makefiles: Add Kconfig related targets and dependencies

- The autoconf.h header file, generated with the current Kconfig
  configurations, is added as a build dependency.

- autoconf.h depends on the proper tool (genconfig) and a Kconfig.dep
  which contains the dependencies for the given application and board,
  this is generated from $(USEMODULE).

- The menuconfig target is added, to allow the configuration of modules
  using the Kconfig system.

Makefile.base

@@ -96,19 +96,19 @@ CCASFLAGS = $(filter-out $(CCASUWFLAGS), $(CFLAGS)) $(CCASEXFLAGS)
 
 $(OBJC_LTO): CFLAGS+=$(LTOFLAGS)
 
-$(OBJC): $(BINDIR)/$(MODULE)/%.o: %.c $(RIOTBUILD_CONFIG_HEADER_C)
+$(OBJC): $(BINDIR)/$(MODULE)/%.o: %.c $(RIOTBUILD_CONFIG_HEADER_C) $(KCONFIG_GENERATED_AUTOCONF_HEADER_C)
 	$(Q)$(CCACHE) $(CC) \
 		-DRIOT_FILE_RELATIVE=\"$(patsubst $(RIOTBASE)/%,%,$(abspath $<))\" \
 		-DRIOT_FILE_NOPATH=\"$(notdir $<)\" \
 		$(CFLAGS) $(INCLUDES) -MQ '$@' -MD -MP -c -o $@ $(abspath $<)
 
-$(GENOBJC): %.o: %.c $(RIOTBUILD_CONFIG_HEADER_C)
+$(GENOBJC): %.o: %.c $(RIOTBUILD_CONFIG_HEADER_C) $(KCONFIG_GENERATED_AUTOCONF_HEADER_C)
 	$(Q) $(CCACHE) $(CC) \
 		-DRIOT_FILE_RELATIVE=\"$(patsubst $(RIOTBASE)/%,%,$<)\" \
 		-DRIOT_FILE_NOPATH=\"$(notdir $<)\" \
 		$(CFLAGS) $(INCLUDES) -MQ '$@' -MD -MP -c -o $@ $<
 
-$(OBJCXX): $(BINDIR)/$(MODULE)/%.o: %.cpp $(RIOTBUILD_CONFIG_HEADER_C)
+$(OBJCXX): $(BINDIR)/$(MODULE)/%.o: %.cpp $(RIOTBUILD_CONFIG_HEADER_C) $(KCONFIG_GENERATED_AUTOCONF_HEADER_C)
 	$(Q)$(CCACHE) $(CXX) \
 		-DRIOT_FILE_RELATIVE=\"$(patsubst $(RIOTBASE)/%,%,$(abspath $<))\" \
 		-DRIOT_FILE_NOPATH=\"$(notdir $<)\" \
@@ -117,7 +117,7 @@ $(OBJCXX): $(BINDIR)/$(MODULE)/%.o: %.cpp $(RIOTBUILD_CONFIG_HEADER_C)
 $(ASMOBJ): $(BINDIR)/$(MODULE)/%.o: %.s
 	$(Q)$(AS) $(ASFLAGS) -o $@ $(abspath $<)
 
-$(ASSMOBJ): $(BINDIR)/$(MODULE)/%.o: %.S $(RIOTBUILD_CONFIG_HEADER_C)
+$(ASSMOBJ): $(BINDIR)/$(MODULE)/%.o: %.S $(RIOTBUILD_CONFIG_HEADER_C) $(KCONFIG_GENERATED_AUTOCONF_HEADER_C)
 	$(Q)$(CCAS) $(CCASFLAGS) $(INCLUDES) -MQ '$@' -MD -MP -c -o $@ $(abspath $<)
 
 # pull in dependency info for *existing* .o files

Makefile.include

@@ -148,6 +148,9 @@ include $(RIOTMAKE)/scan-build.inc.mk
 
 export RIOTBUILD_CONFIG_HEADER_C = $(BINDIR)/riotbuild/riotbuild.h
 
+# Include Kconfig functionalities
+include $(RIOTMAKE)/kconfig.mk
+
 ifeq ($(OS),Darwin)
   OPEN   := open
 else

makefiles/kconfig.mk

@@ -0,0 +1,88 @@
+# This is the root Kconfig
+KCONFIG ?= $(RIOTBASE)/Kconfig
+
+# Include tools targets
+include $(RIOTMAKE)/tools/kconfiglib.inc.mk
+
+# Generated dir will contain Kconfig generated configurations
+GENERATED_DIR = $(BINDIR)/generated
+
+# This file will contain all generated configuration from kconfig
+export KCONFIG_GENERATED_AUTOCONF_HEADER_C = $(GENERATED_DIR)/autoconf.h
+
+# Add configuration header to build dependencies
+BUILDDEPS += $(KCONFIG_GENERATED_AUTOCONF_HEADER_C)
+
+# Include configuration header when building
+CFLAGS += -include '$(KCONFIG_GENERATED_AUTOCONF_HEADER_C)'
+
+# Header for the generated header file
+define KCONFIG_AUTOHEADER_HEADER
+/* RIOT Configuration File */
+
+endef
+export KCONFIG_AUTOHEADER_HEADER
+
+# This file will contain the calculated dependencies formated in Kconfig
+export KCONFIG_GENERATED_DEPENDENCIES = $(GENERATED_DIR)/Kconfig.dep
+
+# This file will contain application default configurations
+KCONFIG_APP_CONFIG = $(APPDIR)/app.config
+
+# Default and user overwritten configurations
+KCONFIG_USER_CONFIG = $(APPDIR)/user.config
+
+# This file will contain merged configurations from MERGE_SOURCES and is the
+# one that is used to generate the 'riotconf.h' header
+KCONFIG_MERGED_CONFIG = $(GENERATED_DIR)/merged.config
+
+# Flag that indicates that the configuration has been edited
+KCONFIG_EDITED_CONFIG = $(GENERATED_DIR)/.editedconfig
+
+# Add configurations to merge, in ascendent priority (i.e. a file overrides the
+# previous ones)
+MERGE_SOURCES += $(wildcard $(KCONFIG_APP_CONFIG))
+MERGE_SOURCES += $(wildcard $(KCONFIG_USER_CONFIG))
+
+# Create directory to place generated files
+$(GENERATED_DIR): $(CLEAN)
+	$(Q)mkdir -p $@
+
+# Build a Kconfig file defining all used modules. This is done by defining
+# symbols like 'MODULE_<MODULE_NAME>' which default to 'y'. Then, every module
+# Kconfig menu will depend on that symbol being set to show its options.
+$(KCONFIG_GENERATED_DEPENDENCIES): FORCE | $(GENERATED_DIR)
+	$(Q)printf "%s " $(USEMODULE) \
+	  | awk 'BEGIN {RS=" "}{ gsub("-", "_", $$0); \
+	      printf "config MODULE_%s\n\tbool\n\tdefault y\n", toupper($$0)}' \
+	  | $(LAZYSPONGE) $(LAZYSPONGE_FLAGS) $@
+
+.PHONY: menuconfig
+
+# Opens the menuconfig interface for configuration of modules using the Kconfig
+# system.
+menuconfig: $(MENUCONFIG) $(KCONFIG_MERGED_CONFIG) $(KCONFIG_EDITED_CONFIG)
+	$(Q)KCONFIG_CONFIG=$(KCONFIG_MERGED_CONFIG) $(MENUCONFIG) $(KCONFIG)
+
+# Marks that the configuration file has been edited via some interface, such as
+# menuconfig
+$(KCONFIG_EDITED_CONFIG): FORCE
+	$(Q)touch $(KCONFIG_EDITED_CONFIG)
+
+# Generates a merged configuration file from the given sources. If the config
+# file has been edited a '.editedconfig' file will be present.
+# This is used to decide if the sources have to be merged or not.
+$(KCONFIG_MERGED_CONFIG): $(MERGECONFIG) $(KCONFIG_GENERATED_DEPENDENCIES) FORCE
+	$(Q)\
+	if ! test -f $(KCONFIG_EDITED_CONFIG); then \
+	  if ! test -z "$(strip $(MERGE_SOURCES))"; then \
+	    $(MERGECONFIG) $(KCONFIG) $@ $(MERGE_SOURCES); \
+	  else \
+	    rm -f $@; \
+	  fi \
+	fi
+
+# Build a header file with all the Kconfig configurations. genconfig will avoid
+# any unnecessary rewrites of the header file if no configurations changed.
+$(KCONFIG_GENERATED_AUTOCONF_HEADER_C): $(KCONFIG_GENERATED_DEPENDENCIES) $(GENCONFIG) $(KCONFIG_MERGED_CONFIG) FORCE
+	$(Q)KCONFIG_CONFIG=$(KCONFIG_MERGED_CONFIG) $(GENCONFIG) --header-path $@ $(KCONFIG)