DT_NODE_EXISTS() is true but DEVICE_DT_GET() expands to nothing

[5frank]

Describe the bug

If a device driver depends on FOO and FOO=n, then DT_NODE_EXISTS(foo_dev) is true but DEVICE_DT_GET(foo_dev) expands to nothing
(i.e compiler error undefined reference to __device_dts_ord_NN)

To Reproduce
See attached app. It uses the ws2812-gpio driver for ESP32 but the driver depends on a nordic SOC.

reproduce_app.zip

Environment (please complete the following information):

• OS: Linux/Debian
• CMake version: 3.22.3
• toolchain: zephyr 0.16.0
• zephyr latest (SHA 20faa0e)

[5frank]

Perhaps I should add that there is a Kconfig warning on 'unsatisfied dependencies' but I still think it qualifies as bug as DT_NODE_EXISTS() is quite useful in code that runs on different boards.

[pdgendt]

I think this is intended behavior, there's no limitation for DT_NODE_EXISTS to "know" about dependencies, it simply verifies the generated device tree. It's up to the user to set the status to "disabled" in this case.

The linker error undefined reference to __device_dts_ord_NN has been the subject of many discussions and could be improved upon.

[pdgendt]

It is even stated in the troubleshooting documentation that Kconfig option need to be enabled.

[mbolivar]

This is not a bug. In addition to the docs that @pdgendt pointed you to, you can also watch my talk https://www.youtube.com/watch?v=w8GgP3h0M8M for an explanation of why you are seeing this