system/microros: Add UDP and serial custom transport backends.

Micro XRCE-DDS expects the application to supply open/close/write/read
callbacks for the wire transport. Add a single dispatcher that
registers the selected backend via rmw_uros_set_custom_transport(),
plus two backends:

transport/microros_transport_udp.c
  BSD-socket UDP backend. Opens an AF_INET/SOCK_DGRAM socket,
  resolves CONFIG_MICROROS_AGENT_IP/PORT, connect()s it, and uses
  send/recv. The socket fd is stashed in uxrCustomTransport->args
  so no module-level state is needed.

transport/microros_transport_serial.c
  termios serial backend. Opens CONFIG_MICROROS_SERIAL_DEVICE with
  O_RDWR|O_NOCTTY|O_CLOEXEC, switches to raw 8N1 at
  CONFIG_MICROROS_SERIAL_BAUD, and uses poll/read/write. Fd is
  again stashed in uxrCustomTransport->args.

Both backends are mutually exclusive at compile time via Kconfig;
the dispatcher selects which set of callbacks to register. Wired
into both the legacy Make build (CSRCS in system/microros/Makefile)
and the CMake build (separate microros_transport static library
with the transport directory only exposed to its INTERFACE).

Signed-off-by: Arjav Patel <arjav1528@gmail.com>

include/system/microros_transport.h

@@ -0,0 +1,50 @@
+/****************************************************************************
+ * apps/include/system/microros_transport.h
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ *
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.  The
+ * ASF licenses this file to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance with the
+ * License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.  See the
+ * License for the specific language governing permissions and limitations
+ * under the License.
+ *
+ ****************************************************************************/
+
+#ifndef __APPS_INCLUDE_SYSTEM_MICROROS_TRANSPORT_H
+#define __APPS_INCLUDE_SYSTEM_MICROROS_TRANSPORT_H
+
+#ifdef __cplusplus
+extern "C"
+{
+#endif
+
+/****************************************************************************
+ * Public Function Prototypes
+ ****************************************************************************/
+
+/* microros_transport_init
+ *
+ * Register the NuttX-native transport (UDP or Serial, selected by Kconfig)
+ * with the rmw_microxrcedds layer.  Must be called once before
+ * rclc_support_init().
+ *
+ * Returns 0 on success, negated errno on failure.
+ */
+
+int microros_transport_init(void);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* __APPS_INCLUDE_SYSTEM_MICROROS_TRANSPORT_H */

system/microros/CMakeLists.txt

@@ -44,4 +44,24 @@ if(CONFIG_SYSTEM_MICROROS)
     microros PROPERTIES IMPORTED_LOCATION ${MICROROS_DIR}/libmicroros.a
                         INTERFACE_INCLUDE_DIRECTORIES ${MICROROS_DIR}/include)
   add_dependencies(microros microros_build)
+
+  # Transport glue compiled into the apps tree
+  set(MICROROS_TRANSPORT_SRCS ${MICROROS_DIR}/transport/microros_transport.c)
+
+  if(CONFIG_MICROROS_TRANSPORT_UDP)
+    list(APPEND MICROROS_TRANSPORT_SRCS
+         ${MICROROS_DIR}/transport/microros_transport_udp.c)
+  endif()
+
+  if(CONFIG_MICROROS_TRANSPORT_SERIAL)
+    list(APPEND MICROROS_TRANSPORT_SRCS
+         ${MICROROS_DIR}/transport/microros_transport_serial.c)
+  endif()
+
+  nuttx_add_library(microros_transport STATIC)
+  target_sources(microros_transport PRIVATE ${MICROROS_TRANSPORT_SRCS})
+  target_include_directories(microros_transport
+                             PRIVATE ${MICROROS_DIR}/transport)
+  target_include_directories(microros_transport PUBLIC ${MICROROS_DIR}/include)
+  add_dependencies(microros_transport microros_build)
 endif()

system/microros/Makefile

@@ -25,7 +25,7 @@ include $(APPDIR)/Make.defs
 MICROROS_DIR     := $(APPDIR)/system/microros
 MICROROS_LIB_DIR := $(MICROROS_DIR)/micro_ros_lib
 MICROROS_DISTRO  := $(patsubst "%",%,$(CONFIG_MICROROS_DISTRO))
-MICROROS_AR      := $(CROSSDEV)ar
+MICROROS_AR      := $(firstword $(AR))
 
 MAX_NODES   := $(CONFIG_MICROROS_MAX_NODES)
 MAX_PUB     := $(CONFIG_MICROROS_MAX_PUBLISHERS)
@@ -44,6 +44,18 @@ ESCAPED_CXXFLAGS := $(subst /,\/,$(subst ",,$(CXXFLAGS)))
 
 MENUDESC = "micro-ROS Library"
 
+# Transport sources compiled into the user-side app library
+
+CSRCS += transport/microros_transport.c
+
+ifeq ($(CONFIG_MICROROS_TRANSPORT_UDP),y)
+CSRCS += transport/microros_transport_udp.c
+endif
+
+ifeq ($(CONFIG_MICROROS_TRANSPORT_SERIAL),y)
+CSRCS += transport/microros_transport_serial.c
+endif
+
 # Architecture for CMake toolchain
 ifeq ($(CONFIG_ARCH_ARM),y)
 MICROROS_ARCH := arm

system/microros/transport/microros_transport.c

@@ -0,0 +1,62 @@
+/****************************************************************************
+ * apps/system/microros/transport/microros_transport.c
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ *
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.  The
+ * ASF licenses this file to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance with the
+ * License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.  See the
+ * License for the specific language governing permissions and limitations
+ * under the License.
+ *
+ ****************************************************************************/
+
+/****************************************************************************
+ * Included Files
+ ****************************************************************************/
+
+#include <nuttx/config.h>
+
+#include <errno.h>
+
+#include <rmw_microros/rmw_microros.h>
+
+#include <system/microros_transport.h>
+
+#include "microros_transport.h"
+
+/****************************************************************************
+ * Public Functions
+ ****************************************************************************/
+
+int microros_transport_init(void)
+{
+#if defined(CONFIG_MICROROS_TRANSPORT_UDP)
+  rmw_uros_set_custom_transport(false,
+                                NULL,
+                                microros_udp_open,
+                                microros_udp_close,
+                                microros_udp_write,
+                                microros_udp_read);
+  return 0;
+#elif defined(CONFIG_MICROROS_TRANSPORT_SERIAL)
+  rmw_uros_set_custom_transport(true,
+                                NULL,
+                                microros_serial_open,
+                                microros_serial_close,
+                                microros_serial_write,
+                                microros_serial_read);
+  return 0;
+#else
+  return -ENOSYS;
+#endif
+}

system/microros/transport/microros_transport.h

@@ -0,0 +1,67 @@
+/****************************************************************************
+ * apps/system/microros/transport/microros_transport.h
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ *
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.  The
+ * ASF licenses this file to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance with the
+ * License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.  See the
+ * License for the specific language governing permissions and limitations
+ * under the License.
+ *
+ ****************************************************************************/
+
+#ifndef __APPS_SYSTEM_MICROROS_TRANSPORT_MICROROS_TRANSPORT_H
+#define __APPS_SYSTEM_MICROROS_TRANSPORT_MICROROS_TRANSPORT_H
+
+/****************************************************************************
+ * Included Files
+ ****************************************************************************/
+
+#include <stdbool.h>
+#include <stddef.h>
+#include <stdint.h>
+
+#include <uxr/client/profile/transport/custom/custom_transport.h>
+
+#ifdef __cplusplus
+extern "C"
+{
+#endif
+
+/****************************************************************************
+ * Public Function Prototypes
+ ****************************************************************************/
+
+/* Backend callbacks.  Exposed for testing only. */
+
+bool   microros_udp_open(struct uxrCustomTransport *transport);
+bool   microros_udp_close(struct uxrCustomTransport *transport);
+size_t microros_udp_write(struct uxrCustomTransport *transport,
+                          const uint8_t *buf, size_t len, uint8_t *err);
+size_t microros_udp_read(struct uxrCustomTransport *transport,
+                         uint8_t *buf, size_t len,
+                         int timeout_ms, uint8_t *err);
+
+bool   microros_serial_open(struct uxrCustomTransport *transport);
+bool   microros_serial_close(struct uxrCustomTransport *transport);
+size_t microros_serial_write(struct uxrCustomTransport *transport,
+                             const uint8_t *buf, size_t len, uint8_t *err);
+size_t microros_serial_read(struct uxrCustomTransport *transport,
+                            uint8_t *buf, size_t len,
+                            int timeout_ms, uint8_t *err);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* __APPS_SYSTEM_MICROROS_TRANSPORT_MICROROS_TRANSPORT_H */

system/microros/transport/microros_transport_serial.c

@@ -0,0 +1,216 @@
+/****************************************************************************
+ * apps/system/microros/transport/microros_transport_serial.c
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ *
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.  The
+ * ASF licenses this file to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance with the
+ * License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.  See the
+ * License for the specific language governing permissions and limitations
+ * under the License.
+ *
+ ****************************************************************************/
+
+/****************************************************************************
+ * Included Files
+ ****************************************************************************/
+
+#include <nuttx/config.h>
+
+#include <fcntl.h>
+#include <poll.h>
+#include <stdint.h>
+#include <termios.h>
+#include <unistd.h>
+
+#include "microros_transport.h"
+
+/****************************************************************************
+ * Private Helpers
+ ****************************************************************************/
+
+static inline int serial_fd(struct uxrCustomTransport *transport)
+{
+  return (int)(intptr_t)transport->args - 1;
+}
+
+static inline void serial_set_fd(struct uxrCustomTransport *transport,
+                                 int fd)
+{
+  transport->args = (void *)(intptr_t)(fd + 1);
+}
+
+static int set_baud(struct termios *tio, int baud)
+{
+  speed_t s;
+
+  switch (baud)
+    {
+      case 9600:
+        s = B9600;
+        break;
+
+      case 19200:
+        s = B19200;
+        break;
+
+      case 38400:
+        s = B38400;
+        break;
+
+      case 57600:
+        s = B57600;
+        break;
+
+      case 115200:
+        s = B115200;
+        break;
+
+      case 230400:
+        s = B230400;
+        break;
+
+      case 460800:
+        s = B460800;
+        break;
+
+      case 921600:
+        s = B921600;
+        break;
+
+      default:
+        return -1;
+    }
+
+  cfsetispeed(tio, s);
+  cfsetospeed(tio, s);
+  return 0;
+}
+
+/****************************************************************************
+ * Public Functions
+ ****************************************************************************/
+
+bool microros_serial_open(struct uxrCustomTransport *transport)
+{
+  struct termios tio;
+  int fd;
+
+  fd = open(CONFIG_MICROROS_SERIAL_DEVICE, O_RDWR | O_NOCTTY | O_CLOEXEC);
+  if (fd < 0)
+    {
+      return false;
+    }
+
+  if (tcgetattr(fd, &tio) < 0)
+    {
+      close(fd);
+      return false;
+    }
+
+  cfmakeraw(&tio);
+  tio.c_cflag |= (CLOCAL | CREAD);
+  tio.c_cflag &= ~CRTSCTS;
+  tio.c_cc[VMIN]  = 0;
+  tio.c_cc[VTIME] = 0;
+
+  if (set_baud(&tio, CONFIG_MICROROS_SERIAL_BAUD) < 0)
+    {
+      close(fd);
+      return false;
+    }
+
+  if (tcsetattr(fd, TCSANOW, &tio) < 0)
+    {
+      close(fd);
+      return false;
+    }
+
+  tcflush(fd, TCIOFLUSH);
+  serial_set_fd(transport, fd);
+  return true;
+}
+
+bool microros_serial_close(struct uxrCustomTransport *transport)
+{
+  int fd = serial_fd(transport);
+
+  if (fd >= 0)
+    {
+      close(fd);
+      serial_set_fd(transport, -1);
+    }
+
+  return true;
+}
+
+size_t microros_serial_write(struct uxrCustomTransport *transport,
+                             const uint8_t *buf, size_t len, uint8_t *err)
+{
+  int fd = serial_fd(transport);
+  ssize_t n;
+
+  if (fd < 0)
+    {
+      *err = 1;
+      return 0;
+    }
+
+  n = write(fd, buf, len);
+  if (n < 0)
+    {
+      *err = 1;
+      return 0;
+    }
+
+  return n;
+}
+
+size_t microros_serial_read(struct uxrCustomTransport *transport,
+                            uint8_t *buf, size_t len,
+                            int timeout_ms, uint8_t *err)
+{
+  int fd = serial_fd(transport);
+  struct pollfd pfd;
+  ssize_t n;
+  int r;
+
+  if (fd < 0)
+    {
+      *err = 1;
+      return 0;
+    }
+
+  pfd.fd     = fd;
+  pfd.events = POLLIN;
+
+  r = poll(&pfd, 1, timeout_ms);
+  if (r < 0)
+    {
+      *err = 1;
+      return 0;
+    }
+
+  if (r == 0)
+    {
+      return 0;
+    }
+
+  n = read(fd, buf, len);
+  if (n < 0)
+    {
+      *err = 1;
+      return 0;
+    }
+
+  return n;
+}

system/microros/transport/microros_transport_udp.c

@@ -0,0 +1,162 @@
+/****************************************************************************
+ * apps/system/microros/transport/microros_transport_udp.c
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ *
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.  The
+ * ASF licenses this file to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance with the
+ * License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.  See the
+ * License for the specific language governing permissions and limitations
+ * under the License.
+ *
+ ****************************************************************************/
+
+/****************************************************************************
+ * Included Files
+ ****************************************************************************/
+
+#include <nuttx/config.h>
+
+#include <arpa/inet.h>
+#include <netinet/in.h>
+#include <poll.h>
+#include <stdint.h>
+#include <string.h>
+#include <sys/socket.h>
+#include <sys/types.h>
+#include <unistd.h>
+
+#include "microros_transport.h"
+
+/****************************************************************************
+ * Private Helpers
+ ****************************************************************************/
+
+static inline int udp_fd(struct uxrCustomTransport *transport)
+{
+  return (int)(intptr_t)transport->args - 1;
+}
+
+static inline void udp_set_fd(struct uxrCustomTransport *transport, int fd)
+{
+  transport->args = (void *)(intptr_t)(fd + 1);
+}
+
+/****************************************************************************
+ * Public Functions
+ ****************************************************************************/
+
+bool microros_udp_open(struct uxrCustomTransport *transport)
+{
+  struct sockaddr_in addr;
+  int fd;
+
+  fd = socket(AF_INET, SOCK_DGRAM | SOCK_CLOEXEC, 0);
+  if (fd < 0)
+    {
+      return false;
+    }
+
+  memset(&addr, 0, sizeof(addr));
+  addr.sin_family = AF_INET;
+  addr.sin_port   = htons(CONFIG_MICROROS_AGENT_PORT);
+
+  if (inet_pton(AF_INET, CONFIG_MICROROS_AGENT_IP, &addr.sin_addr) != 1)
+    {
+      close(fd);
+      return false;
+    }
+
+  if (connect(fd, (struct sockaddr *)&addr, sizeof(addr)) < 0)
+    {
+      close(fd);
+      return false;
+    }
+
+  udp_set_fd(transport, fd);
+  return true;
+}
+
+bool microros_udp_close(struct uxrCustomTransport *transport)
+{
+  int fd = udp_fd(transport);
+
+  if (fd >= 0)
+    {
+      close(fd);
+      udp_set_fd(transport, -1);
+    }
+
+  return true;
+}
+
+size_t microros_udp_write(struct uxrCustomTransport *transport,
+                          const uint8_t *buf, size_t len, uint8_t *err)
+{
+  int fd = udp_fd(transport);
+  ssize_t n;
+
+  if (fd < 0)
+    {
+      *err = 1;
+      return 0;
+    }
+
+  n = send(fd, buf, len, 0);
+  if (n < 0)
+    {
+      *err = 1;
+      return 0;
+    }
+
+  return n;
+}
+
+size_t microros_udp_read(struct uxrCustomTransport *transport,
+                         uint8_t *buf, size_t len,
+                         int timeout_ms, uint8_t *err)
+{
+  int fd = udp_fd(transport);
+  struct pollfd pfd;
+  ssize_t n;
+  int r;
+
+  if (fd < 0)
+    {
+      *err = 1;
+      return 0;
+    }
+
+  pfd.fd     = fd;
+  pfd.events = POLLIN;
+
+  r = poll(&pfd, 1, timeout_ms);
+  if (r < 0)
+    {
+      *err = 1;
+      return 0;
+    }
+
+  if (r == 0)
+    {
+      return 0;
+    }
+
+  n = recv(fd, buf, len, 0);
+  if (n < 0)
+    {
+      *err = 1;
+      return 0;
+    }
+
+  return n;
+}