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>

3 files changed, 47 insertions, 32 deletions

diff --git a/scripts/Kbuild.include b/scripts/Kbuild.include
index ca5fd56..6113c13 100644
--- a/scripts/Kbuild.include
+++ b/scripts/Kbuild.include
@@ -165,9 +165,7 @@ ar-option = $(call try-run, $(AR) rc$(1) "$$TMP",$(1),$(2))
 # Shorthand for $(Q)$(MAKE) -f scripts/Makefile.build obj=
 # Usage:
 # $(Q)$(MAKE) $(build)=dir
-#build := -f $(if $(KBUILD_SRC),$(srctree)/)scripts/Makefile.build obj
-# temporary
-build := -f $(srctree)/scripts/Makefile.build -C
+build := -f $(if $(KBUILD_SRC),$(srctree)/)scripts/Makefile.build obj
 
 ###
 # Shorthand for $(Q)$(MAKE) -f scripts/Makefile.modbuiltin obj=
diff --git a/scripts/Makefile.build b/scripts/Makefile.build
index 7789efa..52a44ff 100644
--- a/scripts/Makefile.build
+++ b/scripts/Makefile.build
@@ -2,17 +2,28 @@
 .PHONY: all
 all:
 
+ifeq ($(CONFIG_TPL_BUILD),y)
+  src := $(patsubst tpl/%,%,$(obj))
+else
+  ifeq ($(CONFIG_SPL_BUILD),y)
+    src := $(patsubst spl/%,%,$(obj))
+  else
+    src := $(obj)
+  endif
+endif
+
 include $(srctree)/scripts/Kbuild.include
-include $(TOPDIR)/config.mk
+include $(srctree)/config.mk
 
 # variable LIB is used in examples/standalone/Makefile
-__LIB := $(obj)built-in.o
-LIBGCC = $(obj)libgcc.o
+__LIB := $(obj)/built-in.o
+LIBGCC = $(obj)/libgcc.o
 SRCS :=
 subdir-y :=
 obj-dirs :=
 
-include Makefile
+kbuild-dir := $(if $(filter /%,$(src)),$(src),$(srctree)/$(src))
+include $(kbuild-dir)/Makefile
 
 # Do not include host rules unless needed
 ifneq ($(hostprogs-y)$(hostprogs-m),)
@@ -28,31 +39,37 @@ lib-y := $(sort $(lib-y))
 subdir-y 	+= $(patsubst %/,%,$(filter %/, $(obj-y)))
 obj-y		:= $(patsubst %/, %/built-in.o, $(obj-y))
 subdir-obj-y	:= $(filter %/built-in.o, $(obj-y))
-subdir-obj-y	:= $(addprefix $(obj),$(subdir-obj-y))
+subdir-obj-y	:= $(addprefix $(obj)/,$(subdir-obj-y))
+
+SRCS	+= $(obj-y:.o=.c) $(obj-y:.o=.S) $(lib-y:.o=.c) \
+	$(lib-y:.o=.S) $(extra-y:.o=.c) $(extra-y:.o=.S)
 
-SRCS	+= $(wildcard $(obj-y:.o=.c) $(obj-y:.o=.S) $(lib-y:.o=.c) \
-	$(lib-y:.o=.S) $(extra-y:.o=.c) $(extra-y:.o=.S))
-OBJS	:= $(addprefix $(obj),$(obj-y))
+SRCS := $(addprefix $(if $(KBUILD_SRC),$(srctree)/$(src)/,$(src)/),$(SRCS))
+SRCS := $(wildcard $(SRCS))
+
+OBJS	:= $(addprefix $(obj)/,$(obj-y))
 
 # $(obj-dirs) is a list of directories that contain object files
 
 obj-dirs += $(dir $(OBJS))
 
+_dummy := $(shell [ -d $(obj) ] || mkdir -p $(obj))
+
 # Create directories for object files if directory does not exist
 # Needed when obj-y := dir/file.o syntax is used
 _dummy := $(foreach d,$(obj-dirs), $(shell [ -d $(d) ] || mkdir -p $(d)))
 
-LGOBJS := $(addprefix $(obj),$(sort $(lib-y)))
+LGOBJS := $(addprefix $(obj)/,$(sort $(lib-y)))
 
-all: $(__LIB) $(addprefix $(obj),$(extra-y) $(always)) $(subdir-y)
+all: $(__LIB) $(addprefix $(obj)/,$(extra-y) $(always)) $(subdir-y)
 
-$(__LIB):	$(obj).depend $(OBJS)
+$(__LIB):	$(obj)/.depend $(OBJS)
 	$(call cmd_link_o_target, $(OBJS))
 
 ifneq ($(strip $(lib-y)),)
 all: $(LIBGCC)
 
-$(LIBGCC): $(obj).depend $(LGOBJS)
+$(LIBGCC): $(obj)/.depend $(LGOBJS)
 	$(call cmd_link_o_target, $(LGOBJS))
 endif
 
@@ -63,7 +80,7 @@ endif
 
 ifneq ($(subdir-y),)
 $(subdir-y): FORCE
-	$(MAKE) -C $@ -f $(TOPDIR)/scripts/Makefile.build
+	$(MAKE) $(build)=$(obj)/$@
 endif
 
 #########################################################################
@@ -78,18 +95,18 @@ ALL_CFLAGS += $(EXTRA_CPPFLAGS)
 # See rules.mk
 EXTRA_CPPFLAGS_DEP = $(CPPFLAGS_$(BCURDIR)/$(addsuffix .o,$(basename $<))) \
 		$(CPPFLAGS_$(BCURDIR))
-$(obj)%.s:	%.S
+$(obj)/%.s:	$(src)/%.S
 	$(CPP) $(ALL_AFLAGS) -o $@ $<
-$(obj)%.o:	%.S
+$(obj)/%.o:	$(src)/%.S
 	$(CC)  $(ALL_AFLAGS) -o $@ $< -c
-$(obj)%.o:	%.c
+$(obj)/%.o:	$(src)/%.c
 ifneq ($(CHECKSRC),0)
 	$(CHECK) $(CHECKFLAGS) $(ALL_CFLAGS) $<
 endif
 	$(CC)  $(ALL_CFLAGS) -o $@ $< -c
-$(obj)%.i:	%.c
+$(obj)/%.i:	$(src)/%.c
 	$(CPP) $(ALL_CFLAGS) -o $@ $< -c
-$(obj)%.s:	%.c
+$(obj)/%.s:	$(src)/%.c
 	$(CC)  $(ALL_CFLAGS) -o $@ $< -c -S
 
 # If the list of objects to link is empty, just create an empty built-in.o
@@ -99,11 +116,11 @@ cmd_link_o_target = $(if $(strip $1),\
 
 #########################################################################
 
-# defines $(obj).depend target
+# defines $(obj)/.depend target
 
 include $(TOPDIR)/rules.mk
 
-sinclude $(obj).depend
+sinclude $(obj)/.depend
 
 #########################################################################
 
diff --git a/scripts/Makefile.host.tmp b/scripts/Makefile.host.tmp
index 4b57846..53fe930 100644
--- a/scripts/Makefile.host.tmp
+++ b/scripts/Makefile.host.tmp
@@ -21,11 +21,11 @@ host-objdirs += $(foreach f,$(host-cmulti),                  \
 
 host-objdirs := $(strip $(sort $(filter-out ./,$(host-objdirs))))
 
-__hostprogs     := $(addprefix $(obj),$(__hostprogs))
-host-csingle	:= $(addprefix $(obj),$(host-csingle))
-host-cmulti	:= $(addprefix $(obj),$(host-cmulti))
-host-cobjs	:= $(addprefix $(obj),$(host-cobjs))
-host-objdirs    := $(addprefix $(obj),$(host-objdirs))
+__hostprogs     := $(addprefix $(obj)/,$(__hostprogs))
+host-csingle	:= $(addprefix $(obj)/,$(host-csingle))
+host-cmulti	:= $(addprefix $(obj)/,$(host-cmulti))
+host-cobjs	:= $(addprefix $(obj)/,$(host-cobjs))
+host-objdirs    := $(addprefix $(obj)/,$(host-objdirs))
 
 obj-dirs += $(host-objdirs)
 
@@ -49,13 +49,13 @@ hostc_flags    = $(__hostc_flags)
 #####
 # Compile programs on the host
 
-$(host-csingle): $(obj)%: %.c
+$(host-csingle): $(obj)/%: $(src)/%.c
 	$(HOSTCC) $(HOSTCFLAGS) $(HOST_EXTRACFLAGS) $(HOSTLDFLAGS) $(HOSTCFLAGS_$(@F)) $(HOSTCFLAGS_$(BCURDIR)) -o $@ $<
 
-$(host-cmulti): $(obj)%: $(host-cobjs)
-	$(HOSTCC) $(HOSTLDFLAGS) -o $@ $(addprefix $(obj),$($(@F)-objs)) $(HOSTLOADLIBES_$(@F))
+$(host-cmulti): $(obj)/%: $(host-cobjs)
+	$(HOSTCC) $(HOSTLDFLAGS) -o $@ $(addprefix $(obj)/,$($(@F)-objs)) $(HOSTLOADLIBES_$(@F))
 
-$(host-cobjs): $(obj)%.o: %.c
+$(host-cobjs): $(obj)/%.o: $(src)/%.c
 	$(HOSTCC) $(HOSTCFLAGS) $(HOST_EXTRACFLAGS) $(HOSTCFLAGS_$(@F)) $(HOSTCFLAGS_$(BCURDIR)) -o $@ $< -c
 
 targets += $(host-csingle)  $(host-cmulti) $(host-cobjs)