kbuild: add real-prereqs shorthand for $(filter-out FORCE,$^)

In Kbuild, if_changed and friends must have FORCE as a prerequisite.

Hence, $(filter-out FORCE,$^) or $(filter-out $(PHONY),$^) is a common
idiom to get the names of all the prerequisites except phony targets.

Add real-prereqs as a shorthand.

Note:
We cannot replace $(filter %.o,$^) in cmd_link_multi-m because $^ may
include auto-generated dependencies from the .*.cmd file when a single
object module is changed into a multi object module. Refer to commit
69ea912fda74 ("kbuild: remove unneeded link_multi_deps"). I added some
comment to avoid accidental breakage.

Signed-off-by: Masahiro Yamada <[e-mail]>
Acked-by: Rob Herring <[e-mail]>

Documentation/devicetree/bindings/Makefile

···
 extra-y += $(DT_TMP_SCHEMA)
 
 quiet_cmd_mk_schema = SCHEMA  $@
-      cmd_mk_schema = $(DT_MK_SCHEMA) $(DT_MK_SCHEMA_FLAGS) -o $@ $(filter-out FORCE, $^)
+      cmd_mk_schema = $(DT_MK_SCHEMA) $(DT_MK_SCHEMA_FLAGS) -o $@ $(real-prereqs)
 
 DT_DOCS = $(shell cd $(srctree)/$(src) && find * -name '*.yaml')
 DT_SCHEMA_FILES ?= $(addprefix $(src)/,$(DT_DOCS))

arch/mips/boot/Makefile

···
 targets += vmlinux.its.S
 
 quiet_cmd_its_cat = CAT     $@
-      cmd_its_cat = cat $(filter-out $(PHONY), $^) >$@
+      cmd_its_cat = cat $(real-prereqs) >$@
 
 $(obj)/vmlinux.its.S: $(addprefix $(srctree)/arch/mips/$(PLATFORM)/,$(ITS_INPUTS)) FORCE
 	$(call if_changed,its_cat)

arch/powerpc/boot/Makefile

···
       cmd_bootas = $(BOOTCC) -Wp,-MD,$(depfile) $(BOOTAFLAGS) -c -o $@ $<
 
 quiet_cmd_bootar = BOOTAR  $@
-      cmd_bootar = $(BOOTAR) $(BOOTARFLAGS) $@.$$$$ $(filter-out FORCE,$^); mv $@.$$$$ $@
+      cmd_bootar = $(BOOTAR) $(BOOTARFLAGS) $@.$$$$ $(real-prereqs); mv $@.$$$$ $@
 
 $(obj-libfdt): $(obj)/%.o: $(srctree)/scripts/dtc/libfdt/%.c FORCE
 	$(call if_changed_dep,bootcc)

arch/s390/boot/Makefile

···
 	$(Q)$(MAKE) $(build)=$(obj)/compressed $@
 
 quiet_cmd_ar = AR      $@
-      cmd_ar = rm -f $@; $(AR) rcsTP$(KBUILD_ARFLAGS) $@ $(filter $(OBJECTS), $^)
+      cmd_ar = rm -f $@; $(AR) rcsTP$(KBUILD_ARFLAGS) $@ $(real-prereqs)
 
 $(obj)/startup.a: $(OBJECTS) FORCE
 	$(call if_changed,ar)

arch/x86/realmode/rm/Makefile

···
 sed-pasyms := -n -r -e 's/^([0-9a-fA-F]+) [ABCDGRSTVW] (.+)$$/pa_\2 = \2;/p'
 
 quiet_cmd_pasyms = PASYMS  $@
-      cmd_pasyms = $(NM) $(filter-out FORCE,$^) | \
-		   sed $(sed-pasyms) | sort | uniq > $@
+      cmd_pasyms = $(NM) $(real-prereqs) | sed $(sed-pasyms) | sort | uniq > $@
 
 targets += pasyms.h
 $(obj)/pasyms.h: $(REALMODE_OBJS) FORCE

scripts/Kbuild.include

···
 basetarget = $(basename $(notdir $@))
 
 ###
+# real prerequisites without phony targets
+real-prereqs = $(filter-out $(PHONY), $^)
+
+###
 # Escape single quote for use in echo statements
 escsq = $(subst $(squote),'\$(squote)',$1)
 

scripts/Makefile.build

···
 ifdef builtin-target
 
 quiet_cmd_ar_builtin = AR      $@
-      cmd_ar_builtin = rm -f $@; \
-                     $(AR) rcSTP$(KBUILD_ARFLAGS) $@ $(filter $(real-obj-y), $^)
+      cmd_ar_builtin = rm -f $@; $(AR) rcSTP$(KBUILD_ARFLAGS) $@ $(real-prereqs)
 
 $(builtin-target): $(real-obj-y) FORCE
 	$(call if_changed,ar_builtin)
···
 quiet_cmd_link_l_target = AR      $@
 
 # lib target archives do get a symbol table and index
-cmd_link_l_target = rm -f $@; $(AR) rcsTP$(KBUILD_ARFLAGS) $@ $(lib-y)
+cmd_link_l_target = rm -f $@; $(AR) rcsTP$(KBUILD_ARFLAGS) $@ $(real-prereqs)
 
 $(lib-target): $(lib-y) FORCE
 	$(call if_changed,link_l_target)
···
 
 endif
 
+# NOTE:
+# Do not replace $(filter %.o,^) with $(real-prereqs). When a single object
+# module is turned into a multi object module, $^ will contain header file
+# dependencies recorded in the .*.cmd file.
 quiet_cmd_link_multi-m = LD [M]  $@
 cmd_link_multi-m = $(LD) $(ld_flags) -r -o $@ $(filter %.o,$^) $(cmd_secanalysis)
 

scripts/Makefile.lib

···
 # ---------------------------------------------------------------------------
 
 quiet_cmd_ld = LD      $@
-cmd_ld = $(LD) $(ld_flags) $(filter-out FORCE,$^) -o $@
+      cmd_ld = $(LD) $(ld_flags) $(real-prereqs) -o $@
 
 # Objcopy
 # ---------------------------------------------------------------------------
···
 # ---------------------------------------------------------------------------
 
 quiet_cmd_gzip = GZIP    $@
-      cmd_gzip = cat $(filter-out FORCE,$^) | gzip -n -f -9 > $@
+      cmd_gzip = cat $(real-prereqs) | gzip -n -f -9 > $@
 
 # DTC
 # ---------------------------------------------------------------------------
···
 # append the size as a 32-bit littleendian number as gzip does.
 size_append = printf $(shell						\
 dec_size=0;								\
-for F in $(filter-out FORCE,$^); do					\
+for F in $(real-prereqs); do					\
 	fsize=$$($(CONFIG_SHELL) $(srctree)/scripts/file-size.sh $$F);	\
 	dec_size=$$(expr $$dec_size + $$fsize);				\
 done;									\
···
 )
 
 quiet_cmd_bzip2 = BZIP2   $@
-      cmd_bzip2 = (cat $(filter-out FORCE,$^) | bzip2 -9 && $(size_append)) > $@
+      cmd_bzip2 = (cat $(real-prereqs) | bzip2 -9 && $(size_append)) > $@
 
 # Lzma
 # ---------------------------------------------------------------------------
 
 quiet_cmd_lzma = LZMA    $@
-      cmd_lzma = (cat $(filter-out FORCE,$^) | lzma -9 && $(size_append)) > $@
+      cmd_lzma = (cat $(real-prereqs) | lzma -9 && $(size_append)) > $@
 
 quiet_cmd_lzo = LZO     $@
-      cmd_lzo = (cat $(filter-out FORCE,$^) | lzop -9 && $(size_append)) > $@
+      cmd_lzo = (cat $(real-prereqs) | lzop -9 && $(size_append)) > $@
 
 quiet_cmd_lz4 = LZ4     $@
-      cmd_lz4 = (cat $(filter-out FORCE,$^) | lz4c -l -c1 stdin stdout && \
+      cmd_lz4 = (cat $(real-prereqs) | lz4c -l -c1 stdin stdout && \
                   $(size_append)) > $@
 
 # U-Boot mkimage
···
 # big dictionary would increase the memory usage too much in the multi-call
 # decompression mode. A BCJ filter isn't used either.
 quiet_cmd_xzkern = XZKERN  $@
-cmd_xzkern = (cat $(filter-out FORCE,$^) | \
+      cmd_xzkern = (cat $(real-prereqs) | \
 	sh $(srctree)/scripts/xz_wrap.sh && $(size_append)) > $@
 
 quiet_cmd_xzmisc = XZMISC  $@
-cmd_xzmisc = (cat $(filter-out FORCE,$^) | \
+      cmd_xzmisc = (cat $(real-prereqs) | \
 	xz --check=crc32 --lzma2=dict=1MiB) > $@
 
 # ASM offsets

scripts/Makefile.modpost

···
       cmd_ld_ko_o =                                                     \
 	$(LD) -r $(KBUILD_LDFLAGS)                                      \
                  $(KBUILD_LDFLAGS_MODULE) $(LDFLAGS_MODULE)             \
-                 -o $@ $(filter-out FORCE,$^) ;                         \
+                 -o $@ $(real-prereqs) ;                                \
 	$(if $(ARCH_POSTLINK), $(MAKE) -f $(ARCH_POSTLINK) $@, true)
 
 $(modules): %.ko :%.o %.mod.o FORCE