Out-of-tree driver - Zephyr (freestanding app)

Question

out-of-tree-driver-test.zip 
 
 Hi, 
 We have a custom board that includes an ST LIS2DE12 sensor. I followed what looks like the normal procedure to create an out-of-tree driver for it by refactoring the Zephyr driver for a similar ST part. I've included the driver in my source tree, and it compiles normally, but won't link with the typical "undefined reference to `__device_dts_ord_xxx'" link error. 
 Note that this is a freestanding application. 
 I've cloned the hello_world application, and added my driver (and an overlay that includes the part). Obviously - it can't run, since the DK board doesn't have the part - but what I'm trying to do is to get it to build without the linker error. I've attached the code to this ticket. 
 What magic do I need to include in my source tree to get my out-of-tree driver to build and link as part of the zephyr tree? 
 Thanks in advance, 
 Cammie

ElectRocnic · Answer

I have found a working solution to this now, thanks to this dicord answer : The problem is indeed, that Zephyr does not seem to clearly document freestanding+out-of-tree applications: You have to include your out-of-tree driver inside your freestanding app root folder like this: ├── drivers
│ ├── CMakeLists.txt
│ ├── Kconfig
│ ├── rtc
│ │ ├── CMakeLists.txt
│ │ ├── Kconfig
│ │ ├── pcf85063a_util.h
│ │ └── pcf85063a.c
│ └── zephyr
│ └── module.yml
├── dts
│ └── bindings
│ └── rtc
│ └── nxp,pcf85063a.yaml
├── include
│ └── app
│ └── drivers
│ └── rtc.h
├── src
└── proj.conf 
 and your driver is actually a so-called "module" which needs the drivers/zephyr/module.yml file with the following content: build:
 cmake: .
 kconfig: Kconfig 
 Next, you need to include this in your app's root CMakeLists.txt before you find the zephyr package (I don't know why, but I got it running this way): 
 list(APPEND ZEPHYR_EXTRA_MODULES
 ${CMAKE_CURRENT_SOURCE_DIR}/drivers
) 
 This is needed instead of the previously (likely, as in my case) used add_subdirectory(drivers) 
 so I removed the latter line in my repo and replaced it with the list command above. 
 Hope, you will find that this solution also works in your case! Kind regards.

Out-of-tree driver - Zephyr (freestanding app)

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