cmake: kconfig: allow for Kconfig CONFIG namespace

This commit allows for specifying a dedicated Kconfig namespace, for
example: <namespace>_CONFIG

This namespace will then be used for handling loading of configuration
files into CMake configure scope, as well as handling of CMake cache
variables when set using `-D<namespace>_CONFIG_<var>=<value>`.

This allows greater flexibility when re-using the cmake/kconfig.cmake
in other projects.

Signed-off-by: Torsten Rasmussen <[email protected]>

Author: tejlmand

cmake/modules/kconfig.cmake

@@ -17,6 +17,8 @@ set_property(DIRECTORY APPEND PROPERTY CMAKE_CONFIGURE_DEPENDS ${AUTOCONF_H})
 file(MAKE_DIRECTORY ${PROJECT_BINARY_DIR}/kconfig/include/generated)
 file(MAKE_DIRECTORY ${PROJECT_BINARY_DIR}/kconfig/include/config)
 
+set_ifndef(KCONFIG_NAMESPACE "CONFIG")
+
 # Support multiple SOC_ROOT, remove ZEPHYR_BASE as that is always sourced.
 set(kconfig_soc_root ${SOC_ROOT})
 list(REMOVE_ITEM kconfig_soc_root ${ZEPHYR_BASE})
@@ -109,6 +111,7 @@ set(COMMON_KCONFIG_ENV_SETTINGS
   PYTHON_EXECUTABLE=${PYTHON_EXECUTABLE}
   srctree=${ZEPHYR_BASE}
   KERNELVERSION=${KERNELVERSION}
+  CONFIG_=${KCONFIG_NAMESPACE}_
   KCONFIG_CONFIG=${DOTCONFIG}
   # Set environment variables so that Kconfig can prune Kconfig source
   # files for other architectures
@@ -170,15 +173,15 @@ foreach(kconfig_target
 endforeach()
 
 # Support assigning Kconfig symbols on the command-line with CMake
-# cache variables prefixed with 'CONFIG_'. This feature is
-# experimental and undocumented until it has undergone more
+# cache variables prefixed according to the Kconfig namespace.
+# This feature is experimental and undocumented until it has undergone more
 # user-testing.
 unset(EXTRA_KCONFIG_OPTIONS)
 get_cmake_property(cache_variable_names CACHE_VARIABLES)
 foreach (name ${cache_variable_names})
-  if("${name}" MATCHES "^CONFIG_")
-    # When a cache variable starts with 'CONFIG_', it is assumed to be
-    # a Kconfig symbol assignment from the CMake command line.
+  if("${name}" MATCHES "^${KCONFIG_NAMESPACE}_")
+    # When a cache variable starts with the 'KCONFIG_NAMESPACE' value, it is
+    # assumed to be a Kconfig symbol assignment from the CMake command line.
     set(EXTRA_KCONFIG_OPTIONS
       "${EXTRA_KCONFIG_OPTIONS}\n${name}=${${name}}"
       )
@@ -316,18 +319,18 @@ add_custom_target(config-twister DEPENDS ${DOTCONFIG})
 # CMakeCache.txt. If the symbols end up in DOTCONFIG they will be
 # re-introduced to the namespace through 'import_kconfig'.
 foreach (name ${cache_variable_names})
-  if("${name}" MATCHES "^CONFIG_")
+  if("${name}" MATCHES "^${KCONFIG_NAMESPACE}_")
     unset(${name})
     unset(${name} CACHE)
   endif()
 endforeach()
 
-# Parse the lines prefixed with CONFIG_ in the .config file from Kconfig
-import_kconfig(CONFIG_ ${DOTCONFIG})
+# Import the .config file and make all settings available in CMake processing.
+import_kconfig(${KCONFIG_NAMESPACE} ${DOTCONFIG})
 
 # Re-introduce the CLI Kconfig symbols that survived
 foreach (name ${cache_variable_names})
-  if("${name}" MATCHES "^CONFIG_")
+  if("${name}" MATCHES "^${KCONFIG_NAMESPACE}_")
     if(DEFINED ${name})
       set(${name} ${${name}} CACHE STRING "")
     endif()