jtag/drivers/cmsis_dap: add new backend cmsis_dap_tcp

Create a new backend for cmsis_dap driver that allows CMSIS-DAP protocol to run over TCP/IP instead of USB. An example implementation of the firmware for an SWD programmer that uses this cmsis_dap_tcp protocol can be found at the link below. https://github.com/bkuschak/cmsis_dap_tcp_esp32 Using this cmsis_dap_tcp backend with the firmware above on an ESP32-C6 programmer and STM32F401RE target shows the following performance: - loading 96KB image to RAM: 80 KB/sec - dumping 96KB image from RAM: 72 KB/sec - flashing 512KB image completes in about 13.5 seconds (including erase, program, and verify). Change-Id: I6e3e45016bd16ef2259561b1046788f5536b0687 Signed-off-by: Brian Kuschak <bkuschak@gmail.com> Reviewed-on: https://review.openocd.org/c/openocd/+/8973 Reviewed-by: Tomas Vanek <vanekt@fbl.cz> Reviewed-by: Antonio Borneo <borneo.antonio@gmail.com> Tested-by: jenkins
2025-10-14 02:58:23 +08:00 · 2025-06-11 12:41:04 +08:00
parent 64ed1c74d5
commit fcff4b712c
8 changed files with 543 additions and 11 deletions
--- a/configure.ac
+++ b/configure.ac
@@ -204,6 +204,9 @@ m4_define([RSHIM_ADAPTER],
 m4_define([AMTJTAGACCEL_ADAPTER],
 	[[[amtjtagaccel], [Amontec JTAG-Accelerator driver], [AMTJTAGACCEL]]])

+m4_define([CMSIS_DAP_TCP_ADAPTER],
+	[[[cmsis_dap_tcp], [CMSIS-DAP v2 compliant dongle (TCP)], [CMSIS_DAP_TCP]]])
+
 m4_define([HOST_ARM_BITBANG_ADAPTERS],
 	[[[ep93xx], [Bitbanging on EP93xx-based SBCs], [EP93XX]],
 	[[at91rm9200], [Bitbanging on AT91RM9200-based SBCs], [AT91RM9200]]])
@@ -327,7 +330,8 @@ AC_ARG_ADAPTERS([
  JTAG_VPI_ADAPTER,
  RSHIM_ADAPTER,
  XVC_ADAPTERS,
-  LIBJAYLINK_ADAPTERS
+  LIBJAYLINK_ADAPTERS,
+  CMSIS_DAP_TCP_ADAPTER
  ],[auto])

 AC_ARG_ADAPTERS([
@@ -623,6 +627,7 @@ PROCESS_ADAPTERS([LIBGPIOD_ADAPTERS], ["x$use_libgpiod" = "xyes"], [Linux libgpi
 PROCESS_ADAPTERS([DMEM_ADAPTER], ["x$is_linux" = "xyes"], [Linux /dev/mem])
 PROCESS_ADAPTERS([SYSFSGPIO_ADAPTER], ["x$is_linux" = "xyes"], [Linux sysfs])
 PROCESS_ADAPTERS([REMOTE_BITBANG_ADAPTER], [true], [unused])
+PROCESS_ADAPTERS([CMSIS_DAP_TCP_ADAPTER], [true], [unused])
 PROCESS_ADAPTERS([LIBJAYLINK_ADAPTERS], ["x$use_internal_libjaylink" = "xyes" -o "x$use_libjaylink" = "xyes"], [libjaylink-0.2])
 PROCESS_ADAPTERS([XVC_ADAPTERS], ["x$is_linux" = "xyes" -a "x$ac_cv_header_linux_pci_h" = "xyes"], [Linux build])
 PROCESS_ADAPTERS([SERIAL_PORT_ADAPTERS], ["x$can_build_buspirate" = "xyes"],
@@ -682,6 +687,8 @@ AS_IF([test "x$enable_stlink" != "xno" -o "x$enable_ti_icdi" != "xno" -o "x$enab
 AM_CONDITIONAL([HLADAPTER_STLINK], [test "x$enable_stlink" != "xno"])
 AM_CONDITIONAL([HLADAPTER_ICDI], [test "x$enable_ti_icdi" != "xno"])
 AM_CONDITIONAL([HLADAPTER_NULINK], [test "x$enable_nulink" != "xno"])
+AM_CONDITIONAL([CMSIS_DAP_CORE],
+   [test "x$enable_cmsis_dap" != "xno" -o "x$enable_cmsis_dap_v2" != "xno" -o "x$enable_cmsis_dap_tcp" != "xno"])

 AS_IF([test "x$enable_jlink" != "xno"], [
  AS_IF([test "x$use_internal_libjaylink" = "xyes"], [
@@ -832,6 +839,7 @@ m4_foreach([adapterTuple], [USB1_ADAPTERS,
 	AMTJTAGACCEL_ADAPTER,
 	HOST_ARM_BITBANG_ADAPTERS,
 	HOST_ARM_OR_AARCH64_BITBANG_ADAPTERS,
+	CMSIS_DAP_TCP_ADAPTER,
 	DUMMY_ADAPTER,
 	OPTIONAL_LIBRARIES,
 	COVERAGE],
--- a/doc/openocd.texi
+++ b/doc/openocd.texi
@@ -2621,7 +2621,7 @@ ch347 activity_led n4

@deffn {Interface Driver} {cmsis-dap}
 ARM CMSIS-DAP compliant based adapter v1 (USB HID based)
-or v2 (USB bulk).
+or v2 (USB bulk or TCP/IP).

@deffn {Config Command} {cmsis-dap vid_pid} [vid pid]+
 The vendor ID and product ID of the CMSIS-DAP device. If not specified
@@ -2632,14 +2632,17 @@ cmsis-dap vid_pid 0xc251 0xf001 0x0d28 0x0204
@end example
@end deffn

-@deffn {Config Command} {cmsis-dap backend} [@option{auto}|@option{usb_bulk}|@option{hid}]
+@deffn {Config Command} {cmsis-dap backend} [@option{auto}|@option{usb_bulk}|@option{hid}|@option{tcp}]
 Specifies how to communicate with the adapter:

@itemize @minus
-@item @option{hid} Use HID generic reports - CMSIS-DAP v1
+@item @option{hid} Use USB HID generic reports - CMSIS-DAP v1
@item @option{usb_bulk} Use USB bulk - CMSIS-DAP v2
-@item @option{auto} First try USB bulk CMSIS-DAP v2, if not found try HID CMSIS-DAP v1.
-This is the default if @command{cmsis-dap backend} is not specified.
+@item @option{tcp} Use TCP/IP instead of USB
+@item @option{auto} First try USB bulk CMSIS-DAP v2, if not found try USB HID
+CMSIS-DAP v1, if not found try TCP (if @command{cmsis-dap tcp host} is
+configured). This is the default if @command{cmsis-dap backend} is not
+specified.
@end itemize
@end deffn

@@ -2649,6 +2652,36 @@ In most cases need not to be specified and interfaces are searched by
 interface string or for user class interface.
@end deffn

+@deffn {Config Command} {cmsis-dap tcp host} hostname
+Specifies the @var{hostname} or IP address of the remote programmer. For use
+with 'tcp' backend only.
+@example
+cmsis-dap backend tcp
+cmsis-dap tcp host 192.168.1.4
+@end example
+@end deffn
+
+@deffn {Config Command} {cmsis-dap tcp port} port
+Specifies the TCP @var{port} number used by the remote programmer for DAP
+commands. The default port is 4441. For use with 'tcp' backend only.
+@example
+cmsis-dap backend tcp
+cmsis-dap tcp host 192.168.1.4
+cmsis-dap tcp port 4441
+@end example
+@end deffn
+
+@deffn {Config Command} {cmsis-dap tcp min_timeout} milliseconds
+Sets a lower bound on the requested timeout in @var{milliseconds} to wait for
+response packets from the remote programmer when using the 'tcp' backend. The
+user may want to use a larger value on slower networks, to avoid getting
+command mismatch errors. Default value is 150 milliseconds. For use with 'tcp'
+backend only.
+@example
+cmsis-dap tcp min_timeout 200
+@end example
+@end deffn
+
@deffn {Command} {cmsis-dap quirk} [@option{enable}|@option{disable}]
 Enables or disables the following workarounds of known CMSIS-DAP adapter
 quirks:
--- a/src/helper/replacements.h
+++ b/src/helper/replacements.h
@@ -225,6 +225,20 @@ static inline int socket_select(int max_fd,
 #endif
 }

+static inline int socket_recv_timeout(int fd, unsigned long timeout_msec)
+{
+#ifdef _WIN32
+	DWORD timeout = timeout_msec;
+	return setsockopt(fd, SOL_SOCKET, SO_RCVTIMEO, (const char *)&timeout,
+			sizeof(timeout));
+#else
+	struct timeval tv;
+	tv.tv_sec = timeout_msec / 1000;
+	tv.tv_usec = (timeout_msec % 1000) * 1000;
+	return setsockopt(fd, SOL_SOCKET, SO_RCVTIMEO, (const char *)&tv, sizeof(tv));
+#endif
+}
+
 #ifndef HAVE_ELF_H

 typedef uint32_t Elf32_Addr;
--- a/src/jtag/drivers/Makefile.am
+++ b/src/jtag/drivers/Makefile.am
@@ -186,15 +186,17 @@ endif
 if OPENJTAG
 DRIVERFILES += %D%/openjtag.c
 endif
+if CMSIS_DAP_CORE
+DRIVERFILES += %D%/cmsis_dap.c
+endif
 if CMSIS_DAP_HID
 DRIVERFILES += %D%/cmsis_dap_usb_hid.c
-DRIVERFILES += %D%/cmsis_dap.c
 endif
 if CMSIS_DAP_USB
 DRIVERFILES += %D%/cmsis_dap_usb_bulk.c
-if !CMSIS_DAP_HID
-DRIVERFILES += %D%/cmsis_dap.c
 endif
+if CMSIS_DAP_TCP
+DRIVERFILES += %D%/cmsis_dap_tcp.c
 endif
 if IMX_GPIO
 DRIVERFILES += %D%/imx_gpio.c
--- a/src/jtag/drivers/cmsis_dap.c
+++ b/src/jtag/drivers/cmsis_dap.c
@@ -52,9 +52,16 @@ const struct cmsis_dap_backend cmsis_dap_hid_backend = {
 };
 #endif

+#if BUILD_CMSIS_DAP_TCP == 0
+const struct cmsis_dap_backend cmsis_dap_tcp_backend = {
+	.name = "tcp"
+};
+#endif
+
 static const struct cmsis_dap_backend *const cmsis_dap_backends[] = {
 	&cmsis_dap_usb_backend,
 	&cmsis_dap_hid_backend,
+	&cmsis_dap_tcp_backend,
 };

 /* USB Config */
@@ -2275,8 +2282,8 @@ static const struct command_registration cmsis_dap_subcommand_handlers[] = {
 		.name = "backend",
 		.handler = &cmsis_dap_handle_backend_command,
 		.mode = COMMAND_CONFIG,
-		.help = "set the communication backend to use (USB bulk or HID).",
-		.usage = "(auto | usb_bulk | hid)",
+		.help = "set the communication backend to use (USB bulk or HID, or TCP).",
+		.usage = "(auto | usb_bulk | hid | tcp)",
 	},
 	{
 		.name = "quirk",
@@ -2293,6 +2300,15 @@ static const struct command_registration cmsis_dap_subcommand_handlers[] = {
 		.help = "USB bulk backend-specific commands",
 		.usage = "<cmd>",
 	},
+#endif
+#if BUILD_CMSIS_DAP_TCP
+	{
+		.name = "tcp",
+		.chain = cmsis_dap_tcp_subcommand_handlers,
+		.mode = COMMAND_ANY,
+		.help = "TCP backend-specific commands",
+		.usage = "<cmd>",
+	},
 #endif
 	COMMAND_REGISTRATION_DONE
 };
--- a/src/jtag/drivers/cmsis_dap.h
+++ b/src/jtag/drivers/cmsis_dap.h
@@ -77,7 +77,9 @@ struct cmsis_dap_backend {

 extern const struct cmsis_dap_backend cmsis_dap_hid_backend;
 extern const struct cmsis_dap_backend cmsis_dap_usb_backend;
+extern const struct cmsis_dap_backend cmsis_dap_tcp_backend;
 extern const struct command_registration cmsis_dap_usb_subcommand_handlers[];
+extern const struct command_registration cmsis_dap_tcp_subcommand_handlers[];

 #define REPORT_ID_SIZE   1

--- a/src/jtag/drivers/cmsis_dap_tcp.c
+++ b/src/jtag/drivers/cmsis_dap_tcp.c
@@ -0,0 +1,439 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+/***************************************************************************
+ *	 Provides CMSIS-DAP protocol over a TCP/IP socket.					   *
+ *	 UART and SWO are currently unsupported.							   *
+ *																		   *
+ *	 Copyright (C) 2025 by Brian Kuschak <bkuschak@gmail.com>			   *
+ *																		   *
+ *	 Adapted from cmsis_dap_usb_hid.c. Copyright (C) 2013-2018 by:		   *
+ *	   Mickaël Thomas <mickael9@gmail.com>								   *
+ *	   Maksym Hilliaka <oter@frozen-team.com>							   *
+ *	   Phillip Pearson <pp@myelin.co.nz>								   *
+ *	   Paul Fertser <fercerpav@gmail.com>								   *
+ *	   mike brown <mike@theshedworks.org.uk>							   *
+ *	   Spencer Oliver <spen@spen-soft.co.uk>							   *
+ *																		   *
+ ***************************************************************************/
+
+#ifdef HAVE_CONFIG_H
+#include "config.h"
+#endif
+
+#include <hidapi.h>
+#ifdef HAVE_NETDB_H
+#include <netdb.h>
+#endif
+#ifdef HAVE_NETINET_TCP_H
+#include <netinet/tcp.h>
+#endif
+#include <stdbool.h>
+#include <string.h>
+#ifdef HAVE_SYS_SOCKET_H
+#include <sys/socket.h>
+#endif
+#include <sys/types.h>
+
+#include "helper/command.h"
+#include "helper/log.h"
+#include "helper/replacements.h"
+#include "helper/system.h"
+#include "cmsis_dap.h"
+
+#define STRINGIFY(x) #x
+
+// If the protocol changes in the future, the SIGNATURE should also be changed.
+#define DAP_PKT_HDR_SIGNATURE	0x00504144	// "DAP"
+#define DAP_PKT_TYPE_REQUEST	0x01
+#define DAP_PKT_TYPE_RESPONSE	0x02
+
+#define CMSIS_DAP_TCP_PORT		4441		// Default. Can be overridden.
+#define CMSIS_DAP_PACKET_SIZE	1024		// Max payload size not including
+											// header.
+
+/* When flushing after an error, the CMSIS-DAP driver assumes the pipeline is
+ * empty if it doesn't get a response after a short 10 msec timeout. While this
+ * works for USB, it may not work for TCP/IP due to higher network latency. TCP
+ * response packets may take longer to arrive. We set a lower bound on timeout
+ * for blocking reads, to give enough time for packets to arrive.
+ *
+ * The user may override this default value by setting the parameter
+ * 'cmsis-dap tcp min_timeout'
+ */
+#define DEFAULT_MIN_TIMEOUT_MS	150
+
+/* CMSIS-DAP requests are variable length. With CMSIS-DAP over USB, the
+ * transfer sizes are preserved by the USB stack. However, TCP/IP is stream
+ * oriented so we perform our own packetization to preserve the boundaries
+ * between each request. This short header is prepended to each CMSIS-DAP
+ * request and response before being sent over the socket. Little endian format
+ * is used for multibyte values.
+ */
+struct __attribute__((packed)) cmsis_dap_tcp_packet_hdr {
+	uint32_t signature;		// "DAP"
+	uint16_t length;		// Not including header length.
+	uint8_t packet_type;
+	uint8_t reserved;		// Reserved for future use.
+};
+
+/* Defines for struct cmsis_dap_tcp_packet_hdr requested by reviewer. */
+#define HEADER_SIGNATURE_OFFSET		0
+#define HEADER_LENGTH_OFFSET		sizeof(uint32_t)
+#define HEADER_PACKET_TYPE_OFFSET	(sizeof(uint32_t) + sizeof(uint16_t))
+#define HEADER_RESERVED_OFFSET		(sizeof(uint32_t) + sizeof(uint16_t) + \
+									 sizeof(uint8_t))
+#define HEADER_SIZE					(sizeof(uint32_t) + sizeof(uint16_t) + \
+									 2 * sizeof(uint8_t))
+
+struct cmsis_dap_backend_data {
+	int sockfd;
+};
+
+static char *cmsis_dap_tcp_host;
+static char *const cmsis_dap_tcp_port_default = STRINGIFY(CMSIS_DAP_TCP_PORT);
+static char *cmsis_dap_tcp_port = cmsis_dap_tcp_port_default;
+static int cmsis_dap_tcp_min_timeout_ms = DEFAULT_MIN_TIMEOUT_MS;
+
+static void cmsis_dap_tcp_close(struct cmsis_dap *dap);
+static int cmsis_dap_tcp_alloc(struct cmsis_dap *dap, unsigned int pkt_sz);
+static void cmsis_dap_tcp_free(struct cmsis_dap *dap);
+
+static int cmsis_dap_tcp_open(struct cmsis_dap *dap,
+		uint16_t vids[] __attribute__((unused)),
+		uint16_t pids[] __attribute__((unused)),
+		const char *serial __attribute__((unused)))
+{
+	// Skip the open if the user has not provided a hostname.
+	if (!cmsis_dap_tcp_host) {
+		LOG_DEBUG("No TCP hostname, skipping open.");
+		return ERROR_FAIL;
+	}
+
+	// Ignore vids, pids, serial. We use host and port subcommands instead.
+
+	dap->bdata = malloc(sizeof(struct cmsis_dap_backend_data));
+	if (!dap->bdata) {
+		LOG_ERROR("CMSIS-DAP: unable to allocate memory");
+		return ERROR_FAIL;
+	}
+
+	struct addrinfo hints = {
+		.ai_family = AF_UNSPEC,
+		.ai_socktype = SOCK_STREAM
+	};
+	struct addrinfo *result, *rp;
+	int fd = 0;
+
+	LOG_INFO("CMSIS-DAP: Connecting to %s:%s using TCP backend",
+			cmsis_dap_tcp_host ? cmsis_dap_tcp_host : "localhost",
+			cmsis_dap_tcp_port);
+
+	/* Some of the following code was taken from remote_bitbang.c */
+	/* Obtain address(es) matching host/port */
+	int s = getaddrinfo(cmsis_dap_tcp_host, cmsis_dap_tcp_port, &hints,
+			&result);
+	if (s != 0) {
+		LOG_ERROR("CMSIS-DAP: getaddrinfo: %s\n", gai_strerror(s));
+		free(dap->bdata);
+		return ERROR_FAIL;
+	}
+
+	/* getaddrinfo() returns a list of address structures.
+	 Try each address until we successfully connect(2).
+	 If socket(2) (or connect(2)) fails, we (close the socket
+	 and) try the next address. */
+
+	for (rp = result; rp ; rp = rp->ai_next) {
+		fd = socket(rp->ai_family, rp->ai_socktype, rp->ai_protocol);
+		if (fd == -1)
+			continue;
+
+		if (connect(fd, rp->ai_addr, rp->ai_addrlen) != -1) {
+			LOG_DEBUG("Connected.");
+			break; /* Success */
+		}
+
+		close(fd);
+	}
+
+	freeaddrinfo(result);
+
+	if (!rp) { /* No address succeeded */
+		LOG_ERROR("CMSIS-DAP: unable to connect to device %s:%s",
+			cmsis_dap_tcp_host ? cmsis_dap_tcp_host : "localhost",
+			cmsis_dap_tcp_port);
+		log_socket_error("Failed to connect");
+		free(dap->bdata);
+		dap->bdata = NULL;
+		return ERROR_FAIL;
+	}
+
+	/* Set NODELAY to minimize latency. */
+	int one = 1;
+	/* On Windows optval has to be a const char *. */
+	setsockopt(fd, IPPROTO_TCP, TCP_NODELAY, (const char *)&one, sizeof(one));
+
+	dap->bdata->sockfd = fd;
+
+	int retval = cmsis_dap_tcp_alloc(dap, CMSIS_DAP_PACKET_SIZE);
+	if (retval != ERROR_OK) {
+		cmsis_dap_tcp_close(dap);
+		return retval;
+	}
+	return ERROR_OK;
+}
+
+static void cmsis_dap_tcp_close(struct cmsis_dap *dap)
+{
+	if (close_socket(dap->bdata->sockfd) != 0)
+		log_socket_error("close_socket");
+
+	if (dap->bdata)
+		free(dap->bdata);
+	dap->bdata = NULL;
+	cmsis_dap_tcp_free(dap);
+}
+
+static inline int readall_socket(int handle, void *buffer, unsigned int count)
+{
+	// Return after all count bytes available, or timeout, or error.
+	return recv(handle, buffer, count, MSG_WAITALL);
+}
+
+static inline int peekall_socket(int handle, void *buffer, unsigned int count)
+{
+	/* Data remains unread on the socket until recv() is called later without
+	 * the MSG_PEEK flag. Return after all count bytes available, or timeout,
+	 * or error.
+	 */
+	return recv(handle, buffer, count, MSG_PEEK | MSG_WAITALL);
+}
+
+static int cmsis_dap_tcp_read(struct cmsis_dap *dap, int transfer_timeout_ms,
+							  enum cmsis_dap_blocking blocking)
+{
+	int wait_ms = (blocking == CMSIS_DAP_NON_BLOCKING) ? 0 :
+		transfer_timeout_ms;
+	if (wait_ms) {
+		LOG_DEBUG_IO("CMSIS-DAP: using tcp timeout %d msec", wait_ms);
+
+		// Don't use very short timeouts with TCP/IP as it may not be as fast
+		// to respond as USB. User configurable minimum value.
+		if (wait_ms < cmsis_dap_tcp_min_timeout_ms) {
+			wait_ms = cmsis_dap_tcp_min_timeout_ms;
+			LOG_DEBUG_IO("CMSIS-DAP: extending timeout to %d msec", wait_ms);
+		}
+	}
+	socket_recv_timeout(dap->bdata->sockfd, wait_ms);
+
+	if (blocking == CMSIS_DAP_NON_BLOCKING)
+		socket_nonblock(dap->bdata->sockfd);
+	else
+		socket_block(dap->bdata->sockfd);
+
+	// Peek at the header first to find the length.
+	int retval = peekall_socket(dap->bdata->sockfd, dap->packet_buffer,
+			HEADER_SIZE);
+	LOG_DEBUG_IO("Reading header returned %d", retval);
+	if (retval == 0) {
+		LOG_DEBUG_IO("CMSIS-DAP: tcp timeout reached 1");
+		return ERROR_TIMEOUT_REACHED;
+	} else if (retval == -1) {
+		if (errno == EAGAIN || errno == EWOULDBLOCK) {
+			if (blocking == CMSIS_DAP_NON_BLOCKING)
+				return ERROR_TIMEOUT_REACHED;
+
+			LOG_DEBUG_IO("CMSIS-DAP: tcp timeout reached 2. timeout = %d msec",
+					wait_ms);
+			return ERROR_TIMEOUT_REACHED;
+		}
+
+		LOG_ERROR("CMSIS-DAP: error reading header");
+		log_socket_error("peek_socket");
+		return ERROR_FAIL;
+	} else if (retval != HEADER_SIZE) {
+		LOG_ERROR("CMSIS-DAP: short header read");
+		log_socket_error("peek_socket header short read");
+		return ERROR_FAIL;
+	}
+
+	struct cmsis_dap_tcp_packet_hdr header;
+	header.signature = le_to_h_u32(dap->packet_buffer +
+			HEADER_SIGNATURE_OFFSET);
+	header.length = le_to_h_u16(dap->packet_buffer + HEADER_LENGTH_OFFSET);
+	header.packet_type = dap->packet_buffer[HEADER_PACKET_TYPE_OFFSET];
+	header.reserved = dap->packet_buffer[HEADER_RESERVED_OFFSET];
+
+	if (header.signature != DAP_PKT_HDR_SIGNATURE) {
+		LOG_ERROR("CMSIS-DAP: Unrecognized packet signature 0x%08x",
+				header.signature);
+		return ERROR_FAIL;
+	} else if (header.packet_type != DAP_PKT_TYPE_RESPONSE) {
+		LOG_ERROR("CMSIS-DAP: Unrecognized packet type 0x%02x",
+				header.packet_type);
+		return ERROR_FAIL;
+	} else if (header.length + HEADER_SIZE > dap->packet_buffer_size) {
+		LOG_ERROR("CMSIS-DAP: Packet length %d too large to fit.",
+				header.length);
+		return ERROR_FAIL;
+	}
+
+	// Read the complete packet.
+	int read_len = HEADER_SIZE + header.length;
+	LOG_DEBUG_IO("Reading %d bytes (%d payload)...", read_len, header.length);
+	retval = readall_socket(dap->bdata->sockfd, dap->packet_buffer, read_len);
+
+	if (retval == 0) {
+		LOG_DEBUG_IO("CMSIS-DAP: tcp timeout reached 3");
+		return ERROR_TIMEOUT_REACHED;
+	} else if (retval == -1) {
+		LOG_ERROR("CMSIS-DAP: error reading data");
+		log_socket_error("read_socket");
+		return ERROR_FAIL;
+	} else if (retval != read_len) {
+		LOG_ERROR("CMSIS-DAP: short read. retval = %d. read_len = %d. "
+				"blocking = %s. wait_ms = %d", retval, read_len,
+				(blocking == CMSIS_DAP_NON_BLOCKING) ? "yes" : "no", wait_ms);
+		log_socket_error("read_socket short read");
+		return ERROR_FAIL;
+	}
+	return retval;
+}
+
+static int cmsis_dap_tcp_write(struct cmsis_dap *dap, int txlen,
+		int timeout_ms __attribute__((unused)))
+{
+	const unsigned int len = txlen + HEADER_SIZE;
+	if (len > dap->packet_buffer_size) {
+		LOG_ERROR("CMSIS-DAP: Packet length %d exceeds TCP buffer size!", len);
+		return ERROR_FAIL;
+	}
+
+	/* Set the header values. */
+	h_u32_to_le(dap->packet_buffer + HEADER_SIGNATURE_OFFSET,
+			DAP_PKT_HDR_SIGNATURE);
+	h_u16_to_le(dap->packet_buffer + HEADER_LENGTH_OFFSET, txlen);
+	dap->packet_buffer[HEADER_PACKET_TYPE_OFFSET] = DAP_PKT_TYPE_REQUEST;
+	dap->packet_buffer[HEADER_RESERVED_OFFSET] = 0;
+
+	/* write data to device */
+	LOG_DEBUG_IO("Writing %d bytes (%d payload)", len, txlen);
+	int retval = write_socket(dap->bdata->sockfd, dap->packet_buffer, len);
+	if (retval < 0) {
+		log_socket_error("write_socket");
+		return ERROR_FAIL;
+	} else if (retval != (int)len) {
+		LOG_ERROR("CMSIS-DAP: error writing data");
+		log_socket_error("write_socket short write");
+		return ERROR_FAIL;
+	}
+	return retval;
+}
+
+static int cmsis_dap_tcp_alloc(struct cmsis_dap *dap, unsigned int pkt_sz)
+{
+	// Reserve space for the packet header.
+	unsigned int packet_buffer_size = pkt_sz + HEADER_SIZE;
+	uint8_t *buf = malloc(packet_buffer_size);
+	if (!buf) {
+		LOG_ERROR("CMSIS-DAP: unable to allocate CMSIS-DAP packet buffer");
+		return ERROR_FAIL;
+	}
+
+	dap->packet_buffer = buf;
+	dap->packet_size = pkt_sz;
+	dap->packet_usable_size = pkt_sz;
+	dap->packet_buffer_size = packet_buffer_size;
+
+	dap->command = dap->packet_buffer + HEADER_SIZE;
+	dap->response = dap->packet_buffer + HEADER_SIZE;
+	return ERROR_OK;
+}
+
+static void cmsis_dap_tcp_free(struct cmsis_dap *dap)
+{
+	free(dap->packet_buffer);
+	dap->packet_buffer = NULL;
+}
+
+static void cmsis_dap_tcp_cancel_all(struct cmsis_dap *dap)
+{
+}
+
+COMMAND_HANDLER(cmsis_dap_handle_tcp_port)
+{
+	if (CMD_ARGC != 1)
+		return ERROR_COMMAND_SYNTAX_ERROR;
+
+	if (cmsis_dap_tcp_port != cmsis_dap_tcp_port_default)
+		free(cmsis_dap_tcp_port);
+
+	cmsis_dap_tcp_port = strdup(CMD_ARGV[0]);
+	if (!cmsis_dap_tcp_port) {
+		LOG_ERROR("CMSIS-DAP: out of memory");
+		return ERROR_FAIL;
+	}
+	return ERROR_OK;
+}
+
+COMMAND_HANDLER(cmsis_dap_handle_tcp_host)
+{
+	if (CMD_ARGC != 1)
+		return ERROR_COMMAND_SYNTAX_ERROR;
+
+	free(cmsis_dap_tcp_host);
+	cmsis_dap_tcp_host = strdup(CMD_ARGV[0]);
+	if (!cmsis_dap_tcp_host) {
+		LOG_ERROR("CMSIS-DAP: out of memory");
+		return ERROR_FAIL;
+	}
+	return ERROR_OK;
+}
+
+COMMAND_HANDLER(cmsis_dap_handle_tcp_min_timeout)
+{
+	if (CMD_ARGC != 1)
+		return ERROR_COMMAND_SYNTAX_ERROR;
+
+	COMMAND_PARSE_NUMBER(int, CMD_ARGV[0], cmsis_dap_tcp_min_timeout_ms);
+	LOG_INFO("CMSIS-DAP: using minimum timeout of %d ms for TCP packets.",
+			cmsis_dap_tcp_min_timeout_ms);
+	return ERROR_OK;
+}
+
+const struct command_registration cmsis_dap_tcp_subcommand_handlers[] = {
+	{
+		.name = "host",
+		.handler = &cmsis_dap_handle_tcp_host,
+		.mode = COMMAND_CONFIG,
+		.help = "set the host name to use (for TCP backend only)",
+		.usage = "<host_name>",
+	},
+	{
+		.name = "port",
+		.handler = &cmsis_dap_handle_tcp_port,
+		.mode = COMMAND_CONFIG,
+		.help = "set the port number to use for DAP (for TCP backend only)",
+		.usage = "<port_number>",
+	},
+	{
+		.name = "min_timeout",
+		.handler = &cmsis_dap_handle_tcp_min_timeout,
+		.mode = COMMAND_CONFIG,
+		.help = "set the minimum timeout in milliseconds to wait for response "
+			"packets (for TCP backend only)",
+		.usage = "<milliseconds>",
+	},
+	COMMAND_REGISTRATION_DONE
+};
+
+const struct cmsis_dap_backend cmsis_dap_tcp_backend = {
+	.name = "tcp",
+	.open = cmsis_dap_tcp_open,
+	.close = cmsis_dap_tcp_close,
+	.read = cmsis_dap_tcp_read,
+	.write = cmsis_dap_tcp_write,
+	.packet_buffer_alloc = cmsis_dap_tcp_alloc,
+	.packet_buffer_free = cmsis_dap_tcp_free,
+	.cancel_all = cmsis_dap_tcp_cancel_all,
+};
--- a/tcl/interface/cmsis-dap-tcp.cfg
+++ b/tcl/interface/cmsis-dap-tcp.cfg
@@ -0,0 +1,18 @@
+# SPDX-License-Identifier: GPL-2.0-or-later
+
+#
+# cmsis-dap-tcp - CMSIS-DAP protocol over TCP/IP.
+#
+
+adapter driver cmsis-dap
+cmsis-dap backend tcp
+
+# Specify the hostname or IP address of your programmer.
+# cmsis-dap tcp host 192.168.1.4
+
+# Optionally specify a port number. Default port is 4441.
+# cmsis-dap tcp port 4441
+
+# Optionally set a lower bound on packet timeouts (milliseconds), if using a
+# slow network.
+# cmsis-dap tcp min_timeout 300