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>
diff --git a/examples/api/Makefile b/examples/api/Makefile
index ee3c487..db0bb34 100644
--- a/examples/api/Makefile
+++ b/examples/api/Makefile
@@ -40,23 +40,23 @@
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 $@ $<