linux/scripts/Makefile.asm-generic
Masahiro Yamada 919987318a kbuild: generate asm-generic wrappers if mandatory headers are missing
Some time ago, Sam pointed out a certain degree of overwrap between
generic-y and mandatory-y. (https://lkml.org/lkml/2017/7/10/121)

I tweaked the meaning of mandatory-y a little bit; now it defines the
minimum set of ASM headers that all architectures must have.

If arch does not have specific implementation of a mandatory header,
Kbuild will let it fallback to the asm-generic one by automatically
generating a wrapper. This will allow to drop lots of redundant
generic-y defines.

Previously, "mandatory" was used in the context of UAPI, but I guess
this can be extended to kernel space ASM headers.

Suggested-by: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Acked-by: Sam Ravnborg <sam@ravnborg.org>
2019-01-06 09:46:51 +09:00

48 lines
1.4 KiB
Makefile

# SPDX-License-Identifier: GPL-2.0
# include/asm-generic contains a lot of files that are used
# verbatim by several architectures.
#
# This Makefile reads the file arch/$(SRCARCH)/include/(uapi/)/asm/Kbuild
# and for each file listed in this file with generic-y creates
# a small wrapper file in arch/$(SRCARCH)/include/generated/(uapi/)/asm.
PHONY := all
all:
src := $(subst /generated,,$(obj))
-include $(src)/Kbuild
include scripts/Kbuild.include
# If arch does not implement mandatory headers, fallback to asm-generic ones.
mandatory-y := $(filter-out $(generated-y), $(mandatory-y))
generic-y += $(foreach f, $(mandatory-y), $(if $(wildcard $(srctree)/$(src)/$(f)),,$(f)))
generic-y := $(addprefix $(obj)/, $(generic-y))
generated-y := $(addprefix $(obj)/, $(generated-y))
# Remove stale wrappers when the corresponding files are removed from generic-y
old-headers := $(wildcard $(obj)/*.h)
unwanted := $(filter-out $(generic-y) $(generated-y),$(old-headers))
quiet_cmd_wrap = WRAP $@
cmd_wrap = echo "\#include <asm-generic/$*.h>" > $@
quiet_cmd_remove = REMOVE $(unwanted)
cmd_remove = rm -f $(unwanted)
all: $(generic-y)
$(if $(unwanted),$(call cmd,remove))
@:
$(obj)/%.h:
$(call cmd,wrap)
# Create output directory. Skip it if at least one old header exists
# since we know the output directory already exists.
ifeq ($(old-headers),)
$(shell mkdir -p $(obj))
endif
.PHONY: $(PHONY)