Simplify the PLATFORM/CONFIG handling a little.

Makefile

@@ -29,6 +29,11 @@ RMDIR			 = rm -rf
 #
 CONFIGS			?= px4fmu_default px4io_default
 
+#
+# Platforms (boards) that we build NuttX export kits for.
+#
+PLATFORMS		 = px4fmu px4io
+
 #
 # If the user has listed a config as a target, strip it out and override CONFIGS
 #
@@ -39,16 +44,6 @@ CONFIGS			:= $(EXPLICIT_CONFIGS)
 $(EXPLICIT_CONFIGS):	all
 endif
 
-#
-# Platforms (boards) that we build prelink kits for.
-#
-PLATFORMS		 = px4fmu px4io
-
-#
-# Some handy macros
-#
-PLATFORM_FROM_CONFIG	 = $(word 1,$(subst _, ,$1))
-
 #
 # Built products
 #
@@ -72,7 +67,7 @@ $(STAGED_FIRMWARES): $(IMAGE_DIR)/%.px4: $(BUILD_DIR)/%.build/firmware.px4
 	$(Q) $(COPY) $< $@
 
 #
-# Generate FIRMWARES
+# Generate FIRMWARES.
 #
 $(BUILD_DIR)/%.build/firmware.px4: config   = $(patsubst $(BUILD_DIR)/%.build/firmware.px4,%,$@)
 $(BUILD_DIR)/%.build/firmware.px4: work_dir = $(BUILD_DIR)/$(config).build
@@ -81,8 +76,6 @@ $(FIRMWARES): $(BUILD_DIR)/%.build/firmware.px4:
 	$(Q) mkdir -p $(work_dir)
 	$(Q) make -C $(work_dir) \
 		-f $(PX4_BASE)/makefiles/$(config).mk \
-		CONFIG=$(config) \
-		PLATFORM=$(call PLATFORM_FROM_CONFIG,$(config)) \
 		WORK_DIR=$(work_dir)
 
 #

makefiles/firmware.mk

@@ -74,11 +74,15 @@ RMDIR			 = rm -rf
 
 #
 # Sanity-check the PLATFORM variable and then get the platform config.
+# If PLATFORM is not set, but CONFIG is, use that.
 #
 # The platform config in turn will fetch the toolchain configuration.
 #
 ifeq ($(PLATFORM),)
-$(error The PLATFORM variable must be set before including firmware.mk)
+ifeq ($(CONFIG),)
+$(error At least one of the PLATFORM or CONFIG variables must be set before including firmware.mk)
+endif
+PLATFORM		:= $(firstword $(subst _, ,$(CONFIG)))
 endif
 include $(PX4_MK_INCLUDE)/$(PLATFORM).mk
 

makefiles/px4fmu_default.mk

@@ -2,6 +2,7 @@
 # Makefile for the px4fmu_default configuration
 #
 
+CONFIG		 = px4fmu_default
 PLATFORM	 = px4fmu
 SRCS		 = $(PX4_BASE)/platforms/empty.c
 

makefiles/px4io_default.mk

@@ -2,6 +2,7 @@
 # Makefile for the px4io_default configuration
 #
 
+CONFIG		 = px4io_default
 PLATFORM	 = px4io
 SRCS		 = $(PX4_BASE)/platforms/empty.c