Device Tree Magic Macros

[Jerry Easley]

I am trying to understand what is compiled when "Device Tree Magic Macros" are used to extract information from the device tree.  For example, I would like to see what is compiled when the following statements are encountered by the preprocessor:

#define DEVICE_NODE DT_COMPAT_GET_ANY_STATUS_OKAY(ti_fdc2x1x)

int main(void)

{

struct sensor_value ch_buf[] = {

DT_FOREACH_CHILD(DEVICE_NODE, CH_BUF_INIT)

};

My purpose here is to understand how this works; I have found the documentation to be incomprehensible.

My intuition is to run the compiler with -E flag set but I can't figure out how to do that under vscode/nrf_sdk.

Any suggestions?

Regards,

Jerry

[Hieu]

Hi Jerry,

My intuition is to run the compiler with -E flag set but I can't figure out how to do that under vscode/nrf_sdk.

There is a relevant discussion on this on GitHub here: https://github.com/zephyrproject-rtos/zephyr/issues/8329.

There is also a method to keep preprocessed source files explained here: Troubleshooting devicetree — Zephyr Project documentation (nRF Connect SDK) (nordicsemi.com).

Trying to expand the macro like Patrick said is an option. I could not get it to work like they said, but hover the mouse over the macro gives me its expanded form. I searched further and can replace it inline using the IDE with the method described here: https://github.com/microsoft/vscode-cpptools/issues/4183#issuecomment-865443907.

However, my understanding is that you want to understand how the macros are expanded. If so, you will want to look into these resources:

• Devicetree access from C/C++ — Zephyr Project documentation (nRF Connect SDK) (nordicsemi.com)
  You might want to get a general idea of the terms used from this page.
  It's also a good idea to understand the the relevant concepts from the parent page here: Devicetree — Zephyr Project documentation (nRF Connect SDK) (nordicsemi.com)
  
  
• The macros are defined in https://github.com/nrfconnect/sdk-zephyr/blob/v3.3.99-ncs1/include/zephyr/devicetree.h
  
  
• The header file where all the Devicetree nodes are compiled and generated is <build directory>/zephyr/include/generated/devicetree_generated.h
  
  

Regards,

Hieu

[Jerry Easley]

Hi Hieu,

Your response is very helpful; thank you so much!

Regards,

Jerry

[Hieu]

Hi Jerry,

Thank you for the kind words. It's good to know I was able to help

Regards,

Hieu