kbuild: change out-of-tree build

This commit changes the working directory
where the build process occurs.

Before this commit, build process occurred under the source
tree for both in-tree and out-of-tree build.

That's why we needed to add $(obj) prefix to all generated
files in makefiles like follows:
  $(obj)u-boot.bin:  $(obj)u-boot

Here, $(obj) is empty for in-tree build, whereas it points
to the output directory for out-of-tree build.

And our old build system changes the current working directory
with "make -C <sub-dir>" syntax when descending into the
sub-directories.

On the other hand, Kbuild uses a different idea
to handle out-of-tree build and directory descending.

The build process of Kbuild always occurs under the output tree.
When "O=dir/to/store/output/files" is given, the build system
changes the current working directory to that directory and
restarts the make.

Kbuild uses "make -f $(srctree)/scripts/Makefile.build obj=<sub-dir>"
syntax for descending into sub-directories.
(We can write it like "make $(obj)=<sub-dir>" with a shorthand.)
This means the current working directory is always the top
of the output directory.

Signed-off-by: Masahiro Yamada <yamada.m@jp.panasonic.com>
Tested-by: Gerhard Sittig <gsi@denx.de>

2 files changed, 15 insertions, 15 deletions

diff --git a/examples/api/Makefile b/examples/api/Makefile
index ee3c487c13..db0bb34afe 100644
--- a/examples/api/Makefile
+++ b/examples/api/Makefile
@@ -40,23 +40,23 @@ SRCS	+= $(addprefix $(SRCTREE)/examples/api/,$(COBJ_FILES-y:.o=.c))
 SRCS	+= $(addprefix $(SRCTREE)/examples/api/,$(SOBJ_FILES-y:.o=.S))
 
 # Create a list of object files to be compiled
-OBJS	+= $(addprefix $(obj),$(SOBJ_FILES-y))
-OBJS	+= $(addprefix $(obj),$(COBJ_FILES-y))
-OBJS	+= $(addprefix $(obj),$(notdir $(EXT_COBJ_FILES-y)))
-OBJS	+= $(addprefix $(obj),$(notdir $(EXT_SOBJ_FILES-y)))
+OBJS	+= $(addprefix $(obj)/,$(SOBJ_FILES-y))
+OBJS	+= $(addprefix $(obj)/,$(COBJ_FILES-y))
+OBJS	+= $(addprefix $(obj)/,$(notdir $(EXT_COBJ_FILES-y)))
+OBJS	+= $(addprefix $(obj)/,$(notdir $(EXT_SOBJ_FILES-y)))
 
 #########################################################################
 
-$(obj)demo:	$(OBJS)
+$(obj)/demo:	$(OBJS)
 		$(LD) --gc-sections -Ttext $(LOAD_ADDR) -o $@ $^ $(PLATFORM_LIBS)
 
-$(obj)demo.bin: $(obj)demo
+$(obj)/demo.bin: $(obj)/demo
 		$(OBJCOPY) -O binary $< $@ 2>/dev/null
 
 # Rule to build generic library C files
-$(addprefix $(obj),$(notdir $(EXT_COBJ_FILES-y))): $(obj)%.o: $(SRCTREE)/lib/%.c
+$(addprefix $(obj)/,$(notdir $(EXT_COBJ_FILES-y))): $(obj)/%.o: $(SRCTREE)/lib/%.c
 	$(CC) -g $(CFLAGS) -c -o $@ $<
 
 # Rule to build architecture-specific library assembly files
-$(addprefix $(obj),$(notdir $(EXT_SOBJ_FILES-y))): $(obj)%.o: $(SRCTREE)/arch/$(ARCH)/lib/%.S
+$(addprefix $(obj)/,$(notdir $(EXT_SOBJ_FILES-y))): $(obj)/%.o: $(SRCTREE)/arch/$(ARCH)/lib/%.S
 	$(CC) -g $(CFLAGS) -c -o $@ $<
diff --git a/examples/standalone/Makefile b/examples/standalone/Makefile
index 1f8d70ce8a..a6819f7792 100644
--- a/examples/standalone/Makefile
+++ b/examples/standalone/Makefile
@@ -31,7 +31,7 @@ clean-files  := $(extra-) $(addsuffix .srec,$(extra-)) $(addsuffix .bin,$(extra-
 
 COBJS	:= $(ELF:=.o)
 
-LIB	= $(obj)libstubs.o
+LIB	= $(obj)/libstubs.o
 
 LIBAOBJS-$(CONFIG_PPC) += ppc_longjmp.o ppc_setjmp.o
 LIBAOBJS-$(CONFIG_8xx) += test_burst_lib.o
@@ -39,11 +39,11 @@ LIBAOBJS := $(LIBAOBJS-y)
 
 LIBCOBJS = stubs.o
 
-LIBOBJS	= $(addprefix $(obj),$(LIBAOBJS) $(LIBCOBJS))
+LIBOBJS	= $(addprefix $(obj)/,$(LIBAOBJS) $(LIBCOBJS))
 
 SRCS	:= $(COBJS:.o=.c) $(LIBCOBJS:.o=.c) $(LIBAOBJS:.o=.S)
-OBJS	:= $(addprefix $(obj),$(COBJS))
-ELF	:= $(addprefix $(obj),$(ELF))
+OBJS	:= $(addprefix $(obj)/,$(COBJS))
+ELF	:= $(addprefix $(obj)/,$(ELF))
 
 gcclibdir := $(shell dirname `$(CC) -print-libgcc-file-name`)
 
@@ -67,13 +67,13 @@ $(LIB):	$(LIBOBJS)
 	$(call cmd_link_o_target, $(LIBOBJS))
 
 $(ELF):
-$(obj)%:	$(obj)%.o $(LIB)
+$(obj)/%:	$(obj)/%.o $(LIB)
 		$(LD) $(LDFLAGS) -g -Ttext $(CONFIG_STANDALONE_LOAD_ADDR) \
 			-o $@ -e $(SYM_PREFIX)$(notdir $(<:.o=)) $< $(LIB) \
 			-L$(gcclibdir) -lgcc
 
-$(obj)%.srec:	$(obj)%
+$(obj)/%.srec:	$(obj)/%
 		$(OBJCOPY) -O srec $< $@ 2>/dev/null
 
-$(obj)%.bin:	$(obj)%
+$(obj)/%.bin:	$(obj)/%
 		$(OBJCOPY) -O binary $< $@ 2>/dev/null