Device tree overlays and non-secure app headers

[Louis]

I have a non-secure app targeted at the nRF9160-DK platform and use SPM as the secure app. I can apply a device tree overlay to SPM to enable peripherals from the non-secure development workspace by setting spm_DTC_OVERLAY_FILE at the beginning of CMakeLists.txt

set(spm_DTC_OVERLAY_FILE ${CMAKE_CURRENT_SOURCE_DIR}/spm/nrf9160_pca10090.overlay) 

Problem is that the SPM device tree overlay is ignored by the generated headers files of the non-secure app (build/zephyr/include/generated/devicetree_*.h). Is there a way to add an overlay to zephyr/boards/arm/nrf9160_pca10090/nrf9160_pca10090_common.dts from the non-secure development workspace and that will apply to the generated headers files? The only way I found is to actually use the non-secure overlay as the SPM overlay:

set(spm_DTC_OVERLAY_FILE ${CMAKE_CURRENT_SOURCE_DIR}/nrf9160_pca10090ns.overlay)

Is there a better way? Thanks.

[Simonr]

Hi Louis

Please check out the DeviceTree Definitions in the Zephyr documentation which explains out of tree DTS in general. Please note that the structure that's proposed here has to be right after the CMakeLists that describes your project.

Best regards,

Simon

[Louis]

Thanks Simon,

I believe that what I did is consistent with the zephyr documentation however it feels like a hack and the documentation doesn't specify how to apply an overlay to a device tree upstream, just how to apply an overlay to the board's device tree. The issue here is specific to the dual application (non-secure user app and secure SPM) .

[Simonr]

Hi Louis

Sorry for not pointing to this straight away, but our NCS tutorial Part 2, has a section regarding modifying the Device tree and configurations of a child image, using the SPM in specific as an example. I think you should find it helpful.

Best regards,

Simon