From aa40507997a0052c04856db1ad6f290eb1f727cb Mon Sep 17 00:00:00 2001
From: Jamie McCrae <jamie.mccrae@nordicsemi.no>
Date: Wed, 13 Nov 2024 12:58:56 +0000
Subject: [PATCH] [nrf fromlist] cmake: dts: Use temporary file for dts.cmake

Uses a temporary file for dts output then uses CMake to copy to the
correct file if it has changed. This prevents a ping-pong issue when
sysbuild is used of configuring and building cycle when nothing has
changed and there is sysbuild code which loads in the devicetree
data from an image

Upstream PR #: 81340

Signed-off-by: Jamie McCrae <jamie.mccrae@nordicsemi.no>
---
 cmake/modules/dts.cmake | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/cmake/modules/dts.cmake b/cmake/modules/dts.cmake
index 705de97d874..eb7869548fe 100644
--- a/cmake/modules/dts.cmake
+++ b/cmake/modules/dts.cmake
@@ -321,17 +321,26 @@ endif()
 #
 # Run GEN_DTS_CMAKE_SCRIPT.
 #
+# A temporary file is copied to the original file if it differs. This prevents issue such as a
+# cycle when sysbuild is used of configuring and building multiple times due to the dts.cmake file
+# of images having a newer modification time than the sysbuild build.ninja file, despite the
+# output having not changed
+#
+set(dts_cmake_tmp ${DTS_CMAKE}.new)
 
 execute_process(
   COMMAND ${PYTHON_EXECUTABLE} ${GEN_DTS_CMAKE_SCRIPT}
   --edt-pickle ${EDT_PICKLE}
-  --cmake-out ${DTS_CMAKE}
+  --cmake-out ${dts_cmake_tmp}
   WORKING_DIRECTORY ${PROJECT_BINARY_DIR}
   RESULT_VARIABLE ret
   )
 if(NOT "${ret}" STREQUAL "0")
   message(FATAL_ERROR "gen_dts_cmake.py failed with return code: ${ret}")
 else()
+  zephyr_file_copy(${dts_cmake_tmp} ${DTS_CMAKE} ONLY_IF_DIFFERENT)
+  file(REMOVE ${dts_cmake_tmp})
+  set(dts_cmake_tmp)
   message(STATUS "Including generated dts.cmake file: ${DTS_CMAKE}")
   include(${DTS_CMAKE})
 endif()