kbuild: use $(src) instead of $(srctree)/$(src) for source directory

Kbuild conventionally uses $(obj)/ for generated files, and $(src)/ for
checked-in source files. It is merely a convention without any functional
difference. In fact, $(obj) and $(src) are exactly the same, as defined
in scripts/Makefile.build:

    src := $(obj)

When the kernel is built in a separate output directory, $(src) does
not accurately reflect the source directory location. While Kbuild
resolves this discrepancy by specifying VPATH=$(srctree) to search for
source files, it does not cover all cases. For example, when adding a
header search path for local headers, -I$(srctree)/$(src) is typically
passed to the compiler.

This introduces inconsistency between upstream and downstream Makefiles
because $(src) is used instead of $(srctree)/$(src) for the latter.

To address this inconsistency, this commit changes the semantics of
$(src) so that it always points to the directory in the source tree.

Going forward, the variables used in Makefiles will have the following
meanings:

  $(obj)     - directory in the object tree
  $(src)     - directory in the source tree  (changed by this commit)
  $(objtree) - the top of the kernel object tree
  $(srctree) - the top of the kernel source tree

Consequently, $(srctree)/$(src) in upstream Makefiles need to be replaced
with $(src).

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nicolas Schier <nicolas@fjasle.eu>

1 files changed, 3 insertions, 3 deletions

diff --git a/scripts/Makefile.asm-generic b/scripts/Makefile.asm-generic
index 8d01b37b7677..1486abf34c7c 100644
--- a/scripts/Makefile.asm-generic
+++ b/scripts/Makefile.asm-generic
@@ -9,7 +9,7 @@
 PHONY := all
 all:
 
-src := $(subst /generated,,$(obj))
+src := $(srctree)/$(subst /generated,,$(obj))
 
 include $(srctree)/scripts/Kbuild.include
 -include $(kbuild-file)
@@ -20,14 +20,14 @@ include $(srctree)/$(generic)/Kbuild
 endif
 
 redundant := $(filter $(mandatory-y) $(generated-y), $(generic-y))
-redundant += $(foreach f, $(generic-y), $(if $(wildcard $(srctree)/$(src)/$(f)),$(f)))
+redundant += $(foreach f, $(generic-y), $(if $(wildcard $(src)/$(f)),$(f)))
 redundant := $(sort $(redundant))
 $(if $(redundant),\
 	$(warning redundant generic-y found in $(src)/Kbuild: $(redundant)))
 
 # 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   += $(foreach f, $(mandatory-y), $(if $(wildcard $(src)/$(f)),,$(f)))
 
 generic-y   := $(addprefix $(obj)/, $(generic-y))
 generated-y := $(addprefix $(obj)/, $(generated-y))