Enhancement: Multi target CMake project support

[imi415]

Currently, MCUXpresso SDK only supports single target in top level CMakeLists.txt, since the components and drivers uses the following method adding source files to the build:

target_sources(${MCUX_SDK_PROJECT_NAME} PRIVATE
    #...something belongs to the component...
)

target_include_directories(${MCUX_SDK_PROJECT_NAME} PUBLIC
   #...some directories needs to be searched...
)

This method requires there could only be one single target (namely ${MCUX_SDK_PROJECT_NAME}), adding another target to the same project (with use cases below) will not work without touching the SDK content or adding them manually.

Typical use cases:

• Linking to somewhere else by changing linker script: SRAM, FlexSPI, SDRAM..etc, you name it.
• Different build configurations, compiler definitions

Possible solution: It would be nice if components are re-organized as static library targets, and built as dependencies of the main executable target... maybe not the best solution, and may requires a lot of effort...

[mcuxsusan]

Thanks for reporting the issue. Will need some time for investigation, the team is quite busy so the reply will be delayed. Appreciate for your patience.

[tq-steina]

A short term solution to this would be integrate #30 as in this case those .cmake files will be included again, with MCUX_SDK_PROJECT_NAME (hopefully) being set to the new project target.

The long-term solution is to use (alias) targets to object libraries. drivers/common/driver_common.cmake might look like this:

#Description: Common Driver; user_visible: True
message("driver_common component is included.")

add_library(driver_common OBJECT
    ${CMAKE_CURRENT_LIST_DIR}/fsl_common.c
    ${CMAKE_CURRENT_LIST_DIR}/fsl_common_arm.c
)

target_include_directories(driver_common PUBLIC
    ${CMAKE_CURRENT_LIST_DIR}/.
)

target_link_libraries(driver_common
    core::driver::reset
    core::devices::CMSIS
)
add_library(core::driver::common ALIAS driver_common)

This is then referenced using

target_link_libraries(${MCUX_SDK_PROJECT_NAME} PRIVATE core::driver::common)

The benefit of aliased targets using :: is that they must be CMake targets. These cannot be fullfilled by some (stray) files. Refer to https://cmake.org/cmake/help/latest/command/target_link_libraries.html

This would look much more like "Modern CMake" where everything is passed using targets and properties and not using variables.

[Badokas]

+1 We need multi-target CMake support for dual-core NXP MCUs.