linux-kernel - Re: [PATCH] kbuild: install-extmod-build: Add missing python libraries

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Message-ID: <20260130092816.162a48fe@foz.lan>
Date: Fri, 30 Jan 2026 09:32:03 +0100
From: Mauro Carvalho Chehab <mchehab+huawei@...nel.org>
To: Nathan Chancellor <nathan@...nel.org>
Cc: Rong Zhang <i@...g.moe>, Jonathan Corbet <corbet@....net>, Mauro
 Carvalho Chehab <mchehab@...nel.org>, Nicolas Schier <nsc@...nel.org>,
 Masahiro Yamada <masahiroy@...nel.org>, linux-kbuild@...r.kernel.org,
 linux-kernel@...r.kernel.org, linux-doc@...r.kernel.org
Subject: Re: [PATCH] kbuild: install-extmod-build: Add missing python
 libraries

On Thu, 29 Jan 2026 23:40:11 -0700
Nathan Chancellor <nathan@...nel.org> wrote:

> On Fri, Jan 30, 2026 at 06:30:56AM +0100, Mauro Carvalho Chehab wrote:
> > On Thu, 29 Jan 2026 18:11:06 -0700
> > Nathan Chancellor <nathan@...nel.org> wrote:  
> > > On Fri, Jan 30, 2026 at 01:49:55AM +0800, Rong Zhang wrote:  
> ...
> > > >   $ make -C /lib/modules/6.19.0-rc6/build/ M="$(pwd)" modules V=1 W=1
> > > >   [...]
> > > >   make -f /usr/src/linux-headers-6.19.0-rc6/scripts/Makefile.build obj=. need-builtin=1 need-modorder=1
> > > >   # CC [M]  mod.o
> > > >   [...]
> > > >   # cmd_checkdoc mod.o
> > > >   PYTHONDONTWRITEBYTECODE=1 python3 /usr/src/linux-headers-6.19.0-rc6/scripts/kernel-doc.py -none mod.c  
> > 
> > This sounds really weird, as it is trying to run scripts/kernel-doc.py
> > instead of tools/docs/kernel-doc. Does the out-of-tree Makefile
> > override KERNELDOC variable? The current version contains:
> > 	
> > 	KERNELDOC       = $(srctree)/tools/docs/kernel-doc
> > 
> > But somehow it is using the old version before the renames:
> > 
> > 	KERNELDOC       = $(srctree)/scripts/kernel-doc.py  
> 
> Well I think based on the "6.19.0-rc6" in the path above, this is
> mainline, not -next, so the rename has has not happend there yet.

Ah, ok. On your e-mail you mentioned the renaming patch, so I
ended assuming that was the case.

> 
> > Btw, I did a very quick test here, using an old OOT project I have
> > at github:
> > 
> > 	https://github.com/mchehab/xr_serial  
> ...
> > It sounds to me that Rong may be using a Makefile on his OOT project
> > that was not updated to pick the right kernel-doc tool.  
> 
> If I use that project with Rong's original command, the
> linux-upstream-headers package from the pacman-pkg target (which uses
> install-extmod-build), and the following fix up for a more modern kernel
> version, I see the following error:
> 
>   $ make -C /usr/lib/modules/6.19.0-rc7-next-20260129/build M=/tmp/xr_serial modules V=1 W=1
>   ...
>   # CC [M]  xr_serial.o
>     gcc ...
>   # cmd_checkdoc xr_serial.o
>     PYTHONDONTWRITEBYTECODE=1 python3 /usr/lib/modules/6.19.0-rc7-next-20260129/build/tools/docs/kernel-doc -none   xr_serial.c
>   python3: can't open file '/usr/lib/modules/6.19.0-rc7-next-20260129/build/tools/docs/kernel-doc': [Errno 2] No such file or directory
>   make[3]: *** [/usr/lib/modules/6.19.0-rc7-next-20260129/build/scripts/Makefile.build:287: xr_serial.o] Error 2
> 
> If it is not expected that kernel-doc runs for external modules, then
> maybe cmd_checkdoc should also be wrapped in a check for KBUILD_EXTMOD?

I don't particularly see any reason why running kernel-doc for external
modules, as the goal of running it there (outside make htmldocs) is to
detect early problems at linux-next and other CIs.

On the other hand, I also don't see any problem on encapsulating
kernel-doc at the tarball created by install-extmod-build with something
like:

	ifeq ($(KBUILD_EXTMOD),)
		ifneq ($(KBUILD_EXTRA_WARN),)
		  cmd_checkdoc = PYTHONDONTWRITEBYTECODE=1 $(PYTHON3) $(KERNELDOC) -none $(KDOCFLAGS) \
	        	$(if $(findstring 2, $(KBUILD_EXTRA_WARN)), -Wall) \
		        $<
		endif
	endif

at scripts/Makefile.build.


So, feel free to add to either one of the approaches:

Reviewed-by: Mauro Carvalho Chehab <mchehab+huawei@...nel.org>

That's said, it should be noticed that the DRM subsystem also has
some similar code:

	drivers/gpu/drm/Makefile:                PYTHONDONTWRITEBYTECODE=1 $(PYTHON3) $(KERNELDOC) -none $(if $(CONFIG_WERROR)$(CONFIG_DRM_WERROR),-Werror) $<; \
	drivers/gpu/drm/i915/Makefile:    cmd_checkdoc = PYTHONDONTWRITEBYTECODE=1 $(PYTHON3) $(KERNELDOC) -none -Werror $<
	drivers/gpu/drm/i915/Makefile:          $(KERNELDOC) -none -Werror $<; touch $@
	include/drm/Makefile:           PYTHONDONTWRITEBYTECODE=1 $(PYTHON3) $(KERNELDOC) -none $(if $(CONFIG_WERROR)$(CONFIG_DRM_WERROR),-Werror) $<; \
	scripts/Makefile.build:  cmd_checkdoc = PYTHONDONTWRITEBYTECODE=1 $(PYTHON3) $(KERNELDOC) -none $(KDOCFLAGS) \

but I suspect that only scripts/Makefile.build probably need
such check.

Regards,
Mauro