Added LwIP support for stm32-cmake

README.md

@@ -39,6 +39,11 @@ It uses cmake and GCC, along with newlib (libc), STM32Cube. Supports F0 F1 F2 F3
    You can opt to use the FreeRTOS CMSIS implementation provided by the Cube repository by supplying
    `USE_CMSIS_RTOS=ON` or `USE_CMSIS_RTOS_V2` to CMake.
 
+The `lwip` support does not have a dedicated example because most STM devices have different PHYs
+and/or there is machine and linker script specific code which makes it difficult to create a
+generic example. You can find an UDP echo server application for the H743ZI board
+[here](https://github.com/robamu-org/stm32-cmake-projects).
+
 # Usage
 
 First of all you need to configure toolchain and library paths using CMake variables. There are
@@ -287,3 +292,30 @@ Other FreeRTOS libraries, with `FREERTOS_NAMESPACE` being set as specified in th
 * `${FREERTOS_NAMESPACE}::StreamBuffer` - stream buffer (`stream_buffer.c`)
 * `${FREERTOS_NAMESPACE}::Timers` - timers (`timers.c`)
 * `${FREERTOS_NAMESPACE}::Heap::<N>` - heap implementation (`heap_<N>.c`), `<N>`: [1-5]
+
+## <a id="lwip"></a> LwIP
+
+[cmake/FindLwIP](cmake/FindLwIP.cmake) - finds LwIP sources in STM32Cube repository and format them
+as `IMPORTED` targets. This requires a `lwipopts.h` in the application include path to work.
+If the Netconn or Socket API is used, the CMSIS support needs to be linked like specified in
+the [FreeRTOS section](#freertos).
+
+Available LwIP libraries:
+
+* `LwIP::IPv4` - IPv4 support
+* `LwIP::IPv6` - IPv6 support
+* `LwIP::SYS` - System support (`sys_arch.c`)
+* `LwIP::API` - Support for Netconn and Socket API. Will also link `LwIP::SYS` automatically
+* `LwIP::NETIF` - Netif sources support
+
+Typical usage when using Raw API to implement a simple UDP echoserver
+
+```cmake
+find_package(LwIP REQUIRED)
+target_link_libraries(${TARGET_NAME} PRIVATE
+    ...
+    LwIP
+    LwIP::IPv4
+    LwIP::NETIF
+)
+```

cmake/FindLwIP.cmake

@@ -0,0 +1,87 @@
+# If NO_SYS is set to 0 and the Netconn or Socket API is used, the user should link against
+# the CMSIS RTOS or RTOS_V2 support because the sys_arch.c LwIP OS port layer makes use of
+# CMSIS calls.
+find_path(LwIP_ROOT
+    NAMES CMakeLists.txt
+    PATHS "${STM32_CUBE_${FAMILY}_PATH}/Middlewares/Third_Party/LwIP"
+    NO_DEFAULT_PATH
+)
+
+if(LwIP_ROOT MATCHES "LwIP_ROOT-NOTFOUND")
+    message(WARNING "LwIP root foolder not found. LwIP might not be supported")
+endif()
+
+set(LWIP_DIR ${LwIP_ROOT})
+
+find_path(LwIP_SOURCE_PATH
+    NAMES Filelists.cmake
+    PATHS "${STM32_CUBE_${FAMILY}_PATH}/Middlewares/Third_Party/LwIP/src"
+    NO_DEFAULT_PATH
+)
+
+if(LwIP_SOURCE_PATH MATCHES "LwIP_SOURCE_PATH-NOTFOUND")
+    message(WARNING "LwIP filelist CMake file not found. Build might fail")
+endif()
+
+if(IS_DIRECTORY "${LwIP_SOURCE_PATH}/include")
+    set(LwIP_INCLUDE_DIR "${LwIP_SOURCE_PATH}/include")
+else()
+    message(WARNING "LwIP include directory not found. Build might fail")
+endif()
+
+if(IS_DIRECTORY "${LwIP_ROOT}/system")
+    set(LwIP_SYS_INCLUDE_DIR "${LwIP_ROOT}/system")
+    set(LwIP_SYS_SOURCES "${LwIP_ROOT}/system/OS/sys_arch.c")
+else()
+    message(WARNING "LwIP system include directory not found. Build might fail")
+endif()
+
+# Use Filelists.cmake to get list of sources to compile
+include("${LwIP_SOURCE_PATH}/Filelists.cmake")
+
+if(NOT (TARGET LwIP))
+    add_library(LwIP INTERFACE IMPORTED)
+    target_sources(LwIP INTERFACE ${lwipcore_SRCS})
+    target_include_directories(LwIP INTERFACE
+        ${LwIP_INCLUDE_DIR} ${LwIP_SYS_INCLUDE_DIR}
+    )
+endif()
+
+# Compile the system components which use CMSIS RTOS. This is necessary for the NETIF and Socket API
+# This target also requires that the application was linked against the CMSIS RTOS support
+if(NOT (TARGET LwIP::SYS))
+    add_library(LwIP::SYS INTERFACE IMPORTED)
+    target_sources(LwIP::SYS INTERFACE ${LwIP_SYS_SOURCES})
+    target_link_libraries(LwIP::SYS INTERFACE LwIP)
+endif()
+
+if(NOT (TARGET LwIP::IPv4))
+    add_library(LwIP::IPv4 INTERFACE IMPORTED)
+    target_sources(LwIP::IPv4 INTERFACE ${lwipcore4_SRCS})
+    target_link_libraries(LwIP::IPv4 INTERFACE LwIP)
+endif()
+
+if(NOT (TARGET LwIP::IPv6))
+    add_library(LwIP::IPv6 INTERFACE IMPORTED)
+    target_sources(LwIP::IPv6 INTERFACE ${lwipcore6_SRCS})
+    target_link_libraries(LwIP::IPv6 INTERFACE LwIP)
+endif()
+
+if(NOT (TARGET LwIP::API))
+    add_library(LwIP::API INTERFACE IMPORTED)
+    target_sources(LwIP::API INTERFACE ${lwipapi_SRCS})
+    target_link_libraries(LwIP::API INTERFACE LwIP::SYS)
+endif()
+
+if(NOT (TARGET LwIP::NETIF))
+    add_library(LwIP::NETIF INTERFACE IMPORTED)
+    target_sources(LwIP::NETIF INTERFACE ${lwipnetif_SRCS})
+    target_link_libraries(LwIP::NETIF INTERFACE LwIP)
+endif()
+
+include(FindPackageHandleStandardArgs)
+find_package_handle_standard_args(LwIP
+    REQUIRED_VARS LwIP_ROOT LwIP_INCLUDE_DIR LwIP_SYS_INCLUDE_DIR
+    FOUND_VAR LwIP_FOUND
+    HANDLE_COMPONENTS
+)