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

[Cammie]

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]

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.

[Mirco]

You are my savior!