[PATCH] kbuild: Run kernel-doc only for in-tree builds

[Nicolas Schier <nsc@kernel.org>]

Stop running kernel-doc when building out-of-tree kernel modules.

Rong Zhang reported that building external modules with W set fails
since v6.19-rc1 as the kernel-doc Python modules are no more available
when building against a kernel module build tree exported by
scripts/package/install-extmod-build.

As there is no good reason for checking documentation when building
out-of-tree kernel modules, stop it.

Fixes: 778b8ebe5192 ("docs: Move the python libraries to tools/lib/python")
Reported-by: Rong Zhang <i@rong.moe>
Closes: https://lore.kernel.org/linux-kbuild/20260129175321.415295-1-i@rong.moe
Suggested-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Reviewed-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Tested-by: Nicolas Schier <nsc@kernel.org>
Signed-off-by: Nicolas Schier <nsc@kernel.org>
---
I left out a 'Cc: stable@kernel.org' as the problem exists just since
v6.19-rc1; please intervene ASAP if you think it should be added.
---

---
Thanks for the report (Rong) and the patch suggestion (Mauro)!
I left out a 'Cc: stable@kernel.org' as the problem exists just since
6.19-rc1; please intervene ASAP if you think it should be added.
---
 scripts/Makefile.build | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/scripts/Makefile.build b/scripts/Makefile.build
index 5037f4715d7491761b75d086441367c6c08c099e..05674bae3c637b4476a11b5e6af630d8daa3b613 100644
--- a/scripts/Makefile.build
+++ b/scripts/Makefile.build
@@ -166,10 +166,12 @@ else ifeq ($(KBUILD_CHECKSRC),2)
         cmd_force_checksrc = $(CHECK) $(CHECKFLAGS) $(c_flags) $<
 endif
 
-ifneq ($(KBUILD_EXTRA_WARN),)
-  cmd_checkdoc = PYTHONDONTWRITEBYTECODE=1 $(PYTHON3) $(KERNELDOC) -none $(KDOCFLAGS) \
-        $(if $(findstring 2, $(KBUILD_EXTRA_WARN)), -Wall) \
-        $<
+ifeq ($(KBUILD_EXTMOD),)
+    ifneq ($(KBUILD_EXTRA_WARN),)
+      cmd_checkdoc = PYTHONDONTWRITEBYTECODE=1 $(PYTHON3) $(KERNELDOC) -none $(KDOCFLAGS) \
+            $(if $(findstring 2, $(KBUILD_EXTRA_WARN)), -Wall) \
+            $<
+    endif
 endif
 
 # Compile C sources (.c)

---
base-commit: 6d60354ea2f90352b22039ed8371c4f4321df90e
change-id: 20260131-run-kernel-doc-only-in-tree-18be87e88208

Best regards,
-- 
Nicolas