
+
+	if (!mctp_astlpc_layout_validate(astlpc, &layout)) {
+		astlpc_prerr(
+			astlpc,
+			"BMC provided invalid buffer layout: Rx {0x%" PRIx32
+			", %" PRIu32 "}, Tx {0x%" PRIx32 ", %" PRIu32 "}",
+			layout.rx.offset, layout.rx.size, layout.tx.offset,
+			layout.tx.size);
+		return -EINVAL;
+	}
+
+	astlpc_prinfo(astlpc, "Desire an MTU of %" PRIu32 " bytes",
+		      astlpc->requested_mtu);
+
+	rmtu = astlpc->requested_mtu;
+	sz = astlpc->proto->packet_size(MCTP_PACKET_SIZE(rmtu));
+	layout.rx.size = sz;
+
+	if (!mctp_astlpc_layout_validate(astlpc, &layout)) {
+		astlpc_prerr(
+			astlpc,
+			"Generated invalid buffer layout with size %" PRIu32
+			": Rx {0x%" PRIx32 ", %" PRIu32 "}, Tx {0x%" PRIx32
+			", %" PRIu32 "}",
+			sz, layout.rx.offset, layout.rx.size, layout.tx.offset,
+			layout.tx.size);
+		return -EINVAL;
+	}
+
+	astlpc_prinfo(astlpc, "Requesting MTU of %" PRIu32 " bytes",
+		      astlpc->requested_mtu);
+
+	return mctp_astlpc_layout_write(astlpc, &layout);
+}
+
+static uint16_t mctp_astlpc_negotiate_version(uint16_t bmc_ver_min,
+					      uint16_t bmc_ver_cur,
+					      uint16_t host_ver_min,
+					      uint16_t host_ver_cur)
+{
+	if (!mctp_astlpc_validate_version(bmc_ver_min, bmc_ver_cur,
+					  host_ver_min, host_ver_cur))
+		return ASTLPC_VER_BAD;
+
+	if (bmc_ver_cur < host_ver_cur)
+		return bmc_ver_cur;
+
+	return host_ver_cur;
+}
+
+static int mctp_astlpc_init_host(struct mctp_binding_astlpc *astlpc)
+{
+	const uint16_t ver_min_be = htobe16(ASTLPC_VER_MIN);
+	const uint16_t ver_cur_be = htobe16(ASTLPC_VER_CUR);
+	uint16_t bmc_ver_min, bmc_ver_cur, negotiated;
+	struct mctp_lpcmap_hdr hdr;
+	uint8_t status;
+	int rc;
+
+	rc = mctp_astlpc_kcs_read(astlpc, MCTP_ASTLPC_KCS_REG_STATUS, &status);
+	if (rc) {
+		mctp_prwarn("KCS status read failed");
+		return rc;
+	}
+
+	astlpc->kcs_status = status;
+
+	if (!(status & KCS_STATUS_BMC_READY))
+		return -EHOSTDOWN;
+
+	mctp_astlpc_lpc_read(astlpc, &hdr, 0, sizeof(hdr));
+
+	bmc_ver_min = be16toh(hdr.bmc_ver_min);
+	bmc_ver_cur = be16toh(hdr.bmc_ver_cur);
+
+	/* Calculate the expected value of negotiated_ver */
+	negotiated = mctp_astlpc_negotiate_version(
+		bmc_ver_min, bmc_ver_cur, ASTLPC_VER_MIN, ASTLPC_VER_CUR);
+	if (!negotiated) {
+		astlpc_prerr(astlpc, "Cannot negotiate with invalid versions");
+		return -EINVAL;
+	}
+
+	/* Assign protocol ops so we can calculate the packet buffer sizes */
+	assert(negotiated < ARRAY_SIZE(astlpc_protocol_version));
+	astlpc->proto = &astlpc_protocol_version[negotiated];
+
+	/* Negotiate packet buffers in v2 style if the BMC supports it */
+	if (negotiated >= 2) {
+		rc = mctp_astlpc_negotiate_layout_host(astlpc);
+		if (rc < 0)
+			return rc;
+	}
+
+	/* Advertise the host's supported protocol versions */
+	mctp_astlpc_lpc_write(astlpc, &ver_min_be,
+			      offsetof(struct mctp_lpcmap_hdr, host_ver_min),
+			      sizeof(ver_min_be));
+
+	mctp_astlpc_lpc_write(astlpc, &ver_cur_be,
+			      offsetof(struct mctp_lpcmap_hdr, host_ver_cur),
+			      sizeof(ver_cur_be));
+
+	/* Send channel init command */
+	rc = mctp_astlpc_kcs_write(astlpc, MCTP_ASTLPC_KCS_REG_DATA, 0x0);
+	if (rc) {
+		astlpc_prwarn(astlpc, "KCS write failed");
+	}
+
+	/*
+	 * Configure the host so `astlpc->proto->version == 0` holds until we
+	 * receive a subsequent status update from the BMC. Until then,
+	 * `astlpc->proto->version == 0` indicates that we're yet to complete
+	 * the channel initialisation handshake.
+	 *
+	 * When the BMC provides a status update with KCS_STATUS_CHANNEL_ACTIVE
+	 * set we will assign the appropriate protocol ops struct in accordance
+	 * with `negotiated_ver`.
+	 */
+	astlpc->proto = &astlpc_protocol_version[ASTLPC_VER_BAD];
+
+	return rc;
+}
+
+static int mctp_binding_astlpc_start_host(struct mctp_binding *b)
+{
+	struct mctp_binding_astlpc *astlpc =
+		container_of(b, struct mctp_binding_astlpc, binding);
+
+	return mctp_astlpc_init_host(astlpc);
+}
+
+static bool __mctp_astlpc_kcs_ready(struct mctp_binding_astlpc *astlpc,
+				    uint8_t status, bool is_write)
+{
+	bool is_bmc;
+	bool ready_state;
+	uint8_t flag;
+
+	is_bmc = (astlpc->mode == MCTP_BINDING_ASTLPC_MODE_BMC);
+	flag = (is_bmc ^ is_write) ? KCS_STATUS_IBF : KCS_STATUS_OBF;
+	ready_state = is_write ? 0 : 1;
+
+	return !!(status & flag) == ready_state;
+}
+
+static inline bool
+mctp_astlpc_kcs_read_ready(struct mctp_binding_astlpc *astlpc, uint8_t status)
+{
+	return __mctp_astlpc_kcs_ready(astlpc, status, false);
+}
+
+static inline bool
+mctp_astlpc_kcs_write_ready(struct mctp_binding_astlpc *astlpc, uint8_t status)
+{
+	return __mctp_astlpc_kcs_ready(astlpc, status, true);
+}
+
+static int mctp_astlpc_kcs_send(struct mctp_binding_astlpc *astlpc,
+				enum mctp_astlpc_cmd data)
+{
+	uint8_t status;
+	int rc;
+
+	rc = mctp_astlpc_kcs_read(astlpc, MCTP_ASTLPC_KCS_REG_STATUS, &status);
+	if (rc) {
+		astlpc_prwarn(astlpc, "KCS status read failed");
+		return -EIO;
+	}
+	if (!mctp_astlpc_kcs_write_ready(astlpc, status))
+		return -EBUSY;
+
+	rc = mctp_astlpc_kcs_write(astlpc, MCTP_ASTLPC_KCS_REG_DATA, data);
+	if (rc) {
+		astlpc_prwarn(astlpc, "KCS data write failed");
+		return -EIO;
+	}
+
+	return 0;
+}
+
+static int mctp_binding_astlpc_tx(struct mctp_binding *b,
+				  struct mctp_pktbuf *pkt)
+{
+	struct mctp_binding_astlpc *astlpc = binding_to_astlpc(b);
+	uint32_t len, len_be;
+	struct mctp_hdr *hdr;
+	int rc;
+
+	hdr = mctp_pktbuf_hdr(pkt);
+	len = mctp_pktbuf_size(pkt);
+
+	astlpc_prdebug(astlpc,
+		       "%s: Transmitting %" PRIu32
+		       "-byte packet (%hhu, %hhu, 0x%hhx)",
+		       __func__, len, hdr->src, hdr->dest, hdr->flags_seq_tag);
+
+	if (len > astlpc->proto->body_size(astlpc->layout.tx.size)) {
+		astlpc_prwarn(astlpc, "invalid TX len %" PRIu32 ": %" PRIu32,
+			      len,
+			      astlpc->proto->body_size(astlpc->layout.tx.size));
+		return -EMSGSIZE;
+	}
+
+	mctp_binding_set_tx_enabled(b, false);
+
+	len_be = htobe32(len);
+	mctp_astlpc_lpc_write(astlpc, &len_be, astlpc->layout.tx.offset,
+			      sizeof(len_be));
+
+	astlpc->proto->pktbuf_protect(pkt);
+	len = mctp_pktbuf_size(pkt);
+
+	mctp_astlpc_lpc_write(astlpc, hdr, astlpc->layout.tx.offset + 4, len);
+
+	astlpc->layout.tx.state = buffer_state_prepared;
+
+	rc = mctp_astlpc_kcs_send(astlpc, cmd_tx_begin);
+	if (!rc)
+		astlpc->layout.tx.state = buffer_state_released;
+
+	return rc == -EBUSY ? 0 : rc;
+}
+
+static uint32_t mctp_astlpc_calculate_mtu(struct mctp_binding_astlpc *astlpc,
+					  struct mctp_astlpc_layout *layout)
+{
+	uint32_t low, high, limit, rpkt;
+
+	/* Derive the largest MTU the BMC _can_ support */
+	low = MIN(astlpc->layout.rx.offset, astlpc->layout.tx.offset);
+	high = MAX(astlpc->layout.rx.offset, astlpc->layout.tx.offset);
+	limit = high - low;
+
+	/* Determine the largest MTU the BMC _wants_ to support */
+	if (astlpc->requested_mtu) {
+		uint32_t rmtu = astlpc->requested_mtu;
+
+		rpkt = astlpc->proto->packet_size(MCTP_PACKET_SIZE(rmtu));
+		limit = MIN(limit, rpkt);
+	}
+
+	/* Determine the accepted MTU, applied both directions by convention */
+	rpkt = MIN(limit, layout->tx.size);
+	return MCTP_BODY_SIZE(astlpc->proto->body_size(rpkt));
+}
+
+static int mctp_astlpc_negotiate_layout_bmc(struct mctp_binding_astlpc *astlpc)
+{
+	struct mctp_astlpc_layout proposed, pending;
+	uint32_t sz, mtu;
+	int rc;
+
+	/* Do we have a valid protocol version? */
+	if (!astlpc->proto->version)
+		return -EINVAL;
+
+	/* Extract the host's proposed layout */
+	rc = mctp_astlpc_layout_read(astlpc, &proposed);
+	if (rc < 0)
+		return rc;
+
+	/* Do we have a reasonable layout? */
+	if (!mctp_astlpc_layout_validate(astlpc, &proposed))
+		return -EINVAL;
+
+	/* Negotiate the MTU */
+	mtu = mctp_astlpc_calculate_mtu(astlpc, &proposed);
+	sz = astlpc->proto->packet_size(MCTP_PACKET_SIZE(mtu));
+
+	/*
+	 * Use symmetric MTUs by convention and to pass constraints in rx/tx
+	 * functions
+	 */
+	pending = astlpc->layout;
+	pending.tx.size = sz;
+	pending.rx.size = sz;
+
+	if (mctp_astlpc_layout_validate(astlpc, &pending)) {
+		/* We found a sensible Rx MTU, so honour it */
+		astlpc->layout = pending;
+
+		/* Enforce the negotiated MTU */
+		rc = mctp_astlpc_layout_write(astlpc, &astlpc->layout);
+		if (rc < 0)
+			return rc;
+
+		astlpc_prinfo(astlpc, "Negotiated an MTU of %" PRIu32 " bytes",
+			      mtu);
+	} else {
+		astlpc_prwarn(astlpc, "MTU negotiation failed");
+		return -EINVAL;
+	}
+
+	if (astlpc->proto->version >= 2)
+		astlpc->binding.pkt_size = MCTP_PACKET_SIZE(mtu);
+
+	return 0;
+}
+
+static void mctp_astlpc_init_channel(struct mctp_binding_astlpc *astlpc)
+{
+	uint16_t negotiated, negotiated_be;
+	struct mctp_lpcmap_hdr hdr;
+	uint8_t status;
+	int rc;
+
+	mctp_astlpc_lpc_read(astlpc, &hdr, 0, sizeof(hdr));
+
+	/* Version negotiation */
+	negotiated = mctp_astlpc_negotiate_version(ASTLPC_VER_MIN,
+						   ASTLPC_VER_CUR,
+						   be16toh(hdr.host_ver_min),
+						   be16toh(hdr.host_ver_cur));
+
+	/* MTU negotiation requires knowing which protocol we'll use */
+	assert(negotiated < ARRAY_SIZE(astlpc_protocol_version));
+	astlpc->proto = &astlpc_protocol_version[negotiated];
+
+	/* Host Rx MTU negotiation: Failure terminates channel init */
+	rc = mctp_astlpc_negotiate_layout_bmc(astlpc);
+	if (rc < 0)
+		negotiated = ASTLPC_VER_BAD;
+
+	/* Populate the negotiated version */
+	negotiated_be = htobe16(negotiated);
+	mctp_astlpc_lpc_write(astlpc, &negotiated_be,
+			      offsetof(struct mctp_lpcmap_hdr, negotiated_ver),
+			      sizeof(negotiated_be));
+
+	/* Track buffer ownership */
+	astlpc->layout.tx.state = buffer_state_acquired;
+	astlpc->layout.rx.state = buffer_state_released;
+
+	/* Finalise the configuration */
+	status = KCS_STATUS_BMC_READY | KCS_STATUS_OBF;
+	if (negotiated > 0) {
+		astlpc_prinfo(astlpc, "Negotiated binding version %" PRIu16,
+			      negotiated);
+		status |= KCS_STATUS_CHANNEL_ACTIVE;
+	} else {
+		astlpc_prerr(astlpc, "Failed to initialise channel");
+	}
+
+	mctp_astlpc_kcs_set_status(astlpc, status);
+
+	mctp_binding_set_tx_enabled(&astlpc->binding,
+				    status & KCS_STATUS_CHANNEL_ACTIVE);
+}
+
+static void mctp_astlpc_rx_start(struct mctp_binding_astlpc *astlpc)
+{
+	struct mctp_pktbuf *pkt;
+	struct mctp_hdr *hdr;
+	uint32_t body, packet;
+
+	mctp_astlpc_lpc_read(astlpc, &body, astlpc->layout.rx.offset,
+			     sizeof(body));
+	body = be32toh(body);
+
+	if (body > astlpc->proto->body_size(astlpc->layout.rx.size)) {
+		astlpc_prwarn(astlpc, "invalid RX len 0x%x", body);
+		return;
+	}
+
+	if ((size_t)body > astlpc->binding.pkt_size) {
+		astlpc_prwarn(astlpc, "invalid RX len 0x%x", body);
+		return;
+	}
+
+	/* Eliminate the medium-specific header that we just read */
+	packet = astlpc->proto->packet_size(body) - 4;
+	pkt = mctp_pktbuf_alloc(&astlpc->binding, packet);
+	if (!pkt) {
+		astlpc_prwarn(astlpc, "unable to allocate pktbuf len 0x%x",
+			      packet);
+		return;
+	}
+
+	/*
+	 * Read payload and medium-specific trailer from immediately after the
+	 * medium-specific header.
+	 */
+	mctp_astlpc_lpc_read(astlpc, mctp_pktbuf_hdr(pkt),
+			     astlpc->layout.rx.offset + 4, packet);
+
+	astlpc->layout.rx.state = buffer_state_prepared;
+
+	/* Inform the other side of the MCTP interface that we have read
+	 * the packet off the bus before handling the contents of the packet.
+	 */
+	if (!mctp_astlpc_kcs_send(astlpc, cmd_rx_complete))
+		astlpc->layout.rx.state = buffer_state_released;
+
+	hdr = mctp_pktbuf_hdr(pkt);
+	if (hdr->ver != 1) {
+		mctp_pktbuf_free(pkt);
+		astlpc_prdebug(astlpc, "Dropped packet with invalid version");
+		return;
+	}
+
+	/*
+	 * v3 will validate the CRC32 in the medium-specific trailer and adjust
+	 * the packet size accordingly. On older protocols validation is a no-op
+	 * that always returns true.
+	 */
+	if (astlpc->proto->pktbuf_validate(pkt)) {
+		mctp_bus_rx(&astlpc->binding, pkt);
+	} else {
+		/* TODO: Drop any associated assembly */
+		mctp_pktbuf_free(pkt);
+		astlpc_prdebug(astlpc, "Dropped corrupt packet");
+	}
+}
+
+static void mctp_astlpc_tx_complete(struct mctp_binding_astlpc *astlpc)
+{
+	astlpc->layout.tx.state = buffer_state_acquired;
+	mctp_binding_set_tx_enabled(&astlpc->binding, true);
+}
+
+static int mctp_astlpc_finalise_channel(struct mctp_binding_astlpc *astlpc)
+{
+	struct mctp_astlpc_layout layout;
+	uint16_t negotiated;
+	int rc;
+
+	rc = mctp_astlpc_lpc_read(astlpc, &negotiated,
+				  offsetof(struct mctp_lpcmap_hdr,
+					   negotiated_ver),
+				  sizeof(negotiated));
+	if (rc < 0)
+		return rc;
+
+	negotiated = be16toh(negotiated);
+	astlpc_prerr(astlpc, "Version negotiation got: %u", negotiated);
+
+	if (negotiated == ASTLPC_VER_BAD || negotiated < ASTLPC_VER_MIN ||
+	    negotiated > ASTLPC_VER_CUR) {
+		astlpc_prerr(astlpc, "Failed to negotiate version, got: %u\n",
+			     negotiated);
+		return -EINVAL;
+	}
+
+	assert(negotiated < ARRAY_SIZE(astlpc_protocol_version));
+	astlpc->proto = &astlpc_protocol_version[negotiated];
+
+	rc = mctp_astlpc_layout_read(astlpc, &layout);
+	if (rc < 0)
+		return rc;
+
+	if (!mctp_astlpc_layout_validate(astlpc, &layout)) {
+		mctp_prerr("BMC proposed invalid buffer parameters");
+		return -EINVAL;
+	}
+
+	astlpc->layout = layout;
+
+	if (negotiated >= 2)
+		astlpc->binding.pkt_size =
+			astlpc->proto->body_size(astlpc->layout.tx.size);
+
+	/* Track buffer ownership */
+	astlpc->layout.tx.state = buffer_state_acquired;
+	astlpc->layout.rx.state = buffer_state_released;
+
+	return 0;
+}
+
+static int mctp_astlpc_update_channel(struct mctp_binding_astlpc *astlpc,
+				      uint8_t status)
+{
+	uint8_t updated;
+	int rc = 0;
+
+	assert(astlpc->mode == MCTP_BINDING_ASTLPC_MODE_HOST);
+
+	updated = astlpc->kcs_status ^ status;
+
+	astlpc_prdebug(astlpc, "%s: status: 0x%x, update: 0x%x", __func__,
+		       status, updated);
+
+	if (updated & KCS_STATUS_BMC_READY) {
+		if (status & KCS_STATUS_BMC_READY) {
+			astlpc->kcs_status = status;
+			return astlpc->binding.start(&astlpc->binding);
+		} else {
+			/* Shut down the channel */
+			astlpc->layout.rx.state = buffer_state_idle;
+			astlpc->layout.tx.state = buffer_state_idle;
+			mctp_binding_set_tx_enabled(&astlpc->binding, false);
+		}
+	}
+
+	if (astlpc->proto->version == 0 ||
+	    updated & KCS_STATUS_CHANNEL_ACTIVE) {
+		bool enable;
+
+		astlpc->layout.rx.state = buffer_state_idle;
+		astlpc->layout.tx.state = buffer_state_idle;
+		rc = mctp_astlpc_finalise_channel(astlpc);
+		enable = (status & KCS_STATUS_CHANNEL_ACTIVE) && rc == 0;
+		mctp_binding_set_tx_enabled(&astlpc->binding, enable);
+	}
+
+	astlpc->kcs_status = status;
+
+	return rc;
+}
+
+bool mctp_astlpc_tx_done(struct mctp_binding_astlpc *astlpc)
+{
+	return astlpc->layout.tx.state == buffer_state_acquired;
+}
+
+int mctp_astlpc_poll(struct mctp_binding_astlpc *astlpc)
+{
+	uint8_t status, data;
+	int rc;
+
+	if (astlpc->layout.rx.state == buffer_state_prepared)
+		if (!mctp_astlpc_kcs_send(astlpc, cmd_rx_complete))
+			astlpc->layout.rx.state = buffer_state_released;
+
+	if (astlpc->layout.tx.state == buffer_state_prepared)
+		if (!mctp_astlpc_kcs_send(astlpc, cmd_tx_begin))
+			astlpc->layout.tx.state = buffer_state_released;
+
+	rc = mctp_astlpc_kcs_read(astlpc, MCTP_ASTLPC_KCS_REG_STATUS, &status);
+	if (rc) {
+		astlpc_prwarn(astlpc, "KCS read error");
+		return -1;
+	}
+
+	astlpc_prdebug(astlpc, "%s: status: 0x%hhx", __func__, status);
+
+	if (!mctp_astlpc_kcs_read_ready(astlpc, status))
+		return 0;
+
+	rc = mctp_astlpc_kcs_read(astlpc, MCTP_ASTLPC_KCS_REG_DATA, &data);
+	if (rc) {
+		astlpc_prwarn(astlpc, "KCS data read error");
+		return -1;
+	}
+
+	astlpc_prdebug(astlpc, "%s: data: 0x%hhx", __func__, data);
+
+	if (!astlpc->proto->version &&
+	    !(data == cmd_initialise || data == cmd_dummy_value)) {
+		astlpc_prwarn(astlpc, "Invalid message for binding state: 0x%x",
+			      data);
+		return 0;
+	}
+
+	switch (data) {
+	case cmd_initialise:
+		mctp_astlpc_init_channel(astlpc);
+		break;
+	case cmd_tx_begin:
+		if (astlpc->layout.rx.state != buffer_state_released) {
+			astlpc_prerr(
+				astlpc,
+				"Protocol error: Invalid Rx buffer state for event %d: %d\n",
+				data, astlpc->layout.rx.state);
+			return 0;
+		}
+		mctp_astlpc_rx_start(astlpc);
+		break;
+	case cmd_rx_complete:
+		if (astlpc->layout.tx.state != buffer_state_released) {
+			astlpc_prerr(
+				astlpc,
+				"Protocol error: Invalid Tx buffer state for event %d: %d\n",
+				data, astlpc->layout.tx.state);
+			return 0;
+		}
+		mctp_astlpc_tx_complete(astlpc);
+		break;
+	case cmd_dummy_value:
+		/* No responsibilities for the BMC on 0xff */
+		if (astlpc->mode == MCTP_BINDING_ASTLPC_MODE_HOST) {
+			rc = mctp_astlpc_update_channel(astlpc, status);
+			if (rc < 0)
+				return rc;
+		}
+		break;
+	default:
+		astlpc_prwarn(astlpc, "unknown message 0x%x", data);
+	}
+
+	/* Handle silent loss of bmc-ready */
+	if (astlpc->mode == MCTP_BINDING_ASTLPC_MODE_HOST) {
+		if (!(status & KCS_STATUS_BMC_READY && data == cmd_dummy_value))
+			return mctp_astlpc_update_channel(astlpc, status);
+	}
+
+	return rc;
+}
+
+/* allocate and basic initialisation */
+static struct mctp_binding_astlpc *__mctp_astlpc_init(uint8_t mode,
+						      uint32_t mtu)
+{
+	struct mctp_binding_astlpc *astlpc;
+
+	assert((mode == MCTP_BINDING_ASTLPC_MODE_BMC) ||
+	       (mode == MCTP_BINDING_ASTLPC_MODE_HOST));
+
+	astlpc = __mctp_alloc(sizeof(*astlpc));
+	if (!astlpc)
+		return NULL;
+
+	memset(astlpc, 0, sizeof(*astlpc));
+	astlpc->mode = mode;
+	astlpc->lpc_map = NULL;
+	astlpc->layout.rx.state = buffer_state_idle;
+	astlpc->layout.tx.state = buffer_state_idle;
+	astlpc->requested_mtu = mtu;
+	astlpc->binding.name = "astlpc";
+	astlpc->binding.version = 1;
+	astlpc->binding.pkt_size =
+		MCTP_PACKET_SIZE(mtu > MCTP_BTU ? mtu : MCTP_BTU);
+	astlpc->binding.pkt_header = 4;
+	astlpc->binding.pkt_trailer = 4;
+	astlpc->binding.tx = mctp_binding_astlpc_tx;
+	if (mode == MCTP_BINDING_ASTLPC_MODE_BMC)
+		astlpc->binding.start = mctp_binding_astlpc_start_bmc;
+	else if (mode == MCTP_BINDING_ASTLPC_MODE_HOST)
+		astlpc->binding.start = mctp_binding_astlpc_start_host;
+	else {
+		astlpc_prerr(astlpc, "%s: Invalid mode: %d\n", __func__, mode);
+		__mctp_free(astlpc);
+		return NULL;
+	}
+
+	return astlpc;
+}
+
+struct mctp_binding *mctp_binding_astlpc_core(struct mctp_binding_astlpc *b)
+{
+	return &b->binding;
+}
+
+struct mctp_binding_astlpc *
+mctp_astlpc_init(uint8_t mode, uint32_t mtu, void *lpc_map,
+		 const struct mctp_binding_astlpc_ops *ops, void *ops_data)
+{
+	struct mctp_binding_astlpc *astlpc;
+
+	if (!(mode == MCTP_BINDING_ASTLPC_MODE_BMC ||
+	      mode == MCTP_BINDING_ASTLPC_MODE_HOST)) {
+		mctp_prerr("Unknown binding mode: %u", mode);
+		return NULL;
+	}
+
+	astlpc = __mctp_astlpc_init(mode, mtu);
+	if (!astlpc)
+		return NULL;
+
+	memcpy(&astlpc->ops, ops, sizeof(astlpc->ops));
+	astlpc->ops_data = ops_data;
+	astlpc->lpc_map = lpc_map;
+	astlpc->mode = mode;
+
+	return astlpc;
+}
+
+struct mctp_binding_astlpc *
+mctp_astlpc_init_ops(const struct mctp_binding_astlpc_ops *ops, void *ops_data,
+		     void *lpc_map)
+{
+	return mctp_astlpc_init(MCTP_BINDING_ASTLPC_MODE_BMC, MCTP_BTU, lpc_map,
+				ops, ops_data);
+}
+
+void mctp_astlpc_destroy(struct mctp_binding_astlpc *astlpc)
+{
+	/* Clear channel-active and bmc-ready */
+	if (astlpc->mode == MCTP_BINDING_ASTLPC_MODE_BMC)
+		mctp_astlpc_kcs_set_status(astlpc, 0);
+	__mctp_free(astlpc);
+}
+
+#ifdef MCTP_HAVE_FILEIO
+
+static int mctp_astlpc_init_fileio_lpc(struct mctp_binding_astlpc *astlpc)
+{
+	struct aspeed_lpc_ctrl_mapping map = {
+		.window_type = ASPEED_LPC_CTRL_WINDOW_MEMORY,
+		.window_id = 0, /* There's only one */
+		.flags = 0,
+		.addr = 0,
+		.offset = 0,
+		.size = 0
+	};
+	void *lpc_map_base;
+	int fd, rc;
+
+	fd = open(lpc_path, O_RDWR | O_SYNC);
+	if (fd < 0) {
+		astlpc_prwarn(astlpc, "LPC open (%s) failed", lpc_path);
+		return -1;
+	}
+
+	rc = ioctl(fd, ASPEED_LPC_CTRL_IOCTL_GET_SIZE, &map);
+	if (rc) {
+		astlpc_prwarn(astlpc, "LPC GET_SIZE failed");
+		close(fd);
+		return -1;
+	}
+
+	/*
+	 * 🚨🚨🚨
+	 *
+	 * Decouple ourselves from hiomapd[1] (another user of the FW2AHB) by
+	 * mapping the FW2AHB to the reserved memory here as well.
+	 *
+	 * It's not possible to use the MCTP ASTLPC binding on machines that
+	 * need the FW2AHB bridge mapped anywhere except to the reserved memory
+	 * (e.g. the host SPI NOR).
+	 *
+	 * [1] https://github.com/openbmc/hiomapd/
+	 *
+	 * 🚨🚨🚨
+	 *
+	 * The following calculation must align with what's going on in
+	 * hiomapd's lpc.c so as not to disrupt its behaviour:
+	 *
+	 * https://github.com/openbmc/hiomapd/blob/5ff50e3cbd7702aefc185264e4adfb9952040575/lpc.c#L68
+	 *
+	 * 🚨🚨🚨
+	 */
+
+	/* Map the reserved memory at the top of the 28-bit LPC firmware address space */
+	map.addr = 0x0FFFFFFF & -map.size;
+	astlpc_prinfo(
+		astlpc,
+		"Configuring FW2AHB to map reserved memory at 0x%08x for 0x%x in the LPC FW cycle address-space",
+		map.addr, map.size);
+
+	rc = ioctl(fd, ASPEED_LPC_CTRL_IOCTL_MAP, &map);
+	if (rc) {
+		astlpc_prwarn(astlpc,
+			      "Failed to map FW2AHB to reserved memory");
+		close(fd);
+		return -1;
+	}
+
+	/* Map the reserved memory into our address space */
+	lpc_map_base =
+		mmap(NULL, map.size, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
+	if (lpc_map_base == MAP_FAILED) {
+		astlpc_prwarn(astlpc, "LPC mmap failed");
+		rc = -1;
+	} else {
+		astlpc->lpc_map = lpc_map_base + map.size - LPC_WIN_SIZE;
+	}
+
+	close(fd);
+
+	return rc;
+}
+
+static int mctp_astlpc_init_fileio_kcs(struct mctp_binding_astlpc *astlpc)
+{
+	astlpc->kcs_fd = open(kcs_path, O_RDWR);
+	if (astlpc->kcs_fd < 0)
+		return -1;
+
+	return 0;
+}
+
+static int __mctp_astlpc_fileio_kcs_read(void *arg,
+					 enum mctp_binding_astlpc_kcs_reg reg,
+					 uint8_t *val)
+{
+	struct mctp_binding_astlpc *astlpc = arg;
+	off_t offset = reg;
+	int rc;
+
+	rc = pread(astlpc->kcs_fd, val, 1, offset);
+
+	return rc == 1 ? 0 : -1;
+}
+
+static int __mctp_astlpc_fileio_kcs_write(void *arg,
+					  enum mctp_binding_astlpc_kcs_reg reg,
+					  uint8_t val)
+{
+	struct mctp_binding_astlpc *astlpc = arg;
+	off_t offset = reg;
+	int rc;
+
+	rc = pwrite(astlpc->kcs_fd, &val, 1, offset);
+
+	return rc == 1 ? 0 : -1;
+}
+
+int mctp_astlpc_init_pollfd(struct mctp_binding_astlpc *astlpc,
+			    struct pollfd *pollfd)
+{
+	bool release;
+
+	pollfd->fd = astlpc->kcs_fd;
+	pollfd->events = 0;
+
+	release = astlpc->layout.rx.state == buffer_state_prepared ||
+		  astlpc->layout.tx.state == buffer_state_prepared;
+
+	pollfd->events = release ? POLLOUT : POLLIN;
+
+	return 0;
+}
+
+struct mctp_binding_astlpc *mctp_astlpc_init_fileio(void)
+{
+	struct mctp_binding_astlpc *astlpc;
+	int rc;
+
+	/*
+	 * If we're doing file IO then we're very likely not running
+	 * freestanding, so lets assume that we're on the BMC side.
+	 *
+	 * Requesting an MTU of 0 requests the largest possible MTU, whatever
+	 * value that might take.
+	 */
+	astlpc = __mctp_astlpc_init(MCTP_BINDING_ASTLPC_MODE_BMC, 0);
+	if (!astlpc)
+		return NULL;
+
+	/* Set internal operations for kcs. We use direct accesses to the lpc
+	 * map area */
+	astlpc->ops.kcs_read = __mctp_astlpc_fileio_kcs_read;
+	astlpc->ops.kcs_write = __mctp_astlpc_fileio_kcs_write;
+	astlpc->ops_data = astlpc;
+
+	rc = mctp_astlpc_init_fileio_lpc(astlpc);
+	if (rc) {
+		free(astlpc);
+		return NULL;
+	}
+
+	rc = mctp_astlpc_init_fileio_kcs(astlpc);
+	if (rc) {
+		free(astlpc);
+		return NULL;
+	}
+
+	return astlpc;
+}
+#else
+struct mctp_binding_astlpc *mctp_astlpc_init_fileio(void)
+{
+	mctp_prlog(MCTP_LOG_ERR, "%s: Missing support for file IO", __func__);
+	return NULL;
+}
+
+int mctp_astlpc_init_pollfd(struct mctp_binding_astlpc *astlpc __unused,
+			    struct pollfd *pollfd __unused)
+{
+	mctp_prlog(MCTP_LOG_ERR, "%s: Missing support for file IO", __func__);
+	return -1;
+}
+#endif
diff --git a/libmctp/config.h b/libmctp/config.h
new file mode 100644
index 00000000..3f4a6511
--- /dev/null
+++ b/libmctp/config.h
@@ -0,0 +1,59 @@
+/* Define to 1 if you have the <dlfcn.h> header file. */
+#undef HAVE_DLFCN_H
+
+/* use the ccan endian conversion functions rather than the BSD ones */
+#define HAVE_ENDIAN_H 1
+
+/* Define to 1 if you have the <fcntl.h> header file. */
+#undef HAVE_FCNTL_H
+
+/* Define to 1 if you have the <inttypes.h> header file. */
+#undef HAVE_INTTYPES_H
+
+/* Define to 1 if you have the <memory.h> header file. */
+#undef HAVE_MEMORY_H
+
+/* Define to 1 if you have the <stdint.h> header file. */
+#define HAVE_STDINT_H 1
+
+/* Define to 1 if you have the <stdlib.h> header file. */
+#undef HAVE_STDLIB_H
+
+/* Define to 1 if you have the <strings.h> header file. */
+#undef HAVE_STRINGS_H
+
+/* Define to 1 if you have the <string.h> header file. */
+#undef HAVE_STRING_H
+
+/* Define to 1 if you have the <sys/stat.h> header file. */
+#undef HAVE_SYS_STAT_H
+
+/* Define to 1 if you have the <sys/types.h> header file. */
+#undef HAVE_SYS_TYPES_H
+
+/* Define to 1 if you have the <unistd.h> header file. */
+#undef HAVE_UNISTD_H
+
+/* Define to use libc malloc and free for heap memory.
+ *
+ * NB: Skiboot's malloc() is defined as a macro and can't
+ *     be used directly.
+ */
+#undef MCTP_DEFAULT_ALLOC
+
+/* Support interfaces based on file-descriptors */
+#undef MCTP_HAVE_FILEIO
+
+/* Define to enable stdio functions */
+#undef MCTP_HAVE_STDIO
+
+/* Define to enable syslog */
+#undef MCTP_HAVE_SYSLOG
+
+/* Define to 1 if you have the ANSI C header files. */
+#undef STDC_HEADERS
+
+
+#include <opal-api.h>
+/* Convert POSIX / Linux errno codes used by libmctp to OPAL return codes */
+#define EHOSTDOWN (-OPAL_CLOSED)
diff --git a/libmctp/container_of.h b/libmctp/container_of.h
new file mode 100644
index 00000000..2abb3321
--- /dev/null
+++ b/libmctp/container_of.h
@@ -0,0 +1,9 @@
+#ifndef _CONTAINER_OF_H
+#define _CONTAINER_OF_H
+
+#ifndef container_of
+#define container_of(ptr, type, member)                                        \
+	(type *)((char *)(ptr) - (char *)&((type *)0)->member)
+#endif
+
+#endif
diff --git a/libmctp/core.c b/libmctp/core.c
new file mode 100644
index 00000000..2dfe3cce
--- /dev/null
+++ b/libmctp/core.c
@@ -0,0 +1,851 @@
+/* SPDX-License-Identifier: Apache-2.0 OR GPL-2.0-or-later */
+
+#include <assert.h>
+#include <errno.h>
+#include <stdarg.h>
+#include <stddef.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#undef pr_fmt
+#define pr_fmt(fmt) "core: " fmt
+
+#include "libmctp.h"
+#include "libmctp-alloc.h"
+#include "libmctp-log.h"
+#include "libmctp-cmds.h"
+#include "range.h"
+
+/* Internal data structures */
+
+struct mctp_bus {
+	mctp_eid_t eid;
+	struct mctp_binding *binding;
+	enum mctp_bus_state state;
+
+	struct mctp_pktbuf *tx_queue_head;
+	struct mctp_pktbuf *tx_queue_tail;
+
+	/* todo: routing */
+};
+
+struct mctp_msg_ctx {
+	uint8_t src;
+	uint8_t dest;
+	uint8_t tag;
+	uint8_t last_seq;
+	void *buf;
+	size_t buf_size;
+	size_t buf_alloc_size;
+	size_t fragment_size;
+};
+
+struct mctp {
+	int n_busses;
+	struct mctp_bus *busses;
+
+	/* Message RX callback */
+	mctp_rx_fn message_rx;
+	void *message_rx_data;
+
+	/* Packet capture callback */
+	mctp_capture_fn capture;
+	void *capture_data;
+
+	/* Message reassembly.
+	 * @todo: flexible context count
+	 */
+	struct mctp_msg_ctx msg_ctxs[16];
+
+	enum {
+		ROUTE_ENDPOINT,
+		ROUTE_BRIDGE,
+	} route_policy;
+	size_t max_message_size;
+};
+
+#ifndef BUILD_ASSERT
+#define BUILD_ASSERT(x)                                                        \
+	do {                                                                   \
+		(void)sizeof(char[0 - (!(x))]);                                \
+	} while (0)
+#endif
+
+#ifndef ARRAY_SIZE
+#define ARRAY_SIZE(a) (sizeof(a) / sizeof(a[0]))
+#endif
+
+/* 64kb should be sufficient for a single message. Applications
+ * requiring higher sizes can override by setting max_message_size.*/
+#ifndef MCTP_MAX_MESSAGE_SIZE
+#define MCTP_MAX_MESSAGE_SIZE 65536
+#endif
+
+static int mctp_message_tx_on_bus(struct mctp_bus *bus, mctp_eid_t src,
+				  mctp_eid_t dest, bool tag_owner,
+				  uint8_t msg_tag, void *msg, size_t msg_len);
+
+struct mctp_pktbuf *mctp_pktbuf_alloc(struct mctp_binding *binding, size_t len)
+{
+	struct mctp_pktbuf *buf;
+	size_t size;
+
+	size = len + binding->pkt_header + binding->pkt_trailer;
+
+	/* todo: pools */
+	buf = __mctp_alloc(sizeof(*buf) + size);
+
+	if (!buf)
+		return NULL;
+
+	buf->size = size;
+	buf->start = binding->pkt_header;
+	buf->end = buf->start + len;
+	buf->mctp_hdr_off = buf->start;
+	buf->next = NULL;
+
+	return buf;
+}
+
+void mctp_pktbuf_free(struct mctp_pktbuf *pkt)
+{
+	__mctp_free(pkt);
+}
+
+struct mctp_hdr *mctp_pktbuf_hdr(struct mctp_pktbuf *pkt)
+{
+	return (struct mctp_hdr *)(pkt->data + pkt->mctp_hdr_off);
+}
+
+void *mctp_pktbuf_data(struct mctp_pktbuf *pkt)
+{
+	return pkt->data + pkt->mctp_hdr_off + sizeof(struct mctp_hdr);
+}
+
+size_t mctp_pktbuf_size(struct mctp_pktbuf *pkt)
+{
+	return pkt->end - pkt->start;
+}
+
+void *mctp_pktbuf_alloc_start(struct mctp_pktbuf *pkt, size_t size)
+{
+	assert(size <= pkt->start);
+	pkt->start -= size;
+	return pkt->data + pkt->start;
+}
+
+void *mctp_pktbuf_alloc_end(struct mctp_pktbuf *pkt, size_t size)
+{
+	void *buf;
+
+	assert(size <= (pkt->size - pkt->end));
+	buf = pkt->data + pkt->end;
+	pkt->end += size;
+	return buf;
+}
+
+int mctp_pktbuf_push(struct mctp_pktbuf *pkt, void *data, size_t len)
+{
+	void *p;
+
+	if (pkt->end + len > pkt->size)
+		return -1;
+
+	p = pkt->data + pkt->end;
+
+	pkt->end += len;
+	memcpy(p, data, len);
+
+	return 0;
+}
+
+void *mctp_pktbuf_pop(struct mctp_pktbuf *pkt, size_t len)
+{
+	if (len > mctp_pktbuf_size(pkt))
+		return NULL;
+
+	pkt->end -= len;
+	return pkt->data + pkt->end;
+}
+
+/* Message reassembly */
+static struct mctp_msg_ctx *mctp_msg_ctx_lookup(struct mctp *mctp, uint8_t src,
+						uint8_t dest, uint8_t tag)
+{
+	unsigned int i;
+
+	/* @todo: better lookup, if we add support for more outstanding
+	 * message contexts */
+	for (i = 0; i < ARRAY_SIZE(mctp->msg_ctxs); i++) {
+		struct mctp_msg_ctx *ctx = &mctp->msg_ctxs[i];
+		if (ctx->src == src && ctx->dest == dest && ctx->tag == tag)
+			return ctx;
+	}
+
+	return NULL;
+}
+
+static struct mctp_msg_ctx *mctp_msg_ctx_create(struct mctp *mctp, uint8_t src,
+						uint8_t dest, uint8_t tag)
+{
+	struct mctp_msg_ctx *ctx = NULL;
+	unsigned int i;
+
+	for (i = 0; i < ARRAY_SIZE(mctp->msg_ctxs); i++) {
+		struct mctp_msg_ctx *tmp = &mctp->msg_ctxs[i];
+		if (!tmp->src) {
+			ctx = tmp;
+			break;
+		}
+	}
+
+	if (!ctx)
+		return NULL;
+
+	ctx->src = src;
+	ctx->dest = dest;
+	ctx->tag = tag;
+	ctx->buf_size = 0;
+
+	return ctx;
+}
+
+static void mctp_msg_ctx_drop(struct mctp_msg_ctx *ctx)
+{
+	ctx->src = 0;
+}
+
+static void mctp_msg_ctx_reset(struct mctp_msg_ctx *ctx)
+{
+	ctx->buf_size = 0;
+	ctx->fragment_size = 0;
+}
+
+static int mctp_msg_ctx_add_pkt(struct mctp_msg_ctx *ctx,
+				struct mctp_pktbuf *pkt, size_t max_size)
+{
+	size_t len;
+
+	len = mctp_pktbuf_size(pkt) - sizeof(struct mctp_hdr);
+
+	if (len + ctx->buf_size < ctx->buf_size) {
+		return -1;
+	}
+
+	if (ctx->buf_size + len > ctx->buf_alloc_size) {
+		size_t new_alloc_size;
+		void *lbuf;
+
+		/* @todo: finer-grained allocation */
+		if (!ctx->buf_alloc_size) {
+			new_alloc_size = MAX(len, 4096UL);
+		} else {
+			new_alloc_size = MAX(ctx->buf_alloc_size * 2,
+					     len + ctx->buf_size);
+		}
+
+		/* Don't allow heap to grow beyond a limit */
+		if (new_alloc_size > max_size)
+			return -1;
+
+		lbuf = __mctp_realloc(ctx->buf, new_alloc_size);
+		if (lbuf) {
+			ctx->buf = lbuf;
+			ctx->buf_alloc_size = new_alloc_size;
+		} else {
+			__mctp_free(ctx->buf);
+			return -1;
+		}
+	}
+
+	memcpy((uint8_t *)ctx->buf + ctx->buf_size, mctp_pktbuf_data(pkt), len);
+	ctx->buf_size += len;
+
+	return 0;
+}
+
+/* Core API functions */
+struct mctp *mctp_init(void)
+{
+	struct mctp *mctp;
+
+	mctp = __mctp_alloc(sizeof(*mctp));
+
+	if (!mctp)
+		return NULL;
+
+	memset(mctp, 0, sizeof(*mctp));
+	mctp->max_message_size = MCTP_MAX_MESSAGE_SIZE;
+
+	return mctp;
+}
+
+void mctp_set_max_message_size(struct mctp *mctp, size_t message_size)
+{
+	mctp->max_message_size = message_size;
+}
+
+void mctp_set_capture_handler(struct mctp *mctp, mctp_capture_fn fn, void *user)
+{
+	mctp->capture = fn;
+	mctp->capture_data = user;
+}
+
+static void mctp_bus_destroy(struct mctp_bus *bus)
+{
+	while (bus->tx_queue_head) {
+		struct mctp_pktbuf *curr = bus->tx_queue_head;
+
+		bus->tx_queue_head = curr->next;
+		mctp_pktbuf_free(curr);
+	}
+}
+
+void mctp_destroy(struct mctp *mctp)
+{
+	size_t i;
+
+	/* Cleanup message assembly contexts */
+	BUILD_ASSERT(ARRAY_SIZE(mctp->msg_ctxs) < SIZE_MAX);
+	for (i = 0; i < ARRAY_SIZE(mctp->msg_ctxs); i++) {
+		struct mctp_msg_ctx *tmp = &mctp->msg_ctxs[i];
+		if (tmp->buf)
+			__mctp_free(tmp->buf);
+	}
+
+	while (mctp->n_busses--)
+		mctp_bus_destroy(&mctp->busses[mctp->n_busses]);
+
+	__mctp_free(mctp->busses);
+	__mctp_free(mctp);
+}
+
+int mctp_set_rx_all(struct mctp *mctp, mctp_rx_fn fn, void *data)
+{
+	mctp->message_rx = fn;
+	mctp->message_rx_data = data;
+	return 0;
+}
+
+static struct mctp_bus *find_bus_for_eid(struct mctp *mctp, mctp_eid_t dest
+					 __attribute__((unused)))
+{
+	if (mctp->n_busses == 0)
+		return NULL;
+
+	/* for now, just use the first bus. For full routing support,
+	 * we will need a table of neighbours */
+	return &mctp->busses[0];
+}
+
+int mctp_register_bus(struct mctp *mctp, struct mctp_binding *binding,
+		      mctp_eid_t eid)
+{
+	int rc = 0;
+
+	/* todo: multiple busses */
+	assert(mctp->n_busses == 0);
+	mctp->n_busses = 1;
+
+	mctp->busses = __mctp_alloc(sizeof(struct mctp_bus));
+	if (!mctp->busses)
+		return -ENOMEM;
+
+	memset(mctp->busses, 0, sizeof(struct mctp_bus));
+	mctp->busses[0].binding = binding;
+	mctp->busses[0].eid = eid;
+	binding->bus = &mctp->busses[0];
+	binding->mctp = mctp;
+	mctp->route_policy = ROUTE_ENDPOINT;
+
+	if (binding->start) {
+		rc = binding->start(binding);
+		if (rc < 0) {
+			mctp_prerr("Failed to start binding: %d", rc);
+			binding->bus = NULL;
+			__mctp_free(mctp->busses);
+			mctp->busses = NULL;
+			mctp->n_busses = 0;
+		}
+	}
+
+	return rc;
+}
+
+void mctp_unregister_bus(struct mctp *mctp, struct mctp_binding *binding)
+{
+	/*
+	 * We only support one bus right now; once the call completes we will
+	 * have no more busses
+	 */
+	mctp->n_busses = 0;
+	binding->mctp = NULL;
+	binding->bus = NULL;
+	free(mctp->busses);
+}
+
+int mctp_bridge_busses(struct mctp *mctp, struct mctp_binding *b1,
+		       struct mctp_binding *b2)
+{
+	int rc = 0;
+
+	assert(mctp->n_busses == 0);
+	mctp->busses = __mctp_alloc(2 * sizeof(struct mctp_bus));
+	if (!mctp->busses)
+		return -ENOMEM;
+	memset(mctp->busses, 0, 2 * sizeof(struct mctp_bus));
+	mctp->n_busses = 2;
+	mctp->busses[0].binding = b1;
+	b1->bus = &mctp->busses[0];
+	b1->mctp = mctp;
+	mctp->busses[1].binding = b2;
+	b2->bus = &mctp->busses[1];
+	b2->mctp = mctp;
+
+	mctp->route_policy = ROUTE_BRIDGE;
+
+	if (b1->start) {
+		rc = b1->start(b1);
+		if (rc < 0) {
+			mctp_prerr("Failed to start bridged bus %s: %d",
+				   b1->name, rc);
+			goto done;
+		}
+	}
+
+	if (b2->start) {
+		rc = b2->start(b2);
+		if (rc < 0) {
+			mctp_prerr("Failed to start bridged bus %s: %d",
+				   b2->name, rc);
+			goto done;
+		}
+	}
+
+done:
+	return rc;
+}
+
+static inline bool mctp_ctrl_cmd_is_transport(struct mctp_ctrl_msg_hdr *hdr)
+{
+	return ((hdr->command_code >= MCTP_CTRL_CMD_FIRST_TRANSPORT) &&
+		(hdr->command_code <= MCTP_CTRL_CMD_LAST_TRANSPORT));
+}
+
+static bool mctp_ctrl_handle_msg(struct mctp_bus *bus, mctp_eid_t src,
+				 uint8_t msg_tag, bool tag_owner, void *buffer,
+				 size_t length)
+{
+	struct mctp_ctrl_msg_hdr *msg_hdr = buffer;
+
+	/*
+	 * Control message is received. If a transport control message handler
+	 * is provided, it will called. If there is no dedicated handler, this
+	 * function returns false and data can be handled by the generic
+	 * message handler. The transport control message handler will be
+	 * provided with messages in the command range 0xF0 - 0xFF.
+	 */
+	if (mctp_ctrl_cmd_is_transport(msg_hdr)) {
+		if (bus->binding->control_rx != NULL) {
+			/* MCTP bus binding handler */
+			bus->binding->control_rx(src, msg_tag, tag_owner,
+						 bus->binding->control_rx_data,
+						 buffer, length);
+			return true;
+		}
+	}
+
+	/*
+	 * Command was not handled, due to lack of specific callback.
+	 * It will be passed to regular message_rx handler.
+	 */
+	return false;
+}
+
+static inline bool mctp_rx_dest_is_local(struct mctp_bus *bus, mctp_eid_t dest)
+{
+	return dest == bus->eid || dest == MCTP_EID_NULL ||
+	       dest == MCTP_EID_BROADCAST;
+}
+
+static inline bool mctp_ctrl_cmd_is_request(struct mctp_ctrl_msg_hdr *hdr)
+{
+	return hdr->ic_msg_type == MCTP_CTRL_HDR_MSG_TYPE &&
+	       hdr->rq_dgram_inst & MCTP_CTRL_HDR_FLAG_REQUEST;
+}
+
+/*
+ * Receive the complete MCTP message and route it.
+ * Asserts:
+ *     'buf' is not NULL.
+ */
+static void mctp_rx(struct mctp *mctp, struct mctp_bus *bus, mctp_eid_t src,
+		    mctp_eid_t dest, bool tag_owner, uint8_t msg_tag, void *buf,
+		    size_t len)
+{
+	assert(buf != NULL);
+
+	if (mctp->route_policy == ROUTE_ENDPOINT &&
+	    mctp_rx_dest_is_local(bus, dest)) {
+		/* Handle MCTP Control Messages: */
+		if (len >= sizeof(struct mctp_ctrl_msg_hdr)) {
+			struct mctp_ctrl_msg_hdr *msg_hdr = buf;
+
+			/*
+			 * Identify if this is a control request message.
+			 * See DSP0236 v1.3.0 sec. 11.5.
+			 */
+			if (mctp_ctrl_cmd_is_request(msg_hdr)) {
+				bool handled;
+				handled = mctp_ctrl_handle_msg(
+					bus, src, msg_tag, tag_owner, buf, len);
+				if (handled)
+					return;
+			}
+		}
+
+		if (mctp->message_rx)
+			mctp->message_rx(src, tag_owner, msg_tag,
+					 mctp->message_rx_data, buf, len);
+	}
+
+	if (mctp->route_policy == ROUTE_BRIDGE) {
+		int i;
+
+		for (i = 0; i < mctp->n_busses; i++) {
+			struct mctp_bus *dest_bus = &mctp->busses[i];
+			if (dest_bus == bus)
+				continue;
+
+			mctp_message_tx_on_bus(dest_bus, src, dest, tag_owner,
+					       msg_tag, buf, len);
+		}
+	}
+}
+
+void mctp_bus_rx(struct mctp_binding *binding, struct mctp_pktbuf *pkt)
+{
+	struct mctp_bus *bus = binding->bus;
+	struct mctp *mctp = binding->mctp;
+	uint8_t flags, exp_seq, seq, tag;
+	struct mctp_msg_ctx *ctx;
+	struct mctp_hdr *hdr;
+	bool tag_owner;
+	size_t len;
+	void *p;
+	int rc;
+
+	assert(bus);
+
+	/* Drop packet if it was smaller than mctp hdr size */
+	if (mctp_pktbuf_size(pkt) <= sizeof(struct mctp_hdr))
+		goto out;
+
+	if (mctp->capture)
+		mctp->capture(pkt, MCTP_MESSAGE_CAPTURE_INCOMING,
+			      mctp->capture_data);
+
+	hdr = mctp_pktbuf_hdr(pkt);
+
+	/* small optimisation: don't bother reassembly if we're going to
+	 * drop the packet in mctp_rx anyway */
+	if (mctp->route_policy == ROUTE_ENDPOINT && hdr->dest != bus->eid)
+		goto out;
+
+	flags = hdr->flags_seq_tag & (MCTP_HDR_FLAG_SOM | MCTP_HDR_FLAG_EOM);
+	tag = (hdr->flags_seq_tag >> MCTP_HDR_TAG_SHIFT) & MCTP_HDR_TAG_MASK;
+	seq = (hdr->flags_seq_tag >> MCTP_HDR_SEQ_SHIFT) & MCTP_HDR_SEQ_MASK;
+	tag_owner = (hdr->flags_seq_tag >> MCTP_HDR_TO_SHIFT) &
+		    MCTP_HDR_TO_MASK;
+
+	switch (flags) {
+	case MCTP_HDR_FLAG_SOM | MCTP_HDR_FLAG_EOM:
+		/* single-packet message - send straight up to rx function,
+		 * no need to create a message context */
+		len = pkt->end - pkt->mctp_hdr_off - sizeof(struct mctp_hdr);
+		p = pkt->data + pkt->mctp_hdr_off + sizeof(struct mctp_hdr);
+		mctp_rx(mctp, bus, hdr->src, hdr->dest, tag_owner, tag, p, len);
+		break;
+
+	case MCTP_HDR_FLAG_SOM:
+		/* start of a new message - start the new context for
+		 * future message reception. If an existing context is
+		 * already present, drop it. */
+		ctx = mctp_msg_ctx_lookup(mctp, hdr->src, hdr->dest, tag);
+		if (ctx) {
+			mctp_msg_ctx_reset(ctx);
+		} else {
+			ctx = mctp_msg_ctx_create(mctp, hdr->src, hdr->dest,
+						  tag);
+			/* If context creation fails due to exhaution of contexts we
+			* can support, drop the packet */
+			if (!ctx) {
+				mctp_prdebug("Context buffers exhausted.");
+				goto out;
+			}
+		}
+
+		/* Save the fragment size, subsequent middle fragments
+		 * should of the same size */
+		ctx->fragment_size = mctp_pktbuf_size(pkt);
+
+		rc = mctp_msg_ctx_add_pkt(ctx, pkt, mctp->max_message_size);
+		if (rc) {
+			mctp_msg_ctx_drop(ctx);
+		} else {
+			ctx->last_seq = seq;
+		}
+
+		break;
+
+	case MCTP_HDR_FLAG_EOM:
+		ctx = mctp_msg_ctx_lookup(mctp, hdr->src, hdr->dest, tag);
+		if (!ctx)
+			goto out;
+
+		exp_seq = (ctx->last_seq + 1) % 4;
+
+		if (exp_seq != seq) {
+			mctp_prdebug(
+				"Sequence number %d does not match expected %d",
+				seq, exp_seq);
+			mctp_msg_ctx_drop(ctx);
+			goto out;
+		}
+
+		len = mctp_pktbuf_size(pkt);
+
+		if (len > ctx->fragment_size) {
+			mctp_prdebug("Unexpected fragment size. Expected"
+				     " less than %zu, received = %zu",
+				     ctx->fragment_size, len);
+			mctp_msg_ctx_drop(ctx);
+			goto out;
+		}
+
+		rc = mctp_msg_ctx_add_pkt(ctx, pkt, mctp->max_message_size);
+		if (!rc)
+			mctp_rx(mctp, bus, ctx->src, ctx->dest, tag_owner, tag,
+				ctx->buf, ctx->buf_size);
+
+		mctp_msg_ctx_drop(ctx);
+		break;
+
+	case 0:
+		/* Neither SOM nor EOM */
+		ctx = mctp_msg_ctx_lookup(mctp, hdr->src, hdr->dest, tag);
+		if (!ctx)
+			goto out;
+
+		exp_seq = (ctx->last_seq + 1) % 4;
+		if (exp_seq != seq) {
+			mctp_prdebug(
+				"Sequence number %d does not match expected %d",
+				seq, exp_seq);
+			mctp_msg_ctx_drop(ctx);
+			goto out;
+		}
+
+		len = mctp_pktbuf_size(pkt);
+
+		if (len != ctx->fragment_size) {
+			mctp_prdebug("Unexpected fragment size. Expected = %zu "
+				     "received = %zu",
+				     ctx->fragment_size, len);
+			mctp_msg_ctx_drop(ctx);
+			goto out;
+		}
+
+		rc = mctp_msg_ctx_add_pkt(ctx, pkt, mctp->max_message_size);
+		if (rc) {
+			mctp_msg_ctx_drop(ctx);
+			goto out;
+		}
+		ctx->last_seq = seq;
+
+		break;
+	}
+out:
+	mctp_pktbuf_free(pkt);
+}
+
+static int mctp_packet_tx(struct mctp_bus *bus, struct mctp_pktbuf *pkt)
+{
+	struct mctp *mctp = bus->binding->mctp;
+
+	if (bus->state != mctp_bus_state_tx_enabled)
+		return -1;
+
+	if (mctp->capture)
+		mctp->capture(pkt, MCTP_MESSAGE_CAPTURE_OUTGOING,
+			      mctp->capture_data);
+
+	return bus->binding->tx(bus->binding, pkt);
+}
+
+static void mctp_send_tx_queue(struct mctp_bus *bus)
+{
+	struct mctp_pktbuf *pkt;
+
+	while ((pkt = bus->tx_queue_head)) {
+		int rc;
+
+		rc = mctp_packet_tx(bus, pkt);
+		switch (rc) {
+		/* If transmission succeded, or */
+		case 0:
+		/* If the packet is somehow too large */
+		case -EMSGSIZE:
+			/* Drop the packet */
+			bus->tx_queue_head = pkt->next;
+			mctp_pktbuf_free(pkt);
+			break;
+
+		/* If the binding was busy, or */
+		case -EBUSY:
+		/* Some other unknown error occurred */
+		default:
+			/* Make sure the tail pointer is consistent and retry later */
+			goto cleanup_tail;
+		};
+	}
+
+cleanup_tail:
+	if (!bus->tx_queue_head)
+		bus->tx_queue_tail = NULL;
+}
+
+void mctp_binding_set_tx_enabled(struct mctp_binding *binding, bool enable)
+{
+	struct mctp_bus *bus = binding->bus;
+
+	switch (bus->state) {
+	case mctp_bus_state_constructed:
+		if (!enable)
+			return;
+
+		if (binding->pkt_size < MCTP_PACKET_SIZE(MCTP_BTU)) {
+			mctp_prerr(
+				"Cannot start %s binding with invalid MTU: %zu",
+				binding->name,
+				MCTP_BODY_SIZE(binding->pkt_size));
+			return;
+		}
+
+		bus->state = mctp_bus_state_tx_enabled;
+		mctp_prinfo("%s binding started", binding->name);
+		return;
+	case mctp_bus_state_tx_enabled:
+		if (enable)
+			return;
+
+		bus->state = mctp_bus_state_tx_disabled;
+		mctp_prdebug("%s binding Tx disabled", binding->name);
+		return;
+	case mctp_bus_state_tx_disabled:
+		if (!enable)
+			return;
+
+		bus->state = mctp_bus_state_tx_enabled;
+		mctp_prdebug("%s binding Tx enabled", binding->name);
+		mctp_send_tx_queue(bus);
+		return;
+	}
+}
+
+enum mctp_bus_state mctp_bus_get_state(struct mctp_bus *bus)
+{
+	return bus->state;
+}
+
+static int mctp_message_tx_on_bus(struct mctp_bus *bus, mctp_eid_t src,
+				  mctp_eid_t dest, bool tag_owner,
+				  uint8_t msg_tag, void *msg, size_t msg_len)
+{
+	size_t max_payload_len, payload_len, p;
+	struct mctp_pktbuf *pkt;
+	struct mctp_hdr *hdr;
+	int i;
+
+	if (bus->state == mctp_bus_state_constructed)
+		return -ENXIO;
+
+	if ((msg_tag & MCTP_HDR_TAG_MASK) != msg_tag)
+		return -EINVAL;
+
+	max_payload_len = MCTP_BODY_SIZE(bus->binding->pkt_size);
+
+	{
+		const bool valid_mtu = max_payload_len >= MCTP_BTU;
+		assert(valid_mtu);
+		if (!valid_mtu)
+			return -EINVAL;
+	}
+
+	mctp_prdebug(
+		"%s: Generating packets for transmission of %zu byte message from %hhu to %hhu",
+		__func__, msg_len, src, dest);
+
+	/* queue up packets, each of max MCTP_MTU size */
+	for (p = 0, i = 0; p < msg_len; i++) {
+		payload_len = msg_len - p;
+		if (payload_len > max_payload_len)
+			payload_len = max_payload_len;
+
+		pkt = mctp_pktbuf_alloc(bus->binding,
+					payload_len + sizeof(*hdr));
+		hdr = mctp_pktbuf_hdr(pkt);
+
+		hdr->ver = bus->binding->version & 0xf;
+		hdr->dest = dest;
+		hdr->src = src;
+		hdr->flags_seq_tag = (tag_owner << MCTP_HDR_TO_SHIFT) |
+				     (msg_tag << MCTP_HDR_TAG_SHIFT);
+
+		if (i == 0)
+			hdr->flags_seq_tag |= MCTP_HDR_FLAG_SOM;
+		if (p + payload_len >= msg_len)
+			hdr->flags_seq_tag |= MCTP_HDR_FLAG_EOM;
+		hdr->flags_seq_tag |= (i & MCTP_HDR_SEQ_MASK)
+				      << MCTP_HDR_SEQ_SHIFT;
+
+		memcpy(mctp_pktbuf_data(pkt), (uint8_t *)msg + p, payload_len);
+
+		/* add to tx queue */
+		if (bus->tx_queue_tail)
+			bus->tx_queue_tail->next = pkt;
+		else
+			bus->tx_queue_head = pkt;
+		bus->tx_queue_tail = pkt;
+
+		p += payload_len;
+	}
+
+	mctp_prdebug("%s: Enqueued %d packets", __func__, i);
+
+	mctp_send_tx_queue(bus);
+
+	return 0;
+}
+
+int mctp_message_tx(struct mctp *mctp, mctp_eid_t eid, bool tag_owner,
+		    uint8_t msg_tag, void *msg, size_t msg_len)
+{
+	struct mctp_bus *bus;
+
+	/* TODO: Protect against same tag being used across
+	 * different callers */
+	if ((msg_tag & MCTP_HDR_TAG_MASK) != msg_tag) {
+		mctp_prerr("Incorrect message tag %u passed.", msg_tag);
+		return -EINVAL;
+	}
+
+	bus = find_bus_for_eid(mctp, eid);
+	if (!bus)
+		return 0;
+
+	return mctp_message_tx_on_bus(bus, bus->eid, eid, tag_owner, msg_tag,
+				      msg, msg_len);
+}
diff --git a/libmctp/crc32.c b/libmctp/crc32.c
new file mode 100644
index 00000000..b5883c28
--- /dev/null
+++ b/libmctp/crc32.c
@@ -0,0 +1,25 @@
+/* SPDX-License-Identifier: Apache-2.0 */
+/* Copyright 2021 IBM Corp. */
+
+#include "crc32.h"
+
+#include <limits.h>
+
+/* Very dumb CRC-32 implementation */
+uint32_t crc32(const void *buf, size_t len)
+{
+	const uint8_t *buf8 = buf;
+	uint32_t rem = 0xffffffff;
+
+	for (; len; len--) {
+		int i;
+
+		rem = rem ^ *buf8;
+		for (i = 0; i < CHAR_BIT; i++)
+			rem = (rem >> 1) ^ ((rem & 1) * 0xEDB88320);
+
+		buf8++;
+	}
+
+	return rem ^ 0xffffffff;
+}
diff --git a/libmctp/crc32.h b/libmctp/crc32.h
new file mode 100644
index 00000000..c47a27ea
--- /dev/null
+++ b/libmctp/crc32.h
@@ -0,0 +1,9 @@
+#ifndef _CRC32_H
+#define _CRC32_H
+
+#include <stddef.h>
+#include <stdint.h>
+
+uint32_t crc32(const void *buf, size_t len);
+
+#endif
diff --git a/libmctp/libmctp-alloc.h b/libmctp/libmctp-alloc.h
new file mode 100644
index 00000000..2532cfa9
--- /dev/null
+++ b/libmctp/libmctp-alloc.h
@@ -0,0 +1,12 @@
+/* SPDX-License-Identifier: Apache-2.0 OR GPL-2.0-or-later */
+
+#ifndef _LIBMCTP_ALLOC_H
+#define _LIBMCTP_ALLOC_H
+
+#include <stdlib.h>
+
+void *__mctp_alloc(size_t size);
+void __mctp_free(void *ptr);
+void *__mctp_realloc(void *ptr, size_t size);
+
+#endif /* _LIBMCTP_ALLOC_H */
diff --git a/libmctp/libmctp-astlpc.h b/libmctp/libmctp-astlpc.h
new file mode 100644
index 00000000..110b998a
--- /dev/null
+++ b/libmctp/libmctp-astlpc.h
@@ -0,0 +1,58 @@
+/* SPDX-License-Identifier: Apache-2.0 OR GPL-2.0-or-later */
+
+#ifndef _LIBMCTP_ASTLPCL_H
+#define _LIBMCTP_ASTLPCL_H
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#include <libmctp.h>
+
+#include <stdint.h>
+
+struct mctp_binding_astlpc;
+
+/* todo: Remove enum from public interfaces */
+enum mctp_binding_astlpc_kcs_reg {
+	MCTP_ASTLPC_KCS_REG_DATA = 0,
+	MCTP_ASTLPC_KCS_REG_STATUS = 1,
+};
+
+struct mctp_binding_astlpc_ops {
+	int (*kcs_read)(void *data, enum mctp_binding_astlpc_kcs_reg reg,
+			uint8_t *val);
+	int (*kcs_write)(void *data, enum mctp_binding_astlpc_kcs_reg reg,
+			 uint8_t val);
+	int (*lpc_read)(void *data, void *buf, long offset, size_t len);
+	int (*lpc_write)(void *data, const void *buf, long offset, size_t len);
+};
+
+#define MCTP_BINDING_ASTLPC_MODE_BMC  0
+#define MCTP_BINDING_ASTLPC_MODE_HOST 1
+struct mctp_binding_astlpc *
+mctp_astlpc_init(uint8_t mode, uint32_t mtu, void *lpc_map,
+		 const struct mctp_binding_astlpc_ops *ops, void *ops_data);
+
+struct mctp_binding_astlpc *
+mctp_astlpc_init_ops(const struct mctp_binding_astlpc_ops *ops, void *ops_data,
+		     void *lpc_map);
+void mctp_astlpc_destroy(struct mctp_binding_astlpc *astlpc);
+
+struct mctp_binding *mctp_binding_astlpc_core(struct mctp_binding_astlpc *b);
+
+bool mctp_astlpc_tx_done(struct mctp_binding_astlpc *astlpc);
+int mctp_astlpc_poll(struct mctp_binding_astlpc *astlpc);
+
+/* fileio-based interface */
+struct mctp_binding_astlpc *mctp_astlpc_init_fileio(void);
+
+struct pollfd;
+int mctp_astlpc_init_pollfd(struct mctp_binding_astlpc *astlpc,
+			    struct pollfd *pollfd);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* _LIBMCTP_ASTLPC_H */
diff --git a/libmctp/libmctp-cmds.h b/libmctp/libmctp-cmds.h
new file mode 100644
index 00000000..293aca4d
--- /dev/null
+++ b/libmctp/libmctp-cmds.h
@@ -0,0 +1,74 @@
+/* SPDX-License-Identifier: Apache-2.0 OR GPL-2.0-or-later */
+#ifndef _LIBMCTP_CMDS_H
+#define _LIBMCTP_CMDS_H
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#include "libmctp.h"
+
+/*
+ * Helper structs and functions for MCTP control messages.
+ * See DSP0236 v1.3.0 sec. 11 for reference.
+ */
+
+struct mctp_ctrl_msg_hdr {
+	uint8_t ic_msg_type;
+	uint8_t rq_dgram_inst;
+	uint8_t command_code;
+	uint8_t completion_code;
+};
+
+#define MCTP_CTRL_HDR_MSG_TYPE	       0
+#define MCTP_CTRL_HDR_FLAG_REQUEST     (1 << 7)
+#define MCTP_CTRL_HDR_FLAG_DGRAM       (1 << 6)
+#define MCTP_CTRL_HDR_INSTANCE_ID_MASK 0x1F
+
+/*
+ * MCTP Control Command IDs
+ * See DSP0236 v1.3.0 Table 12.
+ */
+#define MCTP_CTRL_CMD_RESERVED			 0x00
+#define MCTP_CTRL_CMD_SET_ENDPOINT_ID		 0x01
+#define MCTP_CTRL_CMD_GET_ENDPOINT_ID		 0x02
+#define MCTP_CTRL_CMD_GET_ENDPOINT_UUID		 0x03
+#define MCTP_CTRL_CMD_GET_VERSION_SUPPORT	 0x04
+#define MCTP_CTRL_CMD_GET_MESSAGE_TYPE_SUPPORT	 0x05
+#define MCTP_CTRL_CMD_GET_VENDOR_MESSAGE_SUPPORT 0x06
+#define MCTP_CTRL_CMD_RESOLVE_ENDPOINT_ID	 0x07
+#define MCTP_CTRL_CMD_ALLOCATE_ENDPOINT_IDS	 0x08
+#define MCTP_CTRL_CMD_ROUTING_INFO_UPDATE	 0x09
+#define MCTP_CTRL_CMD_GET_ROUTING_TABLE_ENTRIES	 0x0A
+#define MCTP_CTRL_CMD_PREPARE_ENDPOINT_DISCOVERY 0x0B
+#define MCTP_CTRL_CMD_ENDPOINT_DISCOVERY	 0x0C
+#define MCTP_CTRL_CMD_DISCOVERY_NOTIFY		 0x0D
+#define MCTP_CTRL_CMD_GET_NETWORK_ID		 0x0E
+#define MCTP_CTRL_CMD_QUERY_HOP			 0x0F
+#define MCTP_CTRL_CMD_RESOLVE_UUID		 0x10
+#define MCTP_CTRL_CMD_QUERY_RATE_LIMIT		 0x11
+#define MCTP_CTRL_CMD_REQUEST_TX_RATE_LIMIT	 0x12
+#define MCTP_CTRL_CMD_UPDATE_RATE_LIMIT		 0x13
+#define MCTP_CTRL_CMD_QUERY_SUPPORTED_INTERFACES 0x14
+#define MCTP_CTRL_CMD_MAX			 0x15
+/* 0xF0 - 0xFF are transport specific */
+#define MCTP_CTRL_CMD_FIRST_TRANSPORT 0xF0
+#define MCTP_CTRL_CMD_LAST_TRANSPORT  0xFF
+
+/*
+ * MCTP Control Completion Codes
+ * See DSP0236 v1.3.0 Table 13.
+ */
+#define MCTP_CTRL_CC_SUCCESS		   0x00
+#define MCTP_CTRL_CC_ERROR		   0x01
+#define MCTP_CTRL_CC_ERROR_INVALID_DATA	   0x02
+#define MCTP_CTRL_CC_ERROR_INVALID_LENGTH  0x03
+#define MCTP_CTRL_CC_ERROR_NOT_READY	   0x04
+#define MCTP_CTRL_CC_ERROR_UNSUPPORTED_CMD 0x05
+/* 0x80 - 0xFF are command specific */
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* _LIBMCTP_CMDS_H */
diff --git a/libmctp/libmctp-log.h b/libmctp/libmctp-log.h
new file mode 100644
index 00000000..1e574e5e
--- /dev/null
+++ b/libmctp/libmctp-log.h
@@ -0,0 +1,24 @@
+/* SPDX-License-Identifier: Apache-2.0 OR GPL-2.0-or-later */
+
+#ifndef _LIBMCTP_LOG_H
+#define _LIBMCTP_LOG_H
+
+/* libmctp-internal logging */
+
+void mctp_prlog(int level, const char *fmt, ...)
+	__attribute__((format(printf, 2, 3)));
+
+#ifndef pr_fmt
+#define pr_fmt(x) x
+#endif
+
+#define mctp_prerr(fmt, ...)                                                   \
+	mctp_prlog(MCTP_LOG_ERR, pr_fmt(fmt), ##__VA_ARGS__)
+#define mctp_prwarn(fmt, ...)                                                  \
+	mctp_prlog(MCTP_LOG_WARNING, pr_fmt(fmt), ##__VA_ARGS__)
+#define mctp_prinfo(fmt, ...)                                                  \
+	mctp_prlog(MCTP_LOG_INFO, pr_fmt(fmt), ##__VA_ARGS__)
+#define mctp_prdebug(fmt, ...)                                                 \
+	mctp_prlog(MCTP_LOG_DEBUG, pr_fmt(fmt), ##__VA_ARGS__)
+
+#endif /* _LIBMCTP_LOG_H */
diff --git a/libmctp/libmctp-serial.h b/libmctp/libmctp-serial.h
new file mode 100644
index 00000000..dc7cb995
--- /dev/null
+++ b/libmctp/libmctp-serial.h
@@ -0,0 +1,40 @@
+/* SPDX-License-Identifier: Apache-2.0 OR GPL-2.0-or-later */
+
+#ifndef _LIBMCTP_SERIAL_H
+#define _LIBMCTP_SERIAL_H
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#include <libmctp.h>
+
+struct mctp_binding_serial;
+
+struct mctp_binding_serial *mctp_serial_init(void);
+void mctp_serial_destroy(struct mctp_binding_serial *serial);
+
+struct mctp_binding *mctp_binding_serial_core(struct mctp_binding_serial *b);
+
+/* file-based IO */
+struct pollfd;
+int mctp_serial_init_pollfd(struct mctp_binding_serial *serial,
+			    struct pollfd *pollfd);
+
+int mctp_serial_read(struct mctp_binding_serial *serial);
+int mctp_serial_open_path(struct mctp_binding_serial *serial, const char *path);
+void mctp_serial_open_fd(struct mctp_binding_serial *serial, int fd);
+
+/* direct function call IO */
+typedef int (*mctp_serial_tx_fn)(void *data, void *buf, size_t len)
+	__attribute__((warn_unused_result));
+void mctp_serial_set_tx_fn(struct mctp_binding_serial *serial,
+			   mctp_serial_tx_fn fn, void *data);
+int mctp_serial_rx(struct mctp_binding_serial *serial, const void *buf,
+		   size_t len);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* _LIBMCTP_SERIAL_H */
diff --git a/libmctp/libmctp.h b/libmctp/libmctp.h
new file mode 100644
index 00000000..d62d698d
--- /dev/null
+++ b/libmctp/libmctp.h
@@ -0,0 +1,174 @@
+/* SPDX-License-Identifier: Apache-2.0 OR GPL-2.0-or-later */
+
+#ifndef _LIBMCTP_H
+#define _LIBMCTP_H
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#include <stdarg.h>
+#include <stdbool.h>
+#include <stdint.h>
+#include <stddef.h>
+
+typedef uint8_t mctp_eid_t;
+
+/* Special Endpoint ID values */
+#define MCTP_EID_NULL	   0
+#define MCTP_EID_BROADCAST 0xff
+
+/* MCTP packet definitions */
+struct mctp_hdr {
+	uint8_t ver;
+	uint8_t dest;
+	uint8_t src;
+	uint8_t flags_seq_tag;
+};
+
+/* Definitions for flags_seq_tag field */
+#define MCTP_HDR_FLAG_SOM  (1 << 7)
+#define MCTP_HDR_FLAG_EOM  (1 << 6)
+#define MCTP_HDR_FLAG_TO   (1 << 3)
+#define MCTP_HDR_TO_SHIFT  (3)
+#define MCTP_HDR_TO_MASK   (1)
+#define MCTP_HDR_SEQ_SHIFT (4)
+#define MCTP_HDR_SEQ_MASK  (0x3)
+#define MCTP_HDR_TAG_SHIFT (0)
+#define MCTP_HDR_TAG_MASK  (0x7)
+
+#define MCTP_MESSAGE_TO_SRC	      true
+#define MCTP_MESSAGE_TO_DST	      false
+#define MCTP_MESSAGE_CAPTURE_OUTGOING true
+#define MCTP_MESSAGE_CAPTURE_INCOMING false
+
+/* Baseline Transmission Unit and packet size */
+#define MCTP_BTU	       64
+#define MCTP_PACKET_SIZE(unit) ((unit) + sizeof(struct mctp_hdr))
+#define MCTP_BODY_SIZE(unit)   ((unit) - sizeof(struct mctp_hdr))
+
+/* packet buffers */
+
+struct mctp_pktbuf {
+	size_t start, end, size;
+	size_t mctp_hdr_off;
+	struct mctp_pktbuf *next;
+	unsigned char data[];
+};
+
+struct mctp_binding;
+
+struct mctp_pktbuf *mctp_pktbuf_alloc(struct mctp_binding *hw, size_t len);
+void mctp_pktbuf_free(struct mctp_pktbuf *pkt);
+struct mctp_hdr *mctp_pktbuf_hdr(struct mctp_pktbuf *pkt);
+void *mctp_pktbuf_data(struct mctp_pktbuf *pkt);
+size_t mctp_pktbuf_size(struct mctp_pktbuf *pkt);
+void *mctp_pktbuf_alloc_start(struct mctp_pktbuf *pkt, size_t size);
+void *mctp_pktbuf_alloc_end(struct mctp_pktbuf *pkt, size_t size);
+int mctp_pktbuf_push(struct mctp_pktbuf *pkt, void *data, size_t len);
+void *mctp_pktbuf_pop(struct mctp_pktbuf *pkt, size_t len);
+
+/* MCTP core */
+struct mctp;
+struct mctp_bus;
+
+struct mctp *mctp_init(void);
+void mctp_set_max_message_size(struct mctp *mctp, size_t message_size);
+typedef void (*mctp_capture_fn)(struct mctp_pktbuf *pkt, bool outgoing,
+				void *user);
+void mctp_set_capture_handler(struct mctp *mctp, mctp_capture_fn fn,
+			      void *user);
+void mctp_destroy(struct mctp *mctp);
+
+/* Register a binding to the MCTP core, and creates a bus (populating
+ * binding->bus).
+ *
+ * If this function is called, the MCTP stack is initialised as an 'endpoint',
+ * and will deliver local packets to a RX callback - see `mctp_set_rx_all()`
+ * below.
+ */
+int mctp_register_bus(struct mctp *mctp, struct mctp_binding *binding,
+		      mctp_eid_t eid);
+
+void mctp_unregister_bus(struct mctp *mctp, struct mctp_binding *binding);
+
+/* Create a simple bidirectional bridge between busses.
+ *
+ * In this mode, the MCTP stack is initialised as a bridge. There is no EID
+ * defined, so no packets are considered local. Instead, all messages from one
+ * binding are forwarded to the other.
+ */
+int mctp_bridge_busses(struct mctp *mctp, struct mctp_binding *b1,
+		       struct mctp_binding *b2);
+
+typedef void (*mctp_rx_fn)(uint8_t src_eid, bool tag_owner, uint8_t msg_tag,
+			   void *data, void *msg, size_t len);
+
+int mctp_set_rx_all(struct mctp *mctp, mctp_rx_fn fn, void *data);
+
+int mctp_message_tx(struct mctp *mctp, mctp_eid_t eid, bool tag_owner,
+		    uint8_t msg_tag, void *msg, size_t msg_len);
+
+/* hardware bindings */
+
+/**
+ * @tx: Binding function to transmit one packet on the interface
+ *      Return:
+ *      * 0 - Success, pktbuf can be released
+ *	* -EMSGSIZE - Packet exceeds binding MTU, pktbuf must be dropped
+ *	* -EBUSY - Packet unable to be transmitted, pktbuf must be retained
+ */
+struct mctp_binding {
+	const char *name;
+	uint8_t version;
+	struct mctp_bus *bus;
+	struct mctp *mctp;
+	size_t pkt_size;
+	size_t pkt_header;
+	size_t pkt_trailer;
+	int (*start)(struct mctp_binding *binding);
+	int (*tx)(struct mctp_binding *binding, struct mctp_pktbuf *pkt);
+	mctp_rx_fn control_rx;
+	void *control_rx_data;
+};
+
+enum mctp_bus_state {
+        mctp_bus_state_constructed = 0,
+        mctp_bus_state_tx_enabled,
+        mctp_bus_state_tx_disabled,
+};
+
+void mctp_binding_set_tx_enabled(struct mctp_binding *binding, bool enable);
+
+
+enum mctp_bus_state mctp_bus_get_state(struct mctp_bus *bus);
+
+/*
+ * Receive a packet from binding to core. Takes ownership of pkt, free()-ing it
+ * after use.
+ */
+void mctp_bus_rx(struct mctp_binding *binding, struct mctp_pktbuf *pkt);
+
+/* environment-specific allocation */
+void mctp_set_alloc_ops(void *(*alloc)(size_t), void (*free)(void *),
+			void *(realloc)(void *, size_t));
+
+/* environment-specific logging */
+
+void mctp_set_log_stdio(int level);
+void mctp_set_log_syslog(void);
+void mctp_set_log_custom(void (*fn)(int, const char *, va_list));
+
+/* these should match the syslog-standard LOG_* definitions, for
+ * easier use with syslog */
+#define MCTP_LOG_ERR	 3
+#define MCTP_LOG_WARNING 4
+#define MCTP_LOG_NOTICE	 5
+#define MCTP_LOG_INFO	 6
+#define MCTP_LOG_DEBUG	 7
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* _LIBMCTP_H */
diff --git a/libmctp/log.c b/libmctp/log.c
new file mode 100644
index 00000000..cbdbbcaa
--- /dev/null
+++ b/libmctp/log.c
@@ -0,0 +1,75 @@
+/* SPDX-License-Identifier: Apache-2.0 OR GPL-2.0-or-later */
+
+#include <stdarg.h>
+
+#include "libmctp.h"
+#include "libmctp-log.h"
+
+#ifdef HAVE_CONFIG_H
+#include "config.h"
+#endif
+
+#ifdef MCTP_HAVE_STDIO
+#include <stdio.h>
+#endif
+
+#ifdef MCTP_HAVE_SYSLOG
+#include <syslog.h>
+#endif
+
+enum {
+	MCTP_LOG_NONE,
+	MCTP_LOG_STDIO,
+	MCTP_LOG_SYSLOG,
+	MCTP_LOG_CUSTOM,
+} log_type = MCTP_LOG_NONE;
+
+static int log_stdio_level;
+static void (*log_custom_fn)(int, const char *, va_list);
+
+void mctp_prlog(int level, const char *fmt, ...)
+{
+	va_list ap;
+
+	va_start(ap, fmt);
+
+	switch (log_type) {
+	case MCTP_LOG_NONE:
+		break;
+	case MCTP_LOG_STDIO:
+#ifdef MCTP_HAVE_STDIO
+		if (level <= log_stdio_level) {
+			vfprintf(stderr, fmt, ap);
+			fputs("\n", stderr);
+		}
+#endif
+		break;
+	case MCTP_LOG_SYSLOG:
+#ifdef MCTP_HAVE_SYSLOG
+		vsyslog(level, fmt, ap);
+#endif
+		break;
+	case MCTP_LOG_CUSTOM:
+		log_custom_fn(level, fmt, ap);
+		break;
+	}
+
+	va_end(ap);
+}
+
+void mctp_set_log_stdio(int level)
+{
+	log_type = MCTP_LOG_STDIO;
+	log_stdio_level = level;
+}
+
+void mctp_set_log_syslog(void)
+{
+	log_type = MCTP_LOG_SYSLOG;
+}
+
+void mctp_set_log_custom(void (*fn)(int, const char *, va_list))
+{
+	log_type = MCTP_LOG_CUSTOM;
+	log_custom_fn = fn;
+}
diff --git a/libmctp/range.h b/libmctp/range.h
new file mode 100644
index 00000000..20349f24
--- /dev/null
+++ b/libmctp/range.h
@@ -0,0 +1,26 @@
+#ifndef _RANGE_H
+#define _RANGE_H
+
+#ifndef typeof
+#define typeof __typeof__
+#endif
+
+#ifndef MIN
+#define MIN(a, b)                                                              \
+	({                                                                     \
+		typeof(a) _a = a;                                              \
+		typeof(b) _b = b;                                              \
+		_a < _b ? _a : _b;                                             \
+	})
+#endif
+
+#ifndef MAX
+#define MAX(a, b)                                                              \
+	({                                                                     \
+		typeof(a) _a = a;                                              \
+		typeof(b) _b = b;                                              \
+		_a > _b ? _a : _b;                                             \
+	})
+#endif
+
+#endif
diff --git a/libmctp/serial.c b/libmctp/serial.c
new file mode 100644
index 00000000..22517a76
--- /dev/null
+++ b/libmctp/serial.c
@@ -0,0 +1,383 @@
+/* SPDX-License-Identifier: Apache-2.0 OR GPL-2.0-or-later */
+
+#include <assert.h>
+#include <errno.h>
+#include <stdbool.h>
+#include <stdlib.h>
+#include <string.h>
+
+#ifdef HAVE_CONFIG_H
+#include "config.h"
+#endif
+
+#ifdef MCTP_HAVE_FILEIO
+#include <fcntl.h>
+#include <poll.h>
+#include <unistd.h>
+#else
+static const size_t write(int fd, void *buf, size_t len)
+{
+	return -1;
+}
+#endif
+
+#define pr_fmt(x) "serial: " x
+
+/*
+ * @fn: A function that will copy data from the buffer at src into the dst object
+ * @dst: An opaque object to pass as state to fn
+ * @src: A pointer to the buffer of data to copy to dst
+ * @len: The length of the data pointed to by src
+ * @return: 0 on succes, negative error code on failure
+ *
+ * Pre-condition: fn returns a write count or a negative error code
+ * Post-condition: All bytes written or an error has occurred
+ */
+#define mctp_write_all(fn, dst, src, len)                                      \
+	({                                                                     \
+		typeof(src) __src = src;                                       \
+		ssize_t wrote;                                                 \
+		while (len) {                                                  \
+			wrote = fn(dst, __src, len);                           \
+			if (wrote < 0)                                         \
+				break;                                         \
+			__src += wrote;                                        \
+			len -= wrote;                                          \
+		}                                                              \
+		len ? wrote : 0;                                               \
+	})
+
+static ssize_t mctp_serial_write(int fildes, const void *buf, size_t nbyte)
+{
+	ssize_t wrote;
+
+	return ((wrote = write(fildes, buf, nbyte)) < 0) ? -errno : wrote;
+}
+
+#include "libmctp.h"
+#include "libmctp-alloc.h"
+#include "libmctp-log.h"
+#include "libmctp-serial.h"
+#include "container_of.h"
+
+struct mctp_binding_serial {
+	struct mctp_binding binding;
+	int fd;
+	unsigned long bus_id;
+
+	mctp_serial_tx_fn tx_fn;
+	void *tx_fn_data;
+
+	/* receive buffer and state */
+	uint8_t rxbuf[1024];
+	struct mctp_pktbuf *rx_pkt;
+	uint8_t rx_exp_len;
+	uint16_t rx_fcs;
+	enum {
+		STATE_WAIT_SYNC_START,
+		STATE_WAIT_REVISION,
+		STATE_WAIT_LEN,
+		STATE_DATA,
+		STATE_DATA_ESCAPED,
+		STATE_WAIT_FCS1,
+		STATE_WAIT_FCS2,
+		STATE_WAIT_SYNC_END,
+	} rx_state;
+
+	/* temporary transmit buffer */
+	uint8_t txbuf[256];
+};
+
+#define binding_to_serial(b)                                                   \
+	container_of(b, struct mctp_binding_serial, binding)
+
+#define MCTP_SERIAL_REVISION	 0x01
+#define MCTP_SERIAL_FRAMING_FLAG 0x7e
+#define MCTP_SERIAL_ESCAPE	 0x7d
+
+struct mctp_serial_header {
+	uint8_t flag;
+	uint8_t revision;
+	uint8_t len;
+};
+
+struct mctp_serial_trailer {
+	uint8_t fcs_msb;
+	uint8_t fcs_lsb;
+	uint8_t flag;
+};
+
+static size_t mctp_serial_pkt_escape(struct mctp_pktbuf *pkt, uint8_t *buf)
+{
+	uint8_t total_len;
+	uint8_t *p;
+	int i, j;
+
+	total_len = pkt->end - pkt->mctp_hdr_off;
+
+	p = (void *)mctp_pktbuf_hdr(pkt);
+
+	for (i = 0, j = 0; i < total_len; i++, j++) {
+		uint8_t c = p[i];
+		if (c == 0x7e || c == 0x7d) {
+			if (buf)
+				buf[j] = 0x7d;
+			j++;
+			c ^= 0x20;
+		}
+		if (buf)
+			buf[j] = c;
+	}
+
+	return j;
+}
+
+static int mctp_binding_serial_tx(struct mctp_binding *b,
+				  struct mctp_pktbuf *pkt)
+{
+	struct mctp_binding_serial *serial = binding_to_serial(b);
+	struct mctp_serial_header *hdr;
+	struct mctp_serial_trailer *tlr;
+	uint8_t *buf;
+	size_t len;
+
+	/* the length field in the header excludes serial framing
+	 * and escape sequences */
+	len = mctp_pktbuf_size(pkt);
+
+	hdr = (void *)serial->txbuf;
+	hdr->flag = MCTP_SERIAL_FRAMING_FLAG;
+	hdr->revision = MCTP_SERIAL_REVISION;
+	hdr->len = len;
+
+	buf = (void *)(hdr + 1);
+
+	len = mctp_serial_pkt_escape(pkt, NULL);
+	if (len + sizeof(*hdr) + sizeof(*tlr) > sizeof(serial->txbuf))
+		return -EMSGSIZE;
+
+	mctp_serial_pkt_escape(pkt, buf);
+
+	buf += len;
+
+	tlr = (void *)buf;
+	tlr->flag = MCTP_SERIAL_FRAMING_FLAG;
+	/* todo: trailer FCS */
+	tlr->fcs_msb = 0;
+	tlr->fcs_lsb = 0;
+
+	len += sizeof(*hdr) + sizeof(*tlr);
+
+	if (!serial->tx_fn)
+		return mctp_write_all(mctp_serial_write, serial->fd,
+				      &serial->txbuf[0], len);
+
+	return mctp_write_all(serial->tx_fn, serial->tx_fn_data,
+			      &serial->txbuf[0], len);
+}
+
+static void mctp_serial_finish_packet(struct mctp_binding_serial *serial,
+				      bool valid)
+{
+	struct mctp_pktbuf *pkt = serial->rx_pkt;
+	assert(pkt);
+
+	if (valid)
+		mctp_bus_rx(&serial->binding, pkt);
+
+	serial->rx_pkt = NULL;
+}
+
+static void mctp_serial_start_packet(struct mctp_binding_serial *serial,
+				     uint8_t len)
+{
+	serial->rx_pkt = mctp_pktbuf_alloc(&serial->binding, len);
+}
+
+static void mctp_rx_consume_one(struct mctp_binding_serial *serial, uint8_t c)
+{
+	struct mctp_pktbuf *pkt = serial->rx_pkt;
+
+	mctp_prdebug("state: %d, char 0x%02x", serial->rx_state, c);
+
+	assert(!pkt == (serial->rx_state == STATE_WAIT_SYNC_START ||
+			serial->rx_state == STATE_WAIT_REVISION ||
+			serial->rx_state == STATE_WAIT_LEN));
+
+	switch (serial->rx_state) {
+	case STATE_WAIT_SYNC_START:
+		if (c != MCTP_SERIAL_FRAMING_FLAG) {
+			mctp_prdebug("lost sync, dropping packet");
+			if (pkt)
+				mctp_serial_finish_packet(serial, false);
+		} else {
+			serial->rx_state = STATE_WAIT_REVISION;
+		}
+		break;
+
+	case STATE_WAIT_REVISION:
+		if (c == MCTP_SERIAL_REVISION) {
+			serial->rx_state = STATE_WAIT_LEN;
+		} else {
+			mctp_prdebug("invalid revision 0x%02x", c);
+			serial->rx_state = STATE_WAIT_SYNC_START;
+		}
+		break;
+	case STATE_WAIT_LEN:
+		if (c > serial->binding.pkt_size ||
+		    c < sizeof(struct mctp_hdr)) {
+			mctp_prdebug("invalid size %d", c);
+			serial->rx_state = STATE_WAIT_SYNC_START;
+		} else {
+			mctp_serial_start_packet(serial, 0);
+			pkt = serial->rx_pkt;
+			serial->rx_exp_len = c;
+			serial->rx_state = STATE_DATA;
+		}
+		break;
+
+	case STATE_DATA:
+		if (c == MCTP_SERIAL_ESCAPE) {
+			serial->rx_state = STATE_DATA_ESCAPED;
+		} else {
+			mctp_pktbuf_push(pkt, &c, 1);
+			if (pkt->end - pkt->mctp_hdr_off == serial->rx_exp_len)
+				serial->rx_state = STATE_WAIT_FCS1;
+		}
+		break;
+
+	case STATE_DATA_ESCAPED:
+		c ^= 0x20;
+		mctp_pktbuf_push(pkt, &c, 1);
+		if (pkt->end - pkt->mctp_hdr_off == serial->rx_exp_len)
+			serial->rx_state = STATE_WAIT_FCS1;
+		else
+			serial->rx_state = STATE_DATA;
+		break;
+
+	case STATE_WAIT_FCS1:
+		serial->rx_fcs = c << 8;
+		serial->rx_state = STATE_WAIT_FCS2;
+		break;
+	case STATE_WAIT_FCS2:
+		serial->rx_fcs |= c;
+		/* todo: check fcs */
+		serial->rx_state = STATE_WAIT_SYNC_END;
+		break;
+
+	case STATE_WAIT_SYNC_END:
+		if (c == MCTP_SERIAL_FRAMING_FLAG) {
+			mctp_serial_finish_packet(serial, true);
+		} else {
+			mctp_prdebug("missing end frame marker");
+			mctp_serial_finish_packet(serial, false);
+		}
+		serial->rx_state = STATE_WAIT_SYNC_START;
+		break;
+	}
+
+	mctp_prdebug(" -> state: %d", serial->rx_state);
+}
+static void mctp_rx_consume(struct mctp_binding_serial *serial, const void *buf,
+			    size_t len)
+{
+	size_t i;
+
+	for (i = 0; i < len; i++)
+		mctp_rx_consume_one(serial, *(uint8_t *)(buf + i));
+}
+
+#ifdef MCTP_HAVE_FILEIO
+int mctp_serial_read(struct mctp_binding_serial *serial)
+{
+	ssize_t len;
+
+	len = read(serial->fd, serial->rxbuf, sizeof(serial->rxbuf));
+	if (len == 0)
+		return -1;
+
+	if (len < 0) {
+		mctp_prerr("can't read from serial device: %m");
+		return -1;
+	}
+
+	mctp_rx_consume(serial, serial->rxbuf, len);
+
+	return 0;
+}
+
+int mctp_serial_init_pollfd(struct mctp_binding_serial *serial,
+			    struct pollfd *pollfd)
+{
+	pollfd->fd = serial->fd;
+	pollfd->events = POLLIN;
+
+	return 0;
+}
+
+int mctp_serial_open_path(struct mctp_binding_serial *serial,
+			  const char *device)
+{
+	serial->fd = open(device, O_RDWR);
+	if (serial->fd < 0)
+		mctp_prerr("can't open device %s: %m", device);
+
+	return 0;
+}
+
+void mctp_serial_open_fd(struct mctp_binding_serial *serial, int fd)
+{
+	serial->fd = fd;
+}
+#endif
+
+void mctp_serial_set_tx_fn(struct mctp_binding_serial *serial,
+			   mctp_serial_tx_fn fn, void *data)
+{
+	serial->tx_fn = fn;
+	serial->tx_fn_data = data;
+}
+
+int mctp_serial_rx(struct mctp_binding_serial *serial, const void *buf,
+		   size_t len)
+{
+	mctp_rx_consume(serial, buf, len);
+	return 0;
+}
+
+static int mctp_serial_core_start(struct mctp_binding *binding)
+{
+	mctp_binding_set_tx_enabled(binding, true);
+	return 0;
+}
+
+struct mctp_binding *mctp_binding_serial_core(struct mctp_binding_serial *b)
+{
+	return &b->binding;
+}
+
+struct mctp_binding_serial *mctp_serial_init(void)
+{
+	struct mctp_binding_serial *serial;
+
+	serial = __mctp_alloc(sizeof(*serial));
+	memset(serial, 0, sizeof(*serial));
+	serial->fd = -1;
+	serial->rx_state = STATE_WAIT_SYNC_START;
+	serial->rx_pkt = NULL;
+	serial->binding.name = "serial";
+	serial->binding.version = 1;
+	serial->binding.pkt_size = MCTP_PACKET_SIZE(MCTP_BTU);
+	serial->binding.pkt_header = 0;
+	serial->binding.pkt_header = 0;
+
+	serial->binding.start = mctp_serial_core_start;
+	serial->binding.tx = mctp_binding_serial_tx;
+
+	return serial;
+}
+
+void mctp_serial_destroy(struct mctp_binding_serial *serial)
+{
+	__mctp_free(serial);
+}
