linux-kernel - Re: [PATCH 2/2] docs: changes: better document Python needs

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Message-ID: <20250729153709.4040236a@sal.lan>
Date: Tue, 29 Jul 2025 15:37:09 +0200
From: Mauro Carvalho Chehab <mchehab+huawei@...nel.org>
To: Akira Yokosawa <akiyks@...il.com>
Cc: corbet@....net, linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
 workflows@...r.kernel.org, Laurent Pinchart
 <laurent.pinchart@...asonboard.com>, Jani Nikula <jani.nikula@...el.com>
Subject: Re: [PATCH 2/2] docs: changes: better document Python needs

Em Tue, 29 Jul 2025 19:35:57 +0900
Akira Yokosawa <akiyks@...il.com> escreveu:

> [+CC Laurent and Jani]
> 
> Hi,
> 
> On Mon, 28 Jul 2025 16:54:29 +0200, Mauro Carvalho Chehab wrote:
> > Python is listed as an optional dependency, but this is not
> > true, as:
> > 
> > 1) CONFIG_LTO_CLANG runs a python script at scripts/Makefile.vmlinux_o;
> > 
> > 2) kernel-doc is called during compilation when some DRM options
> >    like CONFIG_DRM_I915_WERROR are enabled;
> > 
> > 3) allyesconfig/allmodconfig will enable both.  
> 
> Well, these conditions still sound to me optional.

Then we agree to disagree: if a missing package prevents building
the kernel with allyesconfig/allmodconfig, IMO it is mandatory.

In any case, as Jani pointed out, DRM_MSM, which is part of arm
default configs also require Python. Building with clang also
requires it on several archs. There are other parts that
seem to require it, but I didn't dig into it.

So, IMHO, even if you consider allmodconfig/allyesconfig as
"optional", and you also consider clang as "optional" (it is marked
as optional at changes), it is still mandatory for arm 32-bit most
common  config (multi_v7_defconfig) and for arm64 defconfig.

It sounds pretty much mandatory to me: if a distro doesn't have
it, it can't support arm architectures.

IMO, it should not be tagged as optional there. At max, a note
under Python description could mention what scenarios one still
may not have it.

Now, adding a note like that means that someone would need to be
periodically updating it when people add more auto-generated
stuff that may require it.

> > So, better document that.
> > 
> > Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@...nel.org>
> > ---
> >  Documentation/process/changes.rst | 13 ++++++++++++-
> >  1 file changed, 12 insertions(+), 1 deletion(-)
> > 
> > diff --git a/Documentation/process/changes.rst b/Documentation/process/changes.rst
> > index bccfa19b45df..f6abecf6da86 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 +154,17 @@ Perl
> >  You will need perl 5 and the following modules: ``Getopt::Long``,
> >  ``Getopt::Std``, ``File::Basename``, and ``File::Find`` to build the kernel.
> >  
> > +Python
> > +------
> > +
> > +CONFIG_LTO_CLANG requires python 2.7 or 3.0+; some DRM config options like
> > +CONFIG_DRM_I915_WERROR require at least Python 2.7 or 3.4+.
> > +
> > +The kernel-doc tool and docs build require at least 3.6, but they depend on
> > +dict changes that happened on 3.7 to produce valid results.
> > +
> > +Other tools within the Kernel tree require newer versions.
> > +  
> 
> These details look confusing in changes.rst.  The table above says
> python >=3.9.x.  All you need to say here would just something lile:
> 
> +Python
> +------
> +
> +Required with CONFIG_LTO_CLANG, some DRM config options like
> +CONFIG_DRM_I915_WERROR, the kernel-doc tool, and docs build (Sphinx),
> +among others.
> 
> Other details can go to comments in each script or other docs if
> necessary.

Maybe something like:

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.

Regards,
Mauro