refactor(build): Fixes for config/overlay loading.

* Move to ZephyrBuildConfig package based on Zephyr best practices.
* Support multiple shields properly, e.g. -DSHIELD="foo bar", which
  allows using existing upstream shields like `ssd1306_128x64` along
  with another ZMK shield.
* Properly *add* the "ZMK config" .conf file to the conf file list,
  so that existing board .conf files in `app/boards/<board>.conf` are
  properly honored still. Needed for overrides to usptream boards when
  combined with a local `<shield>.conf` file.

app/CMakeLists.txt

@@ -1,18 +1,16 @@
 cmake_minimum_required(VERSION 3.13.1)
 
 set(CONFIG_APPLICATION_DEFINED_SYSCALL true)
-list(APPEND BOARD_ROOT ${CMAKE_SOURCE_DIR})
-list(APPEND DTS_ROOT ${CMAKE_SOURCE_DIR})
 
 # Add our custom Zephyr module for drivers w/ syscalls, etc.
 list(APPEND DTS_ROOT ${CMAKE_SOURCE_DIR}/drivers/zephyr)
 
+set(ZephyrBuildConfiguration_ROOT ${CMAKE_SOURCE_DIR}/cmake)
+
 list(APPEND ZEPHYR_EXTRA_MODULES
   ${CMAKE_CURRENT_SOURCE_DIR}/drivers
 )
 
-include(cmake/zmk_config.cmake)
-
 # Find Zephyr. This also loads Zephyr's build system.
 find_package(Zephyr REQUIRED HINTS ../zephyr)
 project(zmk)

app/cmake/ZephyrBuildConfig.cmake

@@ -7,6 +7,9 @@
 
 cmake_minimum_required(VERSION 3.15)
 
+list(APPEND BOARD_ROOT ${APPLICATION_SOURCE_DIR})
+list(APPEND DTS_ROOT ${APPLICATION_SOURCE_DIR})
+
 get_property(cached_user_config_value CACHE ZMK_CONFIG PROPERTY VALUE)
 
 set(user_config_cli_argument ${cached_user_config_value}) # Either new or old
@@ -57,9 +60,29 @@ if (ZMK_CONFIG)
 	endif()
 endif()
 
+
+if(DEFINED SHIELD)
+	string(REPLACE " " ";" SHIELD_AS_LIST "${SHIELD}")
+endif()
+
 foreach(root ${BOARD_ROOT})
+	set(shield_dir ${root}/boards/shields)
+	# Match the Kconfig.shield files in the shield directories to make sure we are
+	# finding shields, e.g. x_nucleo_iks01a1/Kconfig.shield
+	file(GLOB_RECURSE shields_refs_list ${shield_dir}/*/Kconfig.shield)
+	unset(SHIELD_LIST)
+	foreach(shields_refs ${shields_refs_list})
+		get_filename_component(shield_path ${shields_refs} DIRECTORY)
+		file(GLOB shield_overlays RELATIVE ${shield_path} ${shield_path}/*.overlay)
+		foreach(overlay ${shield_overlays})
+			get_filename_component(shield ${overlay} NAME_WE)
+			list(APPEND SHIELD_LIST ${shield})
+			set(SHIELD_DIR_${shield} ${shield_path})
+		endforeach()
+	endforeach()
+
 	if (EXISTS "${root}/boards/${BOARD}.overlay")
-		list(APPEND ZMK_DTC_FILES "${root}/boards/${BOARD}.overlay")
+		list(APPEND shield_dts_files "${root}/boards/${BOARD}.overlay")
 	endif()
 	if (NOT DEFINED BOARD_DIR_NAME)
 		find_path(BOARD_DIR
@@ -74,34 +97,58 @@ foreach(root ${BOARD_ROOT})
 	endif()
 
 	if(DEFINED SHIELD)
-		find_path(shields_refs_list
+		foreach(s ${SHIELD_AS_LIST})
-		    NAMES ${SHIELD}.overlay
+			if(NOT ${s} IN_LIST SHIELD_LIST)
-		    PATHS ${root}/boards/shields/*
+				message(WARNING "Didn't find ${s}")
-		    NO_DEFAULT_PATH
+				continue()
-		    )
+			endif()
-		foreach(shield_path ${shields_refs_list})
+			message(STATUS "Adding ${SHIELD_DIR_${s}}")
-			get_filename_component(SHIELD_DIR ${shield_path} NAME)
+			list(APPEND KEYMAP_DIRS ${SHIELD_DIR_${s}})
-			list(APPEND KEYMAP_DIRS ${shield_path})
+			get_filename_component(shield_dir_name ${SHIELD_DIR_${s}} NAME)
+			list(APPEND SHIELD_DIR ${shield_dir_name})
 		endforeach()
 	endif()
 endforeach()
 
+# Give a shield like `kyria_rev2_left` we want to use `kyria_rev2` and `kyria` as candidate names for
+# overlay/conf/keymap files.
+if(DEFINED SHIELD)
+	foreach(s ${SHIELD_AS_LIST})
+		message(STATUS ${SHIELD_DIR_${s}})
+		get_filename_component(shield_dir_name ${SHIELD_DIR_${s}} NAME)
+		string(REPLACE "_" ";" S_PIECES ${s})
+		list(LENGTH S_PIECES S_PIECES_LEN)
+		while(NOT S_PIECES STREQUAL "")
+			list(POP_BACK S_PIECES)
+			list(JOIN S_PIECES "_" S_SUBSTR)
+			if (S_SUBSTR STREQUAL ${shield_dir_name})
+				break()
+			endif()
+			list(APPEND shield_candidate_names ${S_SUBSTR})
+		endwhile()
+	endforeach()
+endif()
+
 if (ZMK_CONFIG)
 	if (EXISTS ${ZMK_CONFIG})
 		message(STATUS "ZMK Config directory: ${ZMK_CONFIG}")
 		list(APPEND DTS_ROOT ${ZMK_CONFIG})
 		list(PREPEND KEYMAP_DIRS "${ZMK_CONFIG}")
 
-		if (SHIELD)
+		if (DEFINED SHIELD)
-			message(STATUS "Board: ${BOARD}, ${BOARD_DIR}, ${SHIELD}, ${SHIELD_DIR}")
+			foreach (s ${shield_candidate_names})
-			list(APPEND overlay_candidates "${ZMK_CONFIG}/${SHIELD_DIR}.overlay")
+				if (DEFINED $SHIELD_DIR_${s})
-			list(APPEND overlay_candidates "${ZMK_CONFIG}/${SHIELD_DIR}_${BOARD}.overlay")
+					get_filename_component(shield_dir_name ${SHIELD_DIR_${s}} NAME)
-			list(APPEND overlay_candidates "${ZMK_CONFIG}/${SHIELD}_${BOARD}.overlay")
+				endif()
-			list(APPEND overlay_candidates "${ZMK_CONFIG}/${SHIELD}.overlay")
+				list(APPEND overlay_candidates "${ZMK_CONFIG}/${s}_${BOARD}.overlay")
-			list(APPEND config_candidates "${ZMK_CONFIG}/${SHIELD_DIR}.conf")
+				list(APPEND overlay_candidates "${ZMK_CONFIG}/${s}.overlay")
-			list(APPEND config_candidates "${ZMK_CONFIG}/${SHIELD_DIR}_${BOARD}.conf")
+				if (NOT "${shield_dir_name}" STREQUAL "${s}")
-			list(APPEND config_candidates "${ZMK_CONFIG}/${SHIELD}_${BOARD}.conf")
+					list(APPEND config_candidates "${ZMK_CONFIG}/${shield_dir_name}_${BOARD}.conf")
-			list(APPEND config_candidates "${ZMK_CONFIG}/${SHIELD}.conf")
+					list(APPEND config_candidates "${ZMK_CONFIG}/${shield_dir_name}.conf")
+				endif()
+				list(APPEND config_candidates "${ZMK_CONFIG}/${s}_${BOARD}.conf")
+				list(APPEND config_candidates "${ZMK_CONFIG}/${s}.conf")
+			endforeach()
 		endif()
 
 		# TODO: Board revisions?
@@ -115,7 +162,7 @@ if (ZMK_CONFIG)
 		foreach(overlay ${overlay_candidates})
 			if (EXISTS "${overlay}")
 				message(STATUS "ZMK Config devicetree overlay: ${overlay}")
-				list(APPEND ZMK_DTC_FILES "${overlay}")
+				list(APPEND shield_dts_files "${overlay}")
 				break()
 			endif()
 		endforeach()
@@ -123,8 +170,7 @@ if (ZMK_CONFIG)
 		foreach(conf ${config_candidates})
 			if (EXISTS "${conf}")
 				message(STATUS "ZMK Config Kconfig: ${conf}")
-				set(CONF_FILE "${conf}")
+				list(APPEND shield_conf_files "${conf}")
-				break()
 			endif()
 		endforeach()
 	else()
@@ -135,22 +181,20 @@ endif()
 
 if(NOT KEYMAP_FILE)
 	foreach(keymap_dir ${KEYMAP_DIRS})
-		foreach(keymap_prefix ${SHIELD} ${SHIELD_DIR} ${BOARD} ${BOARD_DIR_NAME})
+		foreach(keymap_prefix ${shield_candidate_names} ${SHIELD_AS_LIST} ${SHIELD_DIR} ${BOARD} ${BOARD_DIR_NAME})
 			if (EXISTS ${keymap_dir}/${keymap_prefix}.keymap)
 				set(KEYMAP_FILE "${keymap_dir}/${keymap_prefix}.keymap" CACHE STRING "Selected keymap file")
 				message(STATUS "Using keymap file: ${KEYMAP_FILE}")
+				set(DTC_OVERLAY_FILE ${KEYMAP_FILE})
 				break()
 			endif()
 		endforeach()
 	endforeach()
+else()
+	message(STATUS "Using keymap file: ${KEYMAP_FILE}")
+	set(DTC_OVERLAY_FILE ${KEYMAP_FILE})
 endif()
 
 if (NOT KEYMAP_FILE)
-	message(FATAL_ERROR "Failed to locate keymap file!")
+	message(WARNING "Failed to locate keymap file!")
-endif()
-
-list(APPEND ZMK_DTC_FILES ${KEYMAP_FILE})
-
-if (ZMK_DTC_FILES)
-	string(REPLACE ";" " " DTC_OVERLAY_FILE "${ZMK_DTC_FILES}")
 endif()