mctp: Add mctp subsystem with uart binding

libmctp provides interfaces for wiring up a MCTP bus it calls bus
bindings. The bindings provided in libmctp however are not directly
useful to Zephyr without some work. Provide an initial uart binding that
directly uses Zephyr's async uart interface.

Signed-off-by: Tom Burdick <[email protected]>

Author: teburd

include/zephyr/mctp/mctp_uart.h

@@ -0,0 +1,86 @@
+/*
+ * Copyright (c) 2024 Intel Corporation
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ *
+ */
+
+#ifndef ZEPHYR_MCTP_UART_H_
+#define ZEPHYR_MCTP_UART_H_
+
+#include <stdint.h>
+#include <zephyr/kernel.h>
+#include <zephyr/device.h>
+#include <libmctp.h>
+
+/**
+ * @brief An MCTP binding for Zephyr's asynchronous UART interface
+ */
+struct mctp_binding_uart {
+	/** @cond INTERNAL_HIDDEN */
+	struct mctp_binding binding;
+	const struct device *dev;
+
+	/* receive buffers and state */
+	uint8_t rx_buf[2][256];
+	bool rx_buf_used[2];
+	struct mctp_pktbuf *rx_pkt;
+	uint8_t rx_exp_len;
+	uint16_t rx_fcs;
+	uint16_t rx_fcs_calc;
+	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;
+	int rx_res;
+
+	/* staging buffer for tx */
+	uint8_t tx_buf[256];
+	int tx_res;
+
+	/** @endcond INTERNAL_HIDDEN */
+};
+
+/**
+ * @brief Start the receive of a single mctp message
+ *
+ * Will read a single mctp message from the uart.
+ *
+ * @param uart MCTP UART binding
+ */
+void mctp_uart_start_rx(struct mctp_binding_uart *uart);
+
+/** @cond INTERNAL_HIDDEN */
+int mctp_uart_start(struct mctp_binding *binding);
+int mctp_uart_tx(struct mctp_binding *binding, struct mctp_pktbuf *pkt);
+/** @endcond INTERNAL_HIDDEN */
+
+/**
+ * @brief Statically define a MCTP bus binding for a UART
+ *
+ * @param _name Symbolic name of the bus binding variable
+ * @param _dev UART device
+ */
+#define MCTP_UART_DT_DEFINE(_name, _dev)                                                           \
+	struct mctp_binding_uart _name = {                                                         \
+		.binding =                                                                         \
+			{                                                                          \
+				.name = STRINGIFY(_name), .version = 1,                            \
+						  .pkt_size = MCTP_PACKET_SIZE(MCTP_BTU),          \
+						  .pkt_header = 0, .pkt_trailer = 0,               \
+						  .start = mctp_uart_start, .tx = mctp_uart_tx,    \
+				},                                                                 \
+				.dev = _dev,                                                       \
+				.rx_state = STATE_WAIT_SYNC_START,                                 \
+				.rx_pkt = NULL,                                                    \
+				.rx_res = 0,                                                       \
+				.tx_res = 0,                                                       \
+	};
+
+#endif /* ZEPHYR_MCTP_UART_H_ */

subsys/CMakeLists.txt

@@ -46,6 +46,7 @@ add_subdirectory_ifdef(CONFIG_IMG_MANAGER dfu)
 add_subdirectory_ifdef(CONFIG_INPUT input)
 add_subdirectory_ifdef(CONFIG_JWT jwt)
 add_subdirectory_ifdef(CONFIG_LLEXT llext)
+add_subdirectory_ifdef(CONFIG_MCTP mctp)
 add_subdirectory_ifdef(CONFIG_MODEM_MODULES modem)
 add_subdirectory_ifdef(CONFIG_NETWORKING net)
 add_subdirectory_ifdef(CONFIG_PROFILING profiling)

subsys/Kconfig

@@ -26,6 +26,7 @@ source "subsys/jwt/Kconfig"
 source "subsys/llext/Kconfig"
 source "subsys/logging/Kconfig"
 source "subsys/lorawan/Kconfig"
+source "subsys/mctp/Kconfig"
 source "subsys/mem_mgmt/Kconfig"
 source "subsys/mgmt/Kconfig"
 source "subsys/modbus/Kconfig"

subsys/mctp/CMakeLists.txt

@@ -0,0 +1,2 @@
+zephyr_library()
+zephyr_library_sources_ifdef(CONFIG_MCTP_UART mctp_uart.c)

subsys/mctp/Kconfig

@@ -0,0 +1,22 @@
+# Copyright (c) 2024 Intel Corporation
+# SPDX-License-Identifier: Apache-2.0
+
+menuconfig MCTP
+	bool "Management Component Transport Protocol"
+	help
+	  Enable the MCTP Subsystem and Module Usage
+
+if MCTP
+
+config MCTP_UART
+	bool "MCTP UART Binding"
+	depends on UART_ASYNC_API
+	help
+	  Build the MCTP UART binding to use MCTP over Zephyr's async UART
+	  interface.
+
+module = MCTP
+module-str = MCTP
+source "subsys/logging/Kconfig.template.log_config"
+
+endif