cmake: kconfig: auto-generate boolean board revision option

Automatically generate a boolean CONFIG_BOARD_REVISION_FOO=y Kconfig
option based on e.g. CONFIG_BOARD_REVISION="foo".

Signed-off-by: Chris Friedt <cfriedt@tenstorrent.com>

Author: cfriedt

cmake/modules/kconfig.cmake

@@ -66,6 +66,14 @@ if(DEFINED BOARD_REVISION)
     message(DEPRECATION "Use of '${board_rev_file}.conf' is deprecated, please switch to '${board_rev_file}_defconfig'")
     set_ifndef(BOARD_REVISION_CONFIG ${BOARD_DIR}/${board_rev_file}.conf)
   endif()
+
+  # Generate boolean board revision kconfig option
+  zephyr_string(SANITIZE TOUPPER BOARD_REVISION_GEN_CONFIG_VAR "BOARD_REVISION_${BOARD_REVISION}")
+
+  file(APPEND ${KCONFIG_BOARD_DIR}/Kconfig
+       "config ${BOARD_REVISION_GEN_CONFIG_VAR}\n"
+       "\tdef_bool y\n"
+  )
 endif()
 
 set(DOTCONFIG                  ${PROJECT_BINARY_DIR}/.config)

scripts/ci/check_compliance.py

@@ -971,7 +971,8 @@ def check_no_undef_outside_kconfig(self, kconf):
                 sym_name = sym_name[len(self.CONFIG_):]  # Strip CONFIG_
                 if sym_name not in defined_syms and \
                    sym_name not in self.UNDEF_KCONFIG_ALLOWLIST and \
-                   not (sym_name.endswith("_MODULE") and sym_name[:-7] in defined_syms):
+                   not (sym_name.endswith("_MODULE") and sym_name[:-7] in defined_syms) \
+                   and not sym_name.startswith("BOARD_REVISION_"):
 
                     undef_to_locs[sym_name].append(f"{path}:{lineno}")