[PATCH v3 0/4] Don't create Python bytecode when building the kernel

[PATCH v3 0/4] Don't create Python bytecode when building the kernel

[Mauro Carvalho Chehab]

As reported by Andy, the Kernel build system runs kernel-doc script for DRM,
when W=1. Due to Python's normal behavior, its JIT compiler will create
a bytecode and store it under scripts/lib/*/__pycache__.  As one may be using
O= and even having the sources on a read-only mount point, disable its
creation during build time.

This is done by adding PYTHONDONTWRITEBYTECODE=1 on every place
where the script is called within Kbuild and when called via another script.
 
This only solves half of the issue though, as one may be manually running
the script by hand, without asking Python to not store any bytecode.
This should be OK, but afterwards, git status will list the __pycache__ as
not committed. To prevent that, add *.pyc to .gitignore.

This series contain 4 patches:

- patch 1 adjusts a variable that pass extra data to scripts/kerneldoc.py;
- patch 2moves scripts/kernel-doc location to the main makefile
  and exports it, as scripts/Makefile.build will need it;
- patch 3 disables __pycache__ generation and ensure that the entire Kbuild
  will use KERNELDOC var for the location of kernel-doc;
- patch 4 adds *.pyc at the list of object files to be ignored.

---

v3:
- move KERNELDOC to the main Makefile;
- get rid of the badly-named KERNELDOC_CONF var.

v2:
- added a .gitignore file;
- add PYTHONDONTWRITEBYTECODE=1 to the places where kernel-doc
  is called.

Mauro Carvalho Chehab (4):
  docs: Makefile: get rid of KERNELDOC_CONF env variable
  Makefile: move KERNELDOC macro to the main Makefile
  scripts/kernel-doc.py: don't create *.pyc files
  .gitignore: ignore Python compiled bytecode

 .gitignore                    | 1 +
 Documentation/Makefile        | 5 ++---
 Makefile                      | 5 +++++
 drivers/gpu/drm/Makefile      | 2 +-
 drivers/gpu/drm/i915/Makefile | 2 +-
 include/drm/Makefile          | 2 +-
 scripts/Makefile.build        | 2 +-
 scripts/find-unused-docs.sh   | 2 +-
 8 files changed, 13 insertions(+), 8 deletions(-)

-- 
2.49.0

[PATCH v3 1/4] docs: Makefile: get rid of KERNELDOC_CONF env variable

[Mauro Carvalho Chehab]

Despite its name, what's there is a set of Sphinx arguments that
are passed to sphinx/kerneldoc.py:

- kerneldoc_srctree: location of the source tree;
- kerneldoc_bin: external script to excecute kernel-doc

Drop it, and just place the values at the already-existing
ALLSPHINXOPTS variable.

Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
---
 Documentation/Makefile | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/Documentation/Makefile b/Documentation/Makefile
index c022b97c487e..a006c7681412 100644
--- a/Documentation/Makefile
+++ b/Documentation/Makefile
@@ -61,8 +61,8 @@ endif #HAVE_LATEXMK
 PAPEROPT_a4     = -D latex_paper_size=a4
 PAPEROPT_letter = -D latex_paper_size=letter
 KERNELDOC       = $(srctree)/scripts/kernel-doc.py
-KERNELDOC_CONF  = -D kerneldoc_srctree=$(srctree) -D kerneldoc_bin=$(KERNELDOC)
-ALLSPHINXOPTS   =  $(KERNELDOC_CONF) $(PAPEROPT_$(PAPER)) $(SPHINXOPTS)
+ALLSPHINXOPTS   = -D kerneldoc_srctree=$(srctree) -D kerneldoc_bin=$(KERNELDOC)
+ALLSPHINXOPTS   += $(PAPEROPT_$(PAPER)) $(SPHINXOPTS)
 ifneq ($(wildcard $(srctree)/.config),)
 ifeq ($(CONFIG_RUST),y)
 	# Let Sphinx know we will include rustdoc
-- 
2.49.0

[PATCH v3 2/4] Makefile: move KERNELDOC macro to the main Makefile

[Mauro Carvalho Chehab]

As kernel-doc script is used not only on Documentation, but
also on scripts and drivers/drm Makefiles, move it to the
main makefile, as otherwise sub-makefiles may not have it.

Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
---
 Documentation/Makefile | 1 -
 Makefile               | 5 +++++
 2 files changed, 5 insertions(+), 1 deletion(-)

diff --git a/Documentation/Makefile b/Documentation/Makefile
index a006c7681412..8c1f6a3dfc44 100644
--- a/Documentation/Makefile
+++ b/Documentation/Makefile
@@ -60,7 +60,6 @@ endif #HAVE_LATEXMK
 # Internal variables.
 PAPEROPT_a4     = -D latex_paper_size=a4
 PAPEROPT_letter = -D latex_paper_size=letter
-KERNELDOC       = $(srctree)/scripts/kernel-doc.py
 ALLSPHINXOPTS   = -D kerneldoc_srctree=$(srctree) -D kerneldoc_bin=$(KERNELDOC)
 ALLSPHINXOPTS   += $(PAPEROPT_$(PAPER)) $(SPHINXOPTS)
 ifneq ($(wildcard $(srctree)/.config),)
diff --git a/Makefile b/Makefile
index 38689a0c3605..2a05988740a9 100644
--- a/Makefile
+++ b/Makefile
@@ -458,6 +458,11 @@ endif
 HOSTRUSTC = rustc
 HOSTPKG_CONFIG	= pkg-config
 
+# the KERNELDOC macro needs to be exported, as scripts/Makefile.build
+# has a logic to call it
+KERNELDOC       = $(srctree)/scripts/kernel-doc.py
+export KERNELDOC
+
 KBUILD_USERHOSTCFLAGS := -Wall -Wmissing-prototypes -Wstrict-prototypes \
 			 -O2 -fomit-frame-pointer -std=gnu11
 KBUILD_USERCFLAGS  := $(KBUILD_USERHOSTCFLAGS) $(USERCFLAGS)
-- 
2.49.0

[PATCH v3 3/4] scripts/kernel-doc.py: don't create *.pyc files

[Mauro Carvalho Chehab]

As reported by Andy, kernel-doc.py is creating a __pycache__
directory at build time.

Disable creation of __pycache__ for the libraries used by
kernel-doc.py, when excecuted via the build system or via
scripts/find-unused-docs.sh.

Reported-by: Andy Shevchenko <andriy.shevchenko@intel.com>
Closes: https://lore.kernel.org/linux-doc/Z_zYXAJcTD-c3xTe@black.fi.intel.com/
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
---
 drivers/gpu/drm/Makefile      | 2 +-
 drivers/gpu/drm/i915/Makefile | 2 +-
 include/drm/Makefile          | 2 +-
 scripts/Makefile.build        | 2 +-
 scripts/find-unused-docs.sh   | 2 +-
 5 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/Makefile b/drivers/gpu/drm/Makefile
index ed54a546bbe2..d21d0cd2c752 100644
--- a/drivers/gpu/drm/Makefile
+++ b/drivers/gpu/drm/Makefile
@@ -236,7 +236,7 @@ always-$(CONFIG_DRM_HEADER_TEST) += \
 quiet_cmd_hdrtest = HDRTEST $(patsubst %.hdrtest,%.h,$@)
       cmd_hdrtest = \
 		$(CC) $(c_flags) -fsyntax-only -x c /dev/null -include $< -include $<; \
-		$(srctree)/scripts/kernel-doc -none $(if $(CONFIG_WERROR)$(CONFIG_DRM_WERROR),-Werror) $<; \
+		 PYTHONDONTWRITEBYTECODE=1 $(KERNELDOC) -none $(if $(CONFIG_WERROR)$(CONFIG_DRM_WERROR),-Werror) $<; \
 		touch $@
 
 $(obj)/%.hdrtest: $(src)/%.h FORCE
diff --git a/drivers/gpu/drm/i915/Makefile b/drivers/gpu/drm/i915/Makefile
index ed05b131ed3a..ab6b89a163e7 100644
--- a/drivers/gpu/drm/i915/Makefile
+++ b/drivers/gpu/drm/i915/Makefile
@@ -408,7 +408,7 @@ obj-$(CONFIG_DRM_I915_GVT_KVMGT) += kvmgt.o
 #
 # Enable locally for CONFIG_DRM_I915_WERROR=y. See also scripts/Makefile.build
 ifdef CONFIG_DRM_I915_WERROR
-    cmd_checkdoc = $(srctree)/scripts/kernel-doc -none -Werror $<
+    cmd_checkdoc = PYTHONDONTWRITEBYTECODE=1 $(KERNELDOC) -none -Werror $<
 endif
 
 # header test
diff --git a/include/drm/Makefile b/include/drm/Makefile
index a7bd15d2803e..1df6962556ef 100644
--- a/include/drm/Makefile
+++ b/include/drm/Makefile
@@ -11,7 +11,7 @@ always-$(CONFIG_DRM_HEADER_TEST) += \
 quiet_cmd_hdrtest = HDRTEST $(patsubst %.hdrtest,%.h,$@)
       cmd_hdrtest = \
 		$(CC) $(c_flags) -fsyntax-only -x c /dev/null -include $< -include $<; \
-		$(srctree)/scripts/kernel-doc -none $(if $(CONFIG_WERROR)$(CONFIG_DRM_WERROR),-Werror) $<; \
+		PYTHONDONTWRITEBYTECODE=1 $(KERNELDOC) -none $(if $(CONFIG_WERROR)$(CONFIG_DRM_WERROR),-Werror) $<; \
 		touch $@
 
 $(obj)/%.hdrtest: $(src)/%.h FORCE
diff --git a/scripts/Makefile.build b/scripts/Makefile.build
index 13dcd86e74ca..884dc86ce04e 100644
--- a/scripts/Makefile.build
+++ b/scripts/Makefile.build
@@ -83,7 +83,7 @@ else ifeq ($(KBUILD_CHECKSRC),2)
 endif
 
 ifneq ($(KBUILD_EXTRA_WARN),)
-  cmd_checkdoc = $(srctree)/scripts/kernel-doc -none $(KDOCFLAGS) \
+  cmd_checkdoc = PYTHONDONTWRITEBYTECODE=1 $(KERNELDOC) -none $(KDOCFLAGS) \
         $(if $(findstring 2, $(KBUILD_EXTRA_WARN)), -Wall) \
         $<
 endif
diff --git a/scripts/find-unused-docs.sh b/scripts/find-unused-docs.sh
index ee6a50e33aba..d6d397fbf917 100755
--- a/scripts/find-unused-docs.sh
+++ b/scripts/find-unused-docs.sh
@@ -54,7 +54,7 @@ for file in `find $1 -name '*.c'`; do
 	if [[ ${FILES_INCLUDED[$file]+_} ]]; then
 	continue;
 	fi
-	str=$(scripts/kernel-doc -export "$file" 2>/dev/null)
+	str=$(PYTHONDONTWRITEBYTECODE=1 scripts/kernel-doc -export "$file" 2>/dev/null)
 	if [[ -n "$str" ]]; then
 	echo "$file"
 	fi
-- 
2.49.0

[PATCH v3 4/4] .gitignore: ignore Python compiled bytecode

[Mauro Carvalho Chehab]

While the building system doesn't create any Python JIT bytecode,
if one manually runs kernel-doc.py or get_abi.py, Python will,
by default, create a bytecode and store it under scripts/lib/*.

This is normal, and not controlled by the Kernel itself. So,
add *.pyc as an extension to be ignored.

Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
---
 .gitignore | 1 +
 1 file changed, 1 insertion(+)

diff --git a/.gitignore b/.gitignore
index f2f63e47fb88..2e01bc0b2d2a 100644
--- a/.gitignore
+++ b/.gitignore
@@ -39,6 +39,7 @@
 *.mod.c
 *.o
 *.o.*
+*.pyc
 *.patch
 *.rmeta
 *.rpm
-- 
2.49.0

Re: [PATCH v3 4/4] .gitignore: ignore Python compiled bytecode

[Miguel Ojeda]

On Sat, Apr 19, 2025 at 1:50 AM Mauro Carvalho Chehab
<mchehab+huawei@kernel.org> wrote:
>
> +*.pyc
>  *.patch

I think the list is intended to be sorted.

Should `*.pyo` be added as well?

Thanks!

Cheers,
Miguel

Re: [PATCH v3 4/4] .gitignore: ignore Python compiled bytecode

[Miguel Ojeda]

On Sat, Apr 19, 2025 at 11:17 AM Miguel Ojeda
<miguel.ojeda.sandonis@gmail.com> wrote:
>
> Should `*.pyo` be added as well?

I think this one is a no, given even oldoldstable Debian ships new
enough Python.

Cheers,
Miguel

Re: [PATCH v3 4/4] .gitignore: ignore Python compiled bytecode

[Andy Shevchenko]

On Sat, Apr 19, 2025 at 11:17:33AM +0200, Miguel Ojeda wrote:
> On Sat, Apr 19, 2025 at 1:50 AM Mauro Carvalho Chehab
> <mchehab+huawei@kernel.org> wrote:
> >
> > +*.pyc
> >  *.patch
> 
> I think the list is intended to be sorted.

+1, I told already twice, I dunno if my messages were seen.

-- 
With Best Regards,
Andy Shevchenko

Re: [PATCH v3 0/4] Don't create Python bytecode when building the kernel

[Andy Shevchenko]

On Sat, Apr 19, 2025 at 07:50:01AM +0800, Mauro Carvalho Chehab wrote:
> As reported by Andy, the Kernel build system runs kernel-doc script for DRM,
> when W=1. Due to Python's normal behavior, its JIT compiler will create
> a bytecode and store it under scripts/lib/*/__pycache__.  As one may be using
> O= and even having the sources on a read-only mount point, disable its
> creation during build time.
> 
> This is done by adding PYTHONDONTWRITEBYTECODE=1 on every place
> where the script is called within Kbuild and when called via another script.
>  
> This only solves half of the issue though, as one may be manually running
> the script by hand, without asking Python to not store any bytecode.
> This should be OK, but afterwards, git status will list the __pycache__ as
> not committed. To prevent that, add *.pyc to .gitignore.
> 
> This series contain 4 patches:
> 
> - patch 1 adjusts a variable that pass extra data to scripts/kerneldoc.py;
> - patch 2moves scripts/kernel-doc location to the main makefile
>   and exports it, as scripts/Makefile.build will need it;
> - patch 3 disables __pycache__ generation and ensure that the entire Kbuild
>   will use KERNELDOC var for the location of kernel-doc;
> - patch 4 adds *.pyc at the list of object files to be ignored.

This one works for me, thanks!
Tested-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>

-- 
With Best Regards,
Andy Shevchenko