doc: confusion about dtc version

[andrewboie]

I set up a workstation with Ubuntu 18.04 LTS and discovered that the device-tree-compiler is out of date:

CMake Error at /home/apboie/projects/zephyr/zephyr/cmake/extensions.cmake:1111 (message):
  Assertion failed: The detected dtc version is unsupported.

      The version was found to be 1.4.5
      But the minimum supported version is 1.4.6
      See https://docs.zephyrproject.org/latest/getting_started/
      for how to use the SDK's dtc alongside a custom toolchain.

However, the provided link gives no information about using an alternate dtc binary. I have the Zephyr SDK 0.10 set up.

[andrewboie]

The SDK supposedly has a binary, but I can't seem to get the build to use it. If I do "sudo apt remove device-tree-compiler" it removes it, and then I get this when I try to build:

      The version was found to be 0.5.7
      But the minimum supported version is 1.4.6

I don't know where it is getting this 0.5.7 version of dtc

[carlescufi]

The SDK supposedly has a binary, but I can't seem to get the build to use it

Strange, this works perfectly well for me. I have dtc 1.4.5 in my system, but the build correctly uses the one in my SDK:

$ ~/bin/zephyr-sdk/sysroots/x86_64-pokysdk-linux/usr/bin/dtc --version
Version: DTC 1.4.7-g78e113e8-dirty

@andrewboie note that you need to set:
ZEPHYR_SDK_INSTALL_DIR="/home/carles/bin/zephyr-sdk"
for the build system to find your dtc.

This is documented here:

https://docs.zephyrproject.org/latest/getting_started/index.html#set-up-a-toolchain

If you want, you can use the SDK host tools (such as OpenOCD) with a different toolchain by keeping the ZEPHYR_SDK_INSTALL_DIR environment variable set to the Zephyr SDK installation directory, while setting ZEPHYR_TOOLCHAIN_VARIANT appropriately for a non-SDK toolchain.

It doesn't mention dtc, but the concept is documented.

[andrewboie]

I have ZEPHYR_SDK_INSTALL_DIR set, but it still couldn't find it.
I had to download dtc manually compile and install it. Then I was able to run sanitycheck.

[carlescufi]

@andrewboie I am puzzled then because it should search first CMAKE_PREFIX_PATH and then PATH. And it is being added to CMAKE_PREFIX_PATH according to:
https://github.com/zephyrproject-rtos/zephyr/blob/master/cmake/toolchain/zephyr/0.10.0/host-tools.cmake#L9

Can you please double-check that your ZEPHYR_SDK_INSTALL_DIR is pointing to a correct installation of 0.10.0?

[galak]

@andrewboie do you happen to have DTC set in your environment?

[carlescufi]

@andrewboie do you happen to have DTC set in your environment?

I thought about that but even then find_program should give precedence to the CMAKE_PREFIX_PATH according to CMake doc.

[andrewboie]

This must have something weird but transitory in my environment when I was setting up this workstation, seems to be fine now. Sorry for the noise!