[PATCH RFC] Kbuild: Makefile: warn if auto.conf is obsolete

From: Mauro Carvalho Chehab
Date: Thu Apr 30 2020 - 15:25:18 EST


A new behavior on more recent kernels require to always call
"make modules_prepare" after *any* Kconfig changes.

This is not what a poor mortal would be expecting on a building
system, as it should, IMHO, be able to detect and auto-run
whatever is needed to use the newer setup.

Yet, while this is not solved, let's at least stop the build
and produce a warning, to notify the user about that.

Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@xxxxxxxxxx>
---

I would still prefer to call "make modules_prepare" directly,
on such cases, but just calling "make -C . modules_prepare" doesn't
work. So, the next best thing would be to at least print a message
and don't try to do a build with a broken auto.conf file.

Makefile | 5 +++++
1 file changed, 5 insertions(+)

diff --git a/Makefile b/Makefile
index 70def4907036..492ee2396ab9 100644
--- a/Makefile
+++ b/Makefile
@@ -1632,6 +1632,11 @@ $(objtree)/Module.symvers:
build-dirs := $(KBUILD_EXTMOD)
PHONY += modules
modules: descend $(objtree)/Module.symvers
+ @if [ $(KCONFIG_CONFIG) -nt include/config/auto.conf ]; then \
+ echo " WARNING: $(KCONFIG_CONFIG) was modified. Need to run:"; \
+ echo " $(MAKE) modules_prepare"; \
+ exit -1; \
+ fi
$(Q)$(MAKE) -f $(srctree)/scripts/Makefile.modpost

PHONY += modules_install
--
2.25.4