Difference between `zephyr_library_sources()` and `target_sources()` in CMakeLists.txt

[Jayant Tang]

Hello everyone,

I'm developing a demo to create my own driver using DeviceTree. And I defined the device in the driver source files.

I called the driver API in the `main.c`. But when I added the driver files to my project, there is an error when linking.

The linker says: `undefined reference to `__device_dts_ord_14'`.

It means that the linker can't find the device structure defined by the driver source.

But when I change my CMakeLists.txt, from `zephyr_library_sources()` to `target_sources(app )`，it was successfully built.

See:

 

# The config that causes link error
# zephyr_include_directories(.)
# zephyr_library()
# zephyr_library_sources_ifdef(CONFIG_JAYANT_VOLTAGE_SENSOR  voltage-sensor.c)
# zephyr_library_sources_ifdef(CONFIG_JAYANT_BLINK_LED       blink-led.c)


# The config that build successfully
target_include_directories(app PRIVATE .)
target_sources_ifdef(CONFIG_JAYANT_VOLTAGE_SENSOR app PRIVATE  voltage-sensor.c)
target_sources_ifdef(CONFIG_JAYANT_BLINK_LED      app PRIVATE  blink-led.c)

I want to know the difference between the 2 ways to add source files.

I learned the 1st way from the driver code in `zephyr/driver/`.  So I think it's a right way to add driver code to a project.

I have no ideas about why my own driver code can only be added as application.

[Einarh]

Hello

From what I understand these zephyr_* commands are just wrappers for the corresponding CMake commands, as discussed here:

https://github.com/zephyrproject-rtos/zephyr/issues/8439

zephyr_library_sources() = target_sources( PRIVATE )

I believe what is happening in your case could be because of zephyr_library() adding a library named after the folder it's called in, which for example in the case of zephyr/drivers/spi/CmakeLists.txt will make the library "spi". Maybe this could explain your linker error?

Best regards,

Einar

[Jayant Tang]

Yes, you're right. If someone wants to add code as module in zephyr, there must be a module name to be set.

I just solved this problem by referring to https://docs.zephyrproject.org/latest/develop/modules.html#integrate-modules-in-zephyr-build-system

Below are my steps:

1. add a zephyr/module.yml file to my driver folder. the zephyr subfolder is required.

2. Modify the project's CMakeLists.txt

This command will add drivers folder to Zephyr as extra module.

And the command must be invoked before `find_package(Zephyr)`

3. Then I can write the drivers/CMakeLists.txt in the way of module:

 

[Aloysious Benoy]

The zephyr doc page you mentioned says :

So do I have to modify the project cmake file as mentioned in step 2?

[Jayant Tang]

I think it's needed. My module code is placed outside of the SDK, so it is a extra module.

I have to modify the CMakeLists.txt to let Zephyr know it's path.