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kbuild: change out-of-tree build

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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>
This commit is contained in:
Masahiro Yamada 2014-02-04 17:24:24 +09:00 • committed by Tom Rini
parent d958002589
commit 9e4140329e
64 changed files with 611 additions and 743 deletions
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16
examples/api/Makefile
View file

@ -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 $@ $<