Commit 91998731 authored by Masahiro Yamada's avatar Masahiro Yamada
Browse files

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. (


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: default avatarSam Ravnborg <>
Signed-off-by: default avatarMasahiro Yamada <>
Acked-by: default avatarSam Ravnborg <>
parent d4ce5458
......@@ -1296,9 +1296,12 @@ See subsequent chapter for the syntax of the Kbuild file.
--- 7.4 mandatory-y
mandatory-y is essentially used by include/uapi/asm-generic/Kbuild.asm
to define the minimum set of headers that must be exported in
mandatory-y is essentially used by include/(uapi/)asm-generic/Kbuild.asm
to define the minimum set of ASM headers that all architectures must have.
This works like optional generic-y. If a mandatory header is missing
in arch/$(ARCH)/include/(uapi/)/asm, Kbuild will automatically generate
a wrapper of the asm-generic one.
The convention is to list one subdir per line and
preferably in alphabetic order.
......@@ -14,6 +14,10 @@ src := $(subst /generated,,$(obj))
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))
......@@ -56,13 +56,6 @@ check-file := $(installdir)/.check
all-files := $(header-files) $(genhdr-files)
output-files := $(addprefix $(installdir)/, $(all-files))
ifneq ($(mandatory-y),)
missing := $(filter-out $(all-files),$(mandatory-y))
ifneq ($(missing),)
$(error Some mandatory headers ($(missing)) are missing in $(obj))
# Work out what needs to be removed
oldheaders := $(patsubst $(installdir)/%,%,$(wildcard $(installdir)/*.h))
unwanted := $(filter-out $(all-files),$(oldheaders))
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