We want to change the build system to include config.mk
only from ./Makefile and spl/Makefile.
We must prepare for that in this commit.
$(src) is a moving target and not handy for our purpose.
We must replace it with a fixed path.
Signed-off-by: Masahiro Yamada <yamada.m@jp.panasonic.com>
The syntax
CROSS_COMIPLE ?= <cross_compiler_prefix>
does not work because config.mk is parsed after
exporting CROSS_COMPILE.
Like Linux Kernel's arch/$(ARCH)/Makefile,
we must write as follows:
ifeq ($(CROSS_COMPILE),)
CROSS_COMPILE := <cross_compiler_prefix>
endif
Signed-off-by: Masahiro Yamada <yamada.m@jp.panasonic.com>
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>
