Re: [TECH TOPIC] Kernel documentation - update and future directions

[Johannes Berg <johannes@sipsolutions.net>]

On Wed, 2025-09-03 at 16:57 +0200, Mauro Carvalho Chehab wrote:
> There are actually 3 different issues that depend on python version:
> 
> 1. sphinx-pre-install:
> 
>     This used to be a Perl script. The goal is to check if sphinx-build
>     is installed and works, and identify missing dependencies.
> 
>     The problem is: if one installs python3xx-Sphinx, instead of
>     python3-Sphinx, the script will fail, except if it first switches
>     to python3.xx;

So let it fail. Fail is fine, at least it's a clear signal. The python3-
Spinx package will anyway be a sort of meta-package that's basically
empty and depends on a specific version.

> 2. sphinx-build logic inside makefile, required for doc-specific targets:
> 
>    - If python < 3.7, doc builds fail;

Fine, python 3.7 is really old by now, if you actually have python3==3.7
you probably have other problems anyway. I don't think we need to
support that.

>    - If python3xx-Sphinx is installed, build only works if started using
>      the right python3.xx exec

Yeah, but again, we can require python3-sphinx here.

> Now, for (1) and (2), it should be possible to allow building docs even
> if the distro requires Python < 3.7, providing extra packages for newer
> Python, as almost all distros do. See, several distros require python
> on their minimal install images, because it can be using during package
> install. Removing the default python replacing by a new version may break
> the system, as the newer version may not be backward-compatible.

Umm, no? I'm not sure there's a need to cater to truly ancient software
in today's kernel build environment. Even debian *oldoldstable* has
python3==3.9:
https://packages.debian.org/bullseye/python3

> The best alternative seems to check if:
> 
> - python version is bellow the minimal supported version;
> - there is a newer python binary at PATH;
> - check if sphinx-build runs with the newest version.
> 
> If all those 3 conditions are met, build docs with a version that works,
> printing a message to tell the user what Python binary was used.

I still disagree. The only predictable thing is to use "python3" and
associated python3-xyz tools, and let things fail if those versions are
too old.

Picking a random different version that will depend on the kernel
version etc. is just going to introduce more moving parts and will
eventually be painful.

johannes