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>

1 files changed, 10 insertions, 9 deletions

diff --git a/rules.mk b/rules.mk
index b36de4d..e4fd337 100644
--- a/rules.mk
+++ b/rules.mk
@@ -6,41 +6,42 @@
 #
 #########################################################################
 
-_depend:	$(obj).depend
+_depend:	$(obj)/.depend
 
 # Split the source files into two camps: those in the current directory, and
 # those somewhere else. For the first camp we want to support CPPFLAGS_<fname>
 # and for the second we don't / can't.
-PWD_SRCS := $(filter $(notdir $(SRCS)),$(SRCS))
-OTHER_SRCS := $(filter-out $(notdir $(SRCS)),$(SRCS))
+PWD_SRCS := $(foreach f,$(SRCS), $(if \
+	$(filter $(if $(KBUILD_SRC),$(srctree)/)$(src)/$(notdir $f),$f), $f))
+OTHER_SRCS := $(filter-out $(PWD_SRCS),$(SRCS))
 
 # This is a list of dependency files to generate
-DEPS := $(basename $(patsubst %,$(obj).depend.%,$(PWD_SRCS)))
+DEPS := $(basename $(addprefix $(obj)/.depend., $(notdir $(PWD_SRCS))))
 
 # Join all the dependencies into a single file, in three parts
 #	1 .Concatenate all the generated depend files together
 #	2. Add in the deps from OTHER_SRCS which we couldn't process
 #	3. Add in the HOSTSRCS
-$(obj).depend:	$(src)Makefile $(TOPDIR)/config.mk $(DEPS) $(OTHER_SRCS) \
+$(obj)/.depend:	$(TOPDIR)/config.mk $(DEPS) $(OTHER_SRCS) \
 		$(HOSTSRCS)
 	cat /dev/null $(DEPS) >$@
 	@for f in $(OTHER_SRCS); do \
 		g=`basename $$f | sed -e 's/\(.*\)\.[[:alnum:]_]/\1.o/'`; \
-		$(CC) -M $(CPPFLAGS) -MQ $(obj)$$g $$f >> $@ ; \
+		$(CC) -M $(CPPFLAGS) -MQ $(obj)/$$g $$f >> $@ ; \
 	done
 	@for f in $(HOSTSRCS); do \
 		g=`basename $$f | sed -e 's/\(.*\)\.[[:alnum:]_]/\1.o/'`; \
-		$(HOSTCC) -M $(HOSTCPPFLAGS) -MQ $(obj)$$g $$f >> $@ ; \
+		$(HOSTCC) -M $(HOSTCPPFLAGS) -MQ $(obj)/$$g $$f >> $@ ; \
 	done
 
 MAKE_DEPEND = $(CC) -M $(CPPFLAGS) $(EXTRA_CPPFLAGS_DEP) \
 		-MQ $(addsuffix .o,$(obj)$(basename $<)) $< >$@
 
 
-$(obj).depend.%:	%.c
+$(obj)/.depend.%:	$(src)/%.c
 	$(MAKE_DEPEND)
 
-$(obj).depend.%:	%.S
+$(obj)/.depend.%:	$(src)/%.S
 	$(MAKE_DEPEND)
 
 #########################################################################