[PATCH] kbuild: support external module out-of-tree build

[袁建鹏 <yuanjianpeng@xiaomi.com>]

From 205af45582ad0cb1293839a95ee01d383f1cfbf1 Mon Sep 17 00:00:00 2001
From: Yuan Jianpeng <yuanjianpeng@xiaomi.com>
Date: Sat, 25 Mar 2023 10:24:38 +0800
Subject: [PATCH] kbuild: support external module out-of-tree build

A new module build variable KBUILD_EXTMOD_SRC is added which
specifying the external module source path.

Build like this:
make -C $KDIR M=<output dir> KBUILD_EXTMOD_SRC=<module source dir>

Signed-off-by: Yuan Jianpeng <yuanjianpeng@xiaomi.com>
---
 scripts/Makefile.build   | 2 +-
 scripts/Makefile.clean   | 2 +-
 scripts/Makefile.modpost | 2 +-
 3 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/scripts/Makefile.build b/scripts/Makefile.build
index 76323201232a..971a2161d502 100644
--- a/scripts/Makefile.build
+++ b/scripts/Makefile.build
@@ -3,7 +3,7 @@
 # Building
 # ==========================================================================

-src := $(obj)
+src := $(if $(KBUILD_EXTMOD_SRC),$(KBUILD_EXTMOD_SRC)$(patsubst $(KBUILD_EXTMOD)%,%,$(obj)),$(obj))

 PHONY := $(obj)/
 $(obj)/:
diff --git a/scripts/Makefile.clean b/scripts/Makefile.clean
index 3649900696dd..5232a0b6e139 100644
--- a/scripts/Makefile.clean
+++ b/scripts/Makefile.clean
@@ -3,7 +3,7 @@
 # Cleaning up
 # ==========================================================================

-src := $(obj)
+src := $(if $(KBUILD_EXTMOD_SRC),$(KBUILD_EXTMOD_SRC)$(patsubst $(KBUILD_EXTMOD)%,%,$(obj)),$(obj))

 PHONY := __clean
 __clean:
diff --git a/scripts/Makefile.modpost b/scripts/Makefile.modpost
index 0980c58d8afc..3f0b23157c68 100644
--- a/scripts/Makefile.modpost
+++ b/scripts/Makefile.modpost
@@ -103,7 +103,7 @@ else

 # set src + obj - they may be used in the modules's Makefile
 obj := $(KBUILD_EXTMOD)
-src := $(obj)
+src := $(if $(KBUILD_EXTMOD_SRC),$(KBUILD_EXTMOD_SRC)$(patsubst $(KBUILD_EXTMOD)%,%,$(obj)),$(obj))

 # Include the module's Makefile to find KBUILD_EXTRA_SYMBOLS
 include $(kbuild-file)
--
2.38.1

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