[PATCH v2 0/2] Better handle and document Python needs for Kernel build

[PATCH v2 0/2] Better handle and document Python needs for Kernel build

[Mauro Carvalho Chehab]

Hi Jon,

It follows the second version of this small series. It contains
missing patches from the python backward-compatibility series.

I dropped support for 2.7 and did some changes at changes.rst
per Akira's request.

They're not urgent, IMO it should be OK to have them merged for 6.17.

The first patch ensures that kernel-doc won't crash with version
3.2 (tested on 3.4, as 3.2 is like an unicorn: docker containers v1
don't run anymore on Fedora, building is broken since at least
Fedora 32, Anaconda doesn't have it anymore).

With this change, on elder versions, it would emit a warning and
do nothing, as the actual code depends on features at 3.6 (f-strings)
and 3.7 (ordered dict).

The second patch changes process/changes.rst. Currently, it makes
one  think that Python is optional. While not having python may
work on some cases, it breaks on arm/arm64 with defconfigs.
It also breaks with allyesconfig/almodconfig (at least on x86/x86_64),
with clang (on some archs) and apparently on some other
subsystems that I didn't care enough to identify, as for me,
breaking on arm/arm64 with defconfigs, and on x86/x86_64
with allyesconfig/allmodconfig is enough evidence that this
is mandatory nowadays.

So, remove optional from Python and add a quick description
about where it is required, leaving it open to one's imagination
that it could break with other configs we didn't map.

---
v2: drop support for 2.7, updated a comment and updated changes.rst.

Mauro Carvalho Chehab (2):
  docs: kernel-doc: avoid script crash on ancient Python
  docs: changes: better document Python needs

 Documentation/process/changes.rst |  9 +++++++-
 scripts/kernel-doc.py             | 34 ++++++++++++++++++++++---------
 2 files changed, 32 insertions(+), 11 deletions(-)

-- 
2.49.0

[PATCH v2 2/2] docs: changes: better document Python needs

[Mauro Carvalho Chehab]

Python is listed as an optional dependency, but this is not
true, as:

1) arm (multi_v7_defconfig and other defconfigs) and arm64 defconfig
   needs it due to DRM_MSM dependencies;

2) CONFIG_LTO_CLANG runs a python script at scripts/Makefile.vmlinux_o;

3) kernel-doc is called during compilation when some DRM options
   like CONFIG_DRM_I915_WERROR are enabled;

4) allyesconfig/allmodconfig will enable CONFIG_* dependencies
   that needs it;

5) besides DRM, other subsystems seem to have logic calling *.py
   scripts.

So, better document that and change the dependency from optional
to mandatory to reflect the current needs.

Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
---
 Documentation/process/changes.rst | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/Documentation/process/changes.rst b/Documentation/process/changes.rst
index bccfa19b45df..4c9088e429c8 100644
--- a/Documentation/process/changes.rst
+++ b/Documentation/process/changes.rst
@@ -61,7 +61,7 @@ Sphinx\ [#f1]_         3.4.3            sphinx-build --version
 GNU tar                1.28             tar --version
 gtags (optional)       6.6.5            gtags --version
 mkimage (optional)     2017.01          mkimage --version
-Python (optional)      3.9.x            python3 --version
+Python                 3.9.x            python3 --version
 GNU AWK (optional)     5.1.0            gawk --version
 ====================== ===============  ========================================
 
@@ -154,6 +154,13 @@ Perl
 You will need perl 5 and the following modules: ``Getopt::Long``,
 ``Getopt::Std``, ``File::Basename``, and ``File::Find`` to build the kernel.
 
+Python
+------
+
+Several config options require it: it is required for arm/arm64
+default configs, CONFIG_LTO_CLANG, some DRM optional configs,
+the kernel-doc tool, and docs build (Sphinx), among others.
+
 BC
 --
 
-- 
2.49.0

Re: [PATCH v2 2/2] docs: changes: better document Python needs

[Akira Yokosawa]

On Tue, 29 Jul 2025 18:43:04 +0200, Mauro Carvalho Chehab wrote:
> Python is listed as an optional dependency, but this is not
> true, as:
> 
> 1) arm (multi_v7_defconfig and other defconfigs) and arm64 defconfig
>    needs it due to DRM_MSM dependencies;
> 
> 2) CONFIG_LTO_CLANG runs a python script at scripts/Makefile.vmlinux_o;
> 
> 3) kernel-doc is called during compilation when some DRM options
>    like CONFIG_DRM_I915_WERROR are enabled;
> 
> 4) allyesconfig/allmodconfig will enable CONFIG_* dependencies
>    that needs it;
> 
> 5) besides DRM, other subsystems seem to have logic calling *.py
>    scripts.
> 

OK. This sounds convincing enough.

> So, better document that and change the dependency from optional
> to mandatory to reflect the current needs.
> 
> Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
> ---
>  Documentation/process/changes.rst | 9 ++++++++-
>  1 file changed, 8 insertions(+), 1 deletion(-)
> 
> diff --git a/Documentation/process/changes.rst b/Documentation/process/changes.rst
> index bccfa19b45df..4c9088e429c8 100644
> --- a/Documentation/process/changes.rst
> +++ b/Documentation/process/changes.rst
> @@ -61,7 +61,7 @@ Sphinx\ [#f1]_         3.4.3            sphinx-build --version
>  GNU tar                1.28             tar --version
>  gtags (optional)       6.6.5            gtags --version
>  mkimage (optional)     2017.01          mkimage --version
> -Python (optional)      3.9.x            python3 --version
> +Python                 3.9.x            python3 --version
>  GNU AWK (optional)     5.1.0            gawk --version
>  ====================== ===============  ========================================
>  
> @@ -154,6 +154,13 @@ Perl
>  You will need perl 5 and the following modules: ``Getopt::Long``,
>  ``Getopt::Std``, ``File::Basename``, and ``File::Find`` to build the kernel.
>  
> +Python
> +------
> +
> +Several config options require it: it is required for arm/arm64
> +default configs, CONFIG_LTO_CLANG, some DRM optional configs,
> +the kernel-doc tool, and docs build (Sphinx), among others.
> +

Looks much better.  Feel free to add:

Acked-by: Akira Yokosawa <akiyks@gmail.com>

Thanks.

Re: [PATCH v2 2/2] docs: changes: better document Python needs

[Rob Herring]

On Tue, Jul 29, 2025 at 11:44 AM Mauro Carvalho Chehab
<mchehab+huawei@kernel.org> wrote:
>
> Python is listed as an optional dependency, but this is not
> true, as:
>
> 1) arm (multi_v7_defconfig and other defconfigs) and arm64 defconfig
>    needs it due to DRM_MSM dependencies;
>
> 2) CONFIG_LTO_CLANG runs a python script at scripts/Makefile.vmlinux_o;
>
> 3) kernel-doc is called during compilation when some DRM options
>    like CONFIG_DRM_I915_WERROR are enabled;
>
> 4) allyesconfig/allmodconfig will enable CONFIG_* dependencies
>    that needs it;
>
> 5) besides DRM, other subsystems seem to have logic calling *.py
>    scripts.
>
> So, better document that and change the dependency from optional
> to mandatory to reflect the current needs.
>
> Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
> ---
>  Documentation/process/changes.rst | 9 ++++++++-
>  1 file changed, 8 insertions(+), 1 deletion(-)

DT schema checks requires it too.

Acked-by: Rob Herring (Arm) <robh@kernel.org>

Re: [PATCH v2 0/2] Better handle and document Python needs for Kernel build

[Jonathan Corbet]

Mauro Carvalho Chehab <mchehab+huawei@kernel.org> writes:

> Hi Jon,
>
> It follows the second version of this small series. It contains
> missing patches from the python backward-compatibility series.

Applied, thanks.

jon