Makefile: prepare for using Kbuild-style Makefile

Every makefile in sub directories has common lines
at the top and the bottom.
This commit pushes the common parts into script/Makefile.build.

Going forward sub-makefiles only need to describe this part:

    COBJS := ...
    COBJS += ...
    SOBJS := ...

But using obj-y is preferable to prepare for switching to Kbuild.

The conventional (non-Kbuild) Makefile style is still supported.
This is achieved by greping the Makefile before entering into it.
U-Boot conventional sub makefiles always include some other makefiles.
So the build system searches a line beginning with "include" keyword
in the makefile in order to distinguish which style it is.
If the Makefile include a "include" line, we assume it is a conventional
U-Boot style. Otherwise, it is treated as a Kbuild-style makefile.

With this tweak, we can switch sub-makefiles
from U-Boot style to Kbuild style little by little.

obj-y := foo/
syntax (descending into the sub directory) is not supportd yet.
It will be implemented in the upcomming commit.

Signed-off-by: Masahiro Yamada <yamada.m@jp.panasonic.com>
Cc: Simon Glass <sjg@chromium.org>
Cc: Tom Rini <trini@ti.com>

1 files changed, 48 insertions, 0 deletions

diff --git a/scripts/Makefile.build b/scripts/Makefile.build
new file mode 100644
index 00000000000..f969ec55bde
--- /dev/null
+++ b/scripts/Makefile.build
@@ -0,0 +1,48 @@
+# our default target
+.PHONY: all
+all:
+
+include $(TOPDIR)/config.mk
+
+LIB := $(obj)built-in.o
+LIBGCC = $(obj)libgcc.o
+SRCS :=
+
+include Makefile
+
+# Backward compatible: obj-y is preferable
+COBJS := $(sort $(COBJS) $(COBJS-y))
+SOBJS := $(sort $(SOBJS) $(SOBJS-y))
+
+# Going forward use the following
+obj-y := $(sort $(obj-y))
+extra-y := $(sort $(extra-y))
+lib-y := $(sort $(lib-y))
+
+SRCS	+= $(COBJS:.o=.c) $(SOBJS:.o=.S) \
+ $(wildcard $(obj-y:.o=.c) $(obj-y:.o=.S) $(lib-y:.o=.c) $(lib-y:.o=.S) $(extra-y:.o=.c) $(extra-y:.o=.S))
+OBJS	:= $(addprefix $(obj),$(COBJS) $(SOBJS) $(obj-y))
+
+LGOBJS := $(addprefix $(obj),$(sort $(GLSOBJS) $(GLCOBJS)) $(lib-y))
+
+all: $(LIB) $(addprefix $(obj),$(extra-y))
+
+$(LIB):	$(obj).depend $(OBJS)
+	$(call cmd_link_o_target, $(OBJS))
+
+ifneq ($(strip $(lib-y)),)
+all: $(LIBGCC)
+
+$(LIBGCC): $(obj).depend $(LGOBJS)
+	$(call cmd_link_o_target, $(LGOBJS))
+endif
+
+#########################################################################
+
+# defines $(obj).depend target
+
+include $(TOPDIR)/rules.mk
+
+sinclude $(obj).depend
+
+#########################################################################