kbuild: allow empty board directories

U-Boot has compelled all boards to have
board/${BOARD}/ or board/${VENDOR}/${BOARD}/ directory.

Sometimes it does not seem suitable for some boards,
for example Sandbox. (Is it a board?)

And arcangel4 board has nothing to compile
under the board directory.

This commit makes the build system more flexible:
If '<none>' is given to the 6th column (=Board name) of boards.cfg,
Kbuild will not descend into the board directory.
Signed-off-by: NMasahiro Yamada <yamada.m@jp.panasonic.com>

Makefile

@@ -636,7 +636,7 @@ endif
 libs-$(CONFIG_ARM) += arch/arm/cpu/
 libs-$(CONFIG_PPC) += arch/powerpc/cpu/
 
-libs-y += board/$(BOARDDIR)/
+libs-y += $(if $(BOARDDIR),board/$(BOARDDIR)/)
 
 libs-y := $(sort $(libs-y))
 

config.mk

@@ -28,11 +28,13 @@ sinclude $(TOPDIR)/$(CPUDIR)/config.mk		# include  CPU	specific rules
 ifdef	SOC
 sinclude $(TOPDIR)/$(CPUDIR)/$(SOC)/config.mk	# include  SoC	specific rules
 endif
+ifneq ($(BOARD),)
 ifdef	VENDOR
 BOARDDIR = $(VENDOR)/$(BOARD)
 else
 BOARDDIR = $(BOARD)
 endif
+endif
 ifdef	BOARD
 sinclude $(TOPDIR)/board/$(BOARDDIR)/config.mk	# include board specific rules
 endif

mkconfig

@@ -55,7 +55,9 @@ CONFIG_NAME="${7%_config}"
 arch="$2"
 cpu=`echo $3 | awk 'BEGIN {FS = ":"} ; {print $1}'`
 spl_cpu=`echo $3 | awk 'BEGIN {FS = ":"} ; {print $2}'`
-if [ "$6" = "-" ] ; then
+if [ "$6" = "<none>" ] ; then
+	board=
+elif [ "$6" = "-" ] ; then
 	board=${BOARD_NAME}
 else
 	board="$6"
@@ -177,8 +179,8 @@ echo "#define CONFIG_SYS_BOARD \"${board}\"" >> config.h
 
 [ "${soc}"    ] && echo "#define CONFIG_SYS_SOC    \"${soc}\""    >> config.h
 
+[ "${board}"  ] && echo "#define CONFIG_BOARDDIR board/$BOARDDIR" >> config.h
 cat << EOF >> config.h
-#define CONFIG_BOARDDIR board/$BOARDDIR
 #include <config_cmd_defaults.h>
 #include <config_defaults.h>
 #include <configs/${CONFIG_NAME}.h>