Draft: External cpu dir

Makefile.dep

@@ -11,7 +11,7 @@ endif
 -include $(BOARDDIR)/Makefile.dep
 
 # include cpu dependencies
--include $(RIOTCPU)/$(CPU)/Makefile.dep
+-include $(CPUDIR)/Makefile.dep
 
 # include external modules dependencies
 # processed before RIOT ones to be evaluated before the 'default' rules.

Makefile.features

@@ -19,7 +19,23 @@ ifeq (,$(CPU))
   $(error $(BOARD): CPU must be defined by board / board_common Makefile.features)
 endif
 
-include $(RIOTCPU)/$(CPU)/Makefile.features
+CPUSDIRS := $(EXTERNAL_CPU_DIRS) $(RIOTCPU)
+
+# Take the first folder in $(CPUSDIRS) that contains a folder named $(CPU)
+CPUDIR := $(word 1,$(foreach dir,$(CPUSDIRS),$(wildcard $(dir)/$(CPU)/.)))
+# Sanitize folder
+CPUDIR := $(abspath $(CPUDIR))
+
+# Also provide CPUSDIR for compatibility and for accessing common folders
+# (e.g. include $(CPUSDIR)/common/external_common/Makefile.dep)
+CPUSDIR := $(dir $(CPUDIR))
+
+ifeq (,$(CPUDIR))
+  $(info Folders searched for the cpu: $(CPUSDIRS))
+  $(error The specified cpu $(CPU) does not exist.)
+endif
+
+include $(CPUDIR)/Makefile.features
 
 # Provide CPU as a feature to allow listing all boards with a CPU
 FEATURES_PROVIDED += cpu_$(CPU)

Makefile.include

@@ -43,6 +43,7 @@ include $(RIOT_MAKEFILES_GLOBAL_PRE)
 # set undefined variables
 RIOTBASE                        ?= $(_riotbase)
 RIOTCPU                         ?= $(RIOTBASE)/cpu
+EXTERNAL_CPU_DIRS               ?=
 # Deprecated to set RIOTBOARD, use EXTERNAL_BOARD_DIRS
 RIOTBOARD                       ?= $(RIOTBASE)/boards
 EXTERNAL_BOARD_DIRS             ?=
@@ -106,6 +107,9 @@ ifeq ($(INSIDE_DOCKER),0)
   ifeq ($(origin EXTERNAL_PKG_DIRS),command line)
     $(error EXTERNAL_PKG_DIRS must be passed as environment variable, and not as command line argument)
   endif
+  ifeq ($(origin EXTERNAL_CPU_DIRS),command line)
+    $(error EXTERNAL_CPU_DIRS must be passed as environment variable, and not as command line argument)
+  endif
 endif
 
 # Deprecation of configuring 'RIOTBOARD'
@@ -152,6 +156,9 @@ EXTERNAL_MODULE_DIRS            := $(foreach dir,\
 EXTERNAL_PKG_DIRS               := $(foreach dir,\
                                              $(EXTERNAL_PKG_DIRS),\
                                              $(abspath $(dir)))
+EXTERNAL_CPU_DIRS               := $(foreach dir,\
+                                             $(EXTERNAL_CPU_DIRS),\
+                                             $(abspath $(dir)))
 
 # Ensure that all directories are set and don't contain spaces.
 ifneq (, $(filter-out 1, $(foreach v,$(__DIRECTORY_VARIABLES),$(words $($(v))))))
@@ -425,8 +432,8 @@ include $(RIOTMAKE)/boot/riotboot_dfu-util.mk
 # Include Board and CPU configuration
 INCLUDES += $(addprefix -I,$(wildcard $(BOARDDIR)/include))
 include $(BOARDDIR)/Makefile.include
-INCLUDES += -I$(RIOTCPU)/$(CPU)/include
-include $(RIOTCPU)/$(CPU)/Makefile.include
+INCLUDES += -I$(CPUDIR)/include
+include $(CPUDIR)/Makefile.include
 
 # include global Makefile.include for `boards` modules
 include $(RIOTBASE)/boards/Makefile.include

makefiles/application.inc.mk

@@ -1,6 +1,6 @@
 MODULE = $(APPLICATION_MODULE)
 
-DIRS += $(RIOTCPU)/$(CPU) $(BOARDDIR)
+DIRS += $(CPUDIR) $(BOARDDIR)
 DIRS += $(RIOTBASE)/boards
 DIRS += $(RIOTBASE)/core $(RIOTBASE)/core/lib $(RIOTBASE)/drivers $(RIOTBASE)/sys
 

makefiles/defaultmodules_regular.inc.mk

@@ -12,4 +12,4 @@ DEFAULT_MODULE += board board_common_init \
 -include $(BOARDDIR)/Makefile.default
 
 # Include potentially added default modules by the CPU
--include $(RIOTCPU)/$(CPU)/Makefile.default
+-include $(CPUDIR)/Makefile.default

makefiles/dependency_resolution.inc.mk

@@ -74,6 +74,7 @@ else
 
   # Detect provided / used / optional features that do not exist
   include $(RIOTMAKE)/features_existing.inc.mk
+  -include $(EXTERNAL_CPU_DIRS)/features_existing.inc.mk
   FEATURES_NONEXISTING := $(sort $(filter-out $(FEATURES_EXISTING),$(FEATURES_PROVIDED)))
   ifneq (,$(FEATURES_NONEXISTING))
     $(error "The following non-existing features are provided by the board $(BOARD): $(FEATURES_NONEXISTING)")

makefiles/info.inc.mk

@@ -43,6 +43,7 @@ info-build:
 	@echo 'RIOTBASE:    $(RIOTBASE)'
 	@echo 'BOARDDIR:    $(BOARDDIR)'
 	@echo 'EXTERNAL_BOARD_DIRS:$(EXTERNAL_BOARD_DIRS)'
+	@echo 'EXTERNAL_CPU_DIRS:$(EXTERNAL_CPU_DIRS)'
 	@echo 'RIOTCPU:     $(RIOTCPU)'
 	@echo 'RIOTPKG:     $(RIOTPKG)'
 	@echo ''

makefiles/vars.inc.mk

@@ -39,6 +39,9 @@ export RIOTBOARD             # This folder is the base of the riot boards.
 export BOARDSDIR             # This is the folder containing the board dir
 export EXTERNAL_BOARD_DIRS   # List of folders containing external board dirs
 export BOARDDIR              # This folder contains the board
+export CPUSDIR               # This is the folder containing the CPU dir
+export EXTERNAL_CPU_DIRS     # list of folders containing external CPU dirs
+export CPUDIR                # This folder contains the CPU
 export RIOTPKG               # For overriding RIOT's pkg directory
 export RIOTTOOLS             # Location of host machine tools
 export RIOTPROJECT           # Top level git root of the project being built, or PWD if not a git repository