kbuild: refactor fdtoverlay rule

Rename overlay-y to multi-dtb-y, which is a consistent name with
multi-obj-y. Also, use multi-search to avoid code duplication.

Introduce real-dtb-y, which is a consistent name with real-obj-y,
to contain primitive blobs compiled from *.dts. This is used to
calculate the list of *.dt.yaml files.

Set -@ to base DTB without using $(eval ).
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

scripts/Makefile.build

@@ -354,7 +354,7 @@ $(obj)/%.o: $(src)/%.S $(objtool_dep) FORCE
 
 targets += $(filter-out $(subdir-builtin), $(real-obj-y))
 targets += $(filter-out $(subdir-modorder), $(real-obj-m))
-targets += $(lib-y) $(always-y) $(MAKECMDGOALS)
+targets += $(real-dtb-y) $(lib-y) $(always-y) $(MAKECMDGOALS)
 
 # Linker scripts preprocessor (.lds.S -> .lds)
 # ---------------------------------------------------------------------------

scripts/Makefile.lib

@@ -78,24 +78,18 @@ always-y += $(userprogs-always-y) $(userprogs-always-m)
 # If CONFIG_OF_ALL_DTBS is enabled, all DT blobs are built
 dtb-$(CONFIG_OF_ALL_DTBS)       += $(dtb-)
 
-# List all dtbs to be generated by fdtoverlay
-overlay-y := $(foreach m,$(dtb-y), $(if $(strip $($(m:.dtb=-dtbs))),$(m),))
-
-# Generate symbols for the base files so overlays can be applied to them.
-$(foreach m,$(overlay-y), $(eval DTC_FLAGS_$(basename $(firstword $($(m:.dtb=-dtbs)))) += -@))
-
-# Add base dtb and overlay dtbo
-dtb-y += $(foreach m,$(overlay-y), $($(m:.dtb=-dtbs)))
+# Composite DTB (i.e. DTB constructed by overlay)
+multi-dtb-y := $(call multi-search, $(dtb-y), .dtb, -dtbs)
+# Primitive DTB compiled from *.dts
+real-dtb-y := $(call real-search, $(dtb-y), .dtb, -dtbs)
+# Base DTB that overlay is applied onto (each first word of $(*-dtbs) expansion)
+base-dtb-y := $(foreach m, $(multi-dtb-y), $(firstword $(call suffix-search, $m, .dtb, -dtbs)))
 
 always-y			+= $(dtb-y)
 
 ifneq ($(CHECK_DTBS),)
-# Don't run schema checks for dtbs created by fdtoverlay as they don't
-# have corresponding dts files.
-dt-yaml-y := $(filter-out $(overlay-y),$(dtb-y))
-
-always-y += $(patsubst %.dtb,%.dt.yaml, $(dt-yaml-y))
-always-y += $(patsubst %.dtbo,%.dt.yaml, $(dt-yaml-y))
+always-y += $(patsubst %.dtb,%.dt.yaml, $(real-dtb-y))
+always-y += $(patsubst %.dtbo,%.dt.yaml, $(real-dtb-y))
 endif
 
 # Add subdir path
@@ -108,6 +102,8 @@ lib-y		:= $(addprefix $(obj)/,$(lib-y))
 real-obj-y	:= $(addprefix $(obj)/,$(real-obj-y))
 real-obj-m	:= $(addprefix $(obj)/,$(real-obj-m))
 multi-obj-m	:= $(addprefix $(obj)/, $(multi-obj-m))
+multi-dtb-y	:= $(addprefix $(obj)/, $(multi-dtb-y))
+real-dtb-y	:= $(addprefix $(obj)/, $(real-dtb-y))
 subdir-ym	:= $(addprefix $(obj)/,$(subdir-ym))
 
 # Finds the multi-part object the current object will be linked into.
@@ -325,6 +321,9 @@ endif
 
 DTC_FLAGS += $(DTC_FLAGS_$(basetarget))
 
+# Set -@ if the target is a base DTB that overlay is applied onto
+DTC_FLAGS += $(if $(filter $(patsubst $(obj)/%,%,$@), $(base-dtb-y)), -@)
+
 # Generate an assembly file to wrap the output of the device tree compiler
 quiet_cmd_dt_S_dtb= DTB     $@
 cmd_dt_S_dtb=						\
@@ -356,14 +355,12 @@ $(obj)/%.dtb: $(src)/%.dts $(DTC) FORCE
 $(obj)/%.dtbo: $(src)/%.dts $(DTC) FORCE
 	$(call if_changed_dep,dtc)
 
-overlay-y := $(addprefix $(obj)/, $(overlay-y))
-
 quiet_cmd_fdtoverlay = DTOVL   $@
       cmd_fdtoverlay = $(objtree)/scripts/dtc/fdtoverlay -o $@ -i $(real-prereqs)
 
-$(overlay-y): FORCE
+$(multi-dtb-y): FORCE
 	$(call if_changed,fdtoverlay)
-$(call multi_depend, $(overlay-y), .dtb, -dtbs)
+$(call multi_depend, $(multi-dtb-y), .dtb, -dtbs)
 
 DT_CHECKER ?= dt-validate
 DT_CHECKER_FLAGS ?= $(if $(DT_SCHEMA_FILES),,-m)