[PATCH v3 0/2] Don't create Python bytecode when building the kernel

[Andy Shevchenko]

On Mon, Apr 21, 2025 at 10:35:29AM -0600, Jonathan Corbet wrote:
> Dmitry Baryshkov <dmitry.baryshkov at oss.qualcomm.com> writes:
> > On Wed, Apr 16, 2025 at 03:51:03PM +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.
> >
> > Would it be possible to properly support O= and create pyc / pycache
> > inside the object/output dir?
> 
> I have to confess, I've been wondering if we should be treating the .pyc
> files like we treat .o files or other intermediate products.  Rather
> than trying to avoid their creation entirely, perhaps we should just be
> sure they end up in the right place and are properly cleaned up...?
> 
> To answer Dmitry's question, it seems that setting PYTHONPYCACHEPREFIX
> should do the trick?

It's not so easy. The Python is written in a way that it thinks it will never
runs object files separately from the source. Hence that variable sets only
the folder per script as _home_ for the cache. It's completely unusable. They
took it wrong. It still can be _painfully_ used, but it will make Makefiles
uglier.

-- 
With Best Regards,
Andy Shevchenko