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>

7 files changed, 19 insertions, 21 deletions

diff --git a/drivers/gpu/drm/amd/amdgpu/Makefile b/drivers/gpu/drm/amd/amdgpu/Makefile
index 4536c8ad0e11..e568e89283c0 100644
--- a/drivers/gpu/drm/amd/amdgpu/Makefile
+++ b/drivers/gpu/drm/amd/amdgpu/Makefile
@@ -23,7 +23,7 @@
 # Makefile for the drm device driver.  This driver provides support for the
 # Direct Rendering Infrastructure (DRI) in XFree86 4.1.0 and higher.
 
-FULL_AMD_PATH=$(srctree)/$(src)/..
+FULL_AMD_PATH=$(src)/..
 DISPLAY_FOLDER_NAME=display
 FULL_AMD_DISPLAY_PATH = $(FULL_AMD_PATH)/$(DISPLAY_FOLDER_NAME)
 
diff --git a/drivers/gpu/drm/arm/display/komeda/Makefile b/drivers/gpu/drm/arm/display/komeda/Makefile
index 1931a7fa1a14..cf5287fcbbc2 100644
--- a/drivers/gpu/drm/arm/display/komeda/Makefile
+++ b/drivers/gpu/drm/arm/display/komeda/Makefile
@@ -1,8 +1,8 @@
 # SPDX-License-Identifier: GPL-2.0
 
 ccflags-y := \
-	-I $(srctree)/$(src)/../include \
-	-I $(srctree)/$(src)
+	-I $(src)/../include \
+	-I $(src)
 
 komeda-y := \
 	komeda_drv.o \
diff --git a/drivers/gpu/drm/i915/Makefile b/drivers/gpu/drm/i915/Makefile
index fba73c38e235..2220448ed07f 100644
--- a/drivers/gpu/drm/i915/Makefile
+++ b/drivers/gpu/drm/i915/Makefile
@@ -41,7 +41,7 @@ CFLAGS_display/intel_fbdev.o = -Wno-override-init
 # drivers. Define I915 when building i915.
 subdir-ccflags-y += -DI915
 
-subdir-ccflags-y += -I$(srctree)/$(src)
+subdir-ccflags-y += -I$(src)
 
 # Please keep these build lists sorted!
 
@@ -434,7 +434,7 @@ no-header-test := \
 
 always-$(CONFIG_DRM_I915_WERROR) += \
 	$(patsubst %.h,%.hdrtest, $(filter-out $(no-header-test), \
-		$(shell cd $(srctree)/$(src) && find * -name '*.h')))
+		$(shell cd $(src) && find * -name '*.h')))
 
 quiet_cmd_hdrtest = HDRTEST $(patsubst %.hdrtest,%.h,$@)
       cmd_hdrtest = $(CC) $(filter-out $(CFLAGS_GCOV), $(c_flags)) -S -o /dev/null -x c /dev/null -include $<; \
diff --git a/drivers/gpu/drm/imagination/Makefile b/drivers/gpu/drm/imagination/Makefile
index ec6db8e9b403..9bc6a3884c22 100644
--- a/drivers/gpu/drm/imagination/Makefile
+++ b/drivers/gpu/drm/imagination/Makefile
@@ -1,7 +1,7 @@
 # SPDX-License-Identifier: GPL-2.0-only OR MIT
 # Copyright (c) 2023 Imagination Technologies Ltd.
 
-subdir-ccflags-y := -I$(srctree)/$(src)
+subdir-ccflags-y := -I$(src)
 
 powervr-y := \
 	pvr_ccb.o \
diff --git a/drivers/gpu/drm/msm/Makefile b/drivers/gpu/drm/msm/Makefile
index b21ae2880c71..b8cc007fc1b9 100644
--- a/drivers/gpu/drm/msm/Makefile
+++ b/drivers/gpu/drm/msm/Makefile
@@ -1,8 +1,8 @@
 # SPDX-License-Identifier: GPL-2.0
-ccflags-y := -I $(srctree)/$(src)
-ccflags-y += -I $(srctree)/$(src)/disp/dpu1
-ccflags-$(CONFIG_DRM_MSM_DSI) += -I $(srctree)/$(src)/dsi
-ccflags-$(CONFIG_DRM_MSM_DP) += -I $(srctree)/$(src)/dp
+ccflags-y := -I $(src)
+ccflags-y += -I $(src)/disp/dpu1
+ccflags-$(CONFIG_DRM_MSM_DSI) += -I $(src)/dsi
+ccflags-$(CONFIG_DRM_MSM_DP) += -I $(src)/dp
 
 msm-y := \
 	adreno/adreno_device.o \
diff --git a/drivers/gpu/drm/nouveau/Kbuild b/drivers/gpu/drm/nouveau/Kbuild
index cf6b3a80c0c8..c32c01827c1d 100644
--- a/drivers/gpu/drm/nouveau/Kbuild
+++ b/drivers/gpu/drm/nouveau/Kbuild
@@ -1,10 +1,8 @@
-NOUVEAU_PATH ?= $(srctree)
-
 # SPDX-License-Identifier: MIT
-ccflags-y += -I $(NOUVEAU_PATH)/$(src)/include
-ccflags-y += -I $(NOUVEAU_PATH)/$(src)/include/nvkm
-ccflags-y += -I $(NOUVEAU_PATH)/$(src)/nvkm
-ccflags-y += -I $(NOUVEAU_PATH)/$(src)
+ccflags-y += -I $(src)/include
+ccflags-y += -I $(src)/include/nvkm
+ccflags-y += -I $(src)/nvkm
+ccflags-y += -I $(src)
 
 # NVKM - HW resource manager
 #- code also used by various userspace tools/tests
diff --git a/drivers/gpu/drm/xe/Makefile b/drivers/gpu/drm/xe/Makefile
index c29a850859ad..8162a522222b 100644
--- a/drivers/gpu/drm/xe/Makefile
+++ b/drivers/gpu/drm/xe/Makefile
@@ -32,7 +32,7 @@ endif
 # Enable -Werror in CI and development
 subdir-ccflags-$(CONFIG_DRM_XE_WERROR) += -Werror
 
-subdir-ccflags-y += -I$(obj) -I$(srctree)/$(src)
+subdir-ccflags-y += -I$(obj) -I$(src)
 
 # generated sources
 hostprogs := xe_gen_wa_oob
@@ -43,7 +43,7 @@ quiet_cmd_wa_oob = GEN     $(notdir $(generated_oob))
       cmd_wa_oob = mkdir -p $(@D); $^ $(generated_oob)
 
 $(obj)/generated/%_wa_oob.c $(obj)/generated/%_wa_oob.h: $(obj)/xe_gen_wa_oob \
-		 $(srctree)/$(src)/xe_wa_oob.rules
+		 $(src)/xe_wa_oob.rules
 	$(call cmd,wa_oob)
 
 uses_generated_oob := \
@@ -166,8 +166,8 @@ endif
 
 # i915 Display compat #defines and #includes
 subdir-ccflags-$(CONFIG_DRM_XE_DISPLAY) += \
-	-I$(srctree)/$(src)/display/ext \
-	-I$(srctree)/$(src)/compat-i915-headers \
+	-I$(src)/display/ext \
+	-I$(src)/compat-i915-headers \
 	-I$(srctree)/drivers/gpu/drm/i915/display/ \
 	-Ddrm_i915_gem_object=xe_bo \
 	-Ddrm_i915_private=xe_device
@@ -310,7 +310,7 @@ ifneq ($(CONFIG_DRM_XE_DISPLAY),y)
 endif
 
 always-$(CONFIG_DRM_XE_WERROR) += \
-	$(patsubst %.h,%.hdrtest, $(shell cd $(srctree)/$(src) && find * -name '*.h' $(hdrtest_find_args)))
+	$(patsubst %.h,%.hdrtest, $(shell cd $(src) && find * -name '*.h' $(hdrtest_find_args)))
 
 quiet_cmd_hdrtest = HDRTEST $(patsubst %.hdrtest,%.h,$@)
       cmd_hdrtest = $(CC) -DHDRTEST $(filter-out $(CFLAGS_GCOV), $(c_flags)) -S -o /dev/null -x c /dev/null -include $<; touch $@