Implement support for building Mbed as a PlatformIO framework

package.json

@@ -0,0 +1,17 @@
+{
+  "name": "framework-mbed-ce",
+  "version": "6.99.0",
+  "title": "Mbed OS Community Edition",
+  "description": "Mbed CE is a platform operating system designed for the internet of things",
+  "keywords": [
+    "framework",
+    "os",
+    "arm",
+    "hal"
+  ],
+  "homepage": "http://mbed-ce.dev",
+  "repository": {
+    "type": "git",
+    "url": "https://github.com/mbed-ce/mbed-os"
+  }
+}

tools/cmake/mbed_create_distro.cmake

@@ -142,7 +142,7 @@ function(mbed_extract_flags NAME) # ARGN: modules...
 			foreach(SUBMODULE ${SUBMODULES})
 				if(NOT "${SUBMODULE}" MATCHES "::@") # remove CMake internal CMAKE_DIRECTORY_ID_SEP markers
 					# Remove LINK_ONLY genexes from target_link_libraries(... PRIVATE).  We can ignore things wrapped in these
-					# because they will already have been handled by the target_link_libraries earlier on.
+					# because they are for private dependencies.
 					if(NOT "${SUBMODULE}" MATCHES "\\$<LINK_ONLY:.*>")
 						if(NOT ${SUBMODULE} IN_LIST COMPLETED_MODULES)
 							list(APPEND REMAINING_MODULES ${SUBMODULE})

tools/cmake/mbed_generate_configuration.cmake

@@ -11,6 +11,30 @@
 
 set(MBED_NEED_TO_RECONFIGURE FALSE)
 
+# Check that path variables (MBED_APP_JSON_PATH, CUSTOM_TARGETS_JSON_PATH) are valid and set
+# vars (HAS_CUSTOM_TARGETS_JSON, HAS_MBED_APP_JSON) based on whether they exist.
+# Also, convert all relative paths to absolute paths, rooted at CMAKE_SOURCE_DIR.
+# This makes sure that they are interpreted the same way everywhere.
+foreach(json_var_name MBED_APP_JSON CUSTOM_TARGETS_JSON)
+
+    if("${${json_var_name}_PATH}" STREQUAL "")
+        set(HAS_${json_var_name} FALSE)
+    else()
+        get_filename_component(${json_var_name}_PATH "${${json_var_name}_PATH}" ABSOLUTE BASE_DIR ${CMAKE_SOURCE_DIR})
+        if(NOT EXISTS ${${json_var_name}_PATH} OR IS_DIRECTORY ${${json_var_name}_PATH})
+            message(FATAL_ERROR "${json_var_name}_PATH value of ${${json_var_name}_PATH} is not a valid file!")
+        endif()
+        set(HAS_${json_var_name} TRUE)
+    endif()
+endforeach()
+
+if("${CUSTOM_TARGETS_JSON_PATH}" STREQUAL "")
+    set(HAS_CUSTOM_TARGETS_JSON FALSE)
+else()
+    set(HAS_CUSTOM_TARGETS_JSON TRUE)
+    get_filename_component(CUSTOM_TARGETS_JSON_PATH "${CUSTOM_TARGETS_JSON_PATH}" ABSOLUTE BASE_DIR ${CMAKE_SOURCE_DIR})
+endif()
+
 # First, verify that MBED_TARGET has not changed
 if(DEFINED MBED_INTERNAL_LAST_MBED_TARGET)
     if(NOT "${MBED_INTERNAL_LAST_MBED_TARGET}" STREQUAL "${MBED_TARGET}")
@@ -42,9 +66,19 @@ endif()
 if(NOT MBED_NEED_TO_RECONFIGURE)
     file(TIMESTAMP ${CMAKE_CURRENT_BINARY_DIR}/mbed_config.cmake MBED_CONFIG_CMAKE_TIMESTAMP "%s" UTC)
 
+    set(MBED_APP_JSON_FOUND FALSE)
+    set(CUSTOM_TARGETS_JSON_FOUND FALSE)
+
     foreach(CONFIG_JSON ${MBED_CONFIG_JSON_SOURCE_FILES})
         get_filename_component(CONFIG_JSON_ABSPATH ${CONFIG_JSON} ABSOLUTE)
 
+        if(CONFIG_JSON_ABSPATH STREQUAL MBED_APP_JSON_PATH)
+            set(MBED_APP_JSON_FOUND TRUE)
+        endif()
+        if(CONFIG_JSON_ABSPATH STREQUAL CUSTOM_TARGETS_JSON_PATH)
+            set(CUSTOM_TARGETS_JSON_FOUND TRUE)
+        endif()
+
         if(NOT EXISTS ${CONFIG_JSON_ABSPATH})
             message(STATUS "Mbed: ${CONFIG_JSON} deleted or renamed, regenerating configs...")
             set(MBED_NEED_TO_RECONFIGURE TRUE)
@@ -60,20 +94,28 @@ if(NOT MBED_NEED_TO_RECONFIGURE)
     endforeach()
 endif()
 
-# Convert all relative paths to absolute paths, rooted at CMAKE_SOURCE_DIR.
-# This makes sure that they are interpreted the same way everywhere.
-get_filename_component(MBED_APP_JSON_PATH "${MBED_APP_JSON_PATH}" ABSOLUTE BASE_DIR ${CMAKE_SOURCE_DIR})
-get_filename_component(CUSTOM_TARGETS_JSON_PATH "${CUSTOM_TARGETS_JSON_PATH}" ABSOLUTE BASE_DIR ${CMAKE_SOURCE_DIR})
+if(NOT MBED_NEED_TO_RECONFIGURE)
+    # Corner case: if we previously had not set an mbed_app.json and now we do, we need to detect that
+    # and reconfigure.
+    if(HAS_MBED_APP_JSON AND NOT MBED_APP_JSON_FOUND)
+        message(STATUS "Mbed: mbed_app.json added/moved, regenerating configs...")
+        set(MBED_NEED_TO_RECONFIGURE TRUE)
+    endif()
+    if(HAS_CUSTOM_TARGETS_JSON AND NOT CUSTOM_TARGETS_JSON_FOUND)
+        message(STATUS "Mbed: custom_targets.json added/moved, regenerating configs...")
+        set(MBED_NEED_TO_RECONFIGURE TRUE)
+    endif()
+endif()
 
 if(MBED_NEED_TO_RECONFIGURE)
     # Generate mbed_config.cmake for this target
-    if(EXISTS "${MBED_APP_JSON_PATH}" AND (NOT IS_DIRECTORY "${MBED_APP_JSON_PATH}"))
+    if(HAS_MBED_APP_JSON)
         set(APP_CONFIG_ARGUMENT --app-config "${MBED_APP_JSON_PATH}")
     else()
         set(APP_CONFIG_ARGUMENT "")
     endif()
 
-    if(EXISTS "${CUSTOM_TARGETS_JSON_PATH}" AND (NOT IS_DIRECTORY "${CUSTOM_TARGETS_JSON_PATH}"))
+    if(HAS_CUSTOM_TARGETS_JSON)
         set(CUSTOM_TARGET_ARGUMENT --custom-targets-json "${CUSTOM_TARGETS_JSON_PATH}")
     else()
         set(CUSTOM_TARGET_ARGUMENT "")

tools/pyproject.toml

@@ -72,6 +72,13 @@ unit-tests = [
     "lxml"
 ]
 
+# Install this optional dependency group to get IDE completion for packages used by the mbed_platformio package.
+# Note that this package is actually run in platformio's venv, not the Mbed venv, so there is no other need to install these.
+platformio = [
+    "SCons",
+    "platformio"
+]
+
 [tool.hatch.build.targets.wheel]
 packages = [
     "python/mbed_host_tests",

tools/python/mbed_platformio/CMakeLists.txt

@@ -0,0 +1,22 @@
+#
+# This file is used as the CMakeLists.txt when building a PlatformIO project.
+#
+
+cmake_minimum_required(VERSION 3.19)
+cmake_policy(VERSION 3.19...3.22)
+
+set(MBED_APP_JSON_PATH ${PLATFORMIO_PROJECT_PATH}/mbed_app.json5)
+
+include(${PLATFORMIO_MBED_OS_PATH}/tools/cmake/mbed_toolchain_setup.cmake)
+project(PlatformIOMbedProject
+        LANGUAGES C CXX ASM)
+include(mbed_project_setup)
+
+add_subdirectory(${PLATFORMIO_MBED_OS_PATH} mbed-os)
+
+# Dummy executable. Not built, but needed to get the compile and linker flags via the CMake file API
+add_executable(PIODummyExecutable
+    dummy_source_file.c
+    dummy_source_file.cpp
+    dummy_source_file.S)
+target_link_libraries(PIODummyExecutable mbed-os)

tools/python/mbed_platformio/__init__.py

@@ -0,0 +1,4 @@
+"""
+Copyright (c) 2025 Jamie Smith
+SPDX-License-Identifier: Apache-2.0
+"""