linux-kernel - Re: [PATCH 2/6] scripts/crc: add gen-crc-consts.py

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Message-ID: <CAMj1kXGH77pHUOt1s2qatAz7sHAXzFTcbx5rbtwnRBPCgAnFyg@mail.gmail.com>
Date: Fri, 29 Nov 2024 19:33:53 +0100
From: Ard Biesheuvel <ardb@...nel.org>
To: Eric Biggers <ebiggers@...nel.org>
Cc: linux-kernel@...r.kernel.org, linux-crypto@...r.kernel.org, x86@...nel.org
Subject: Re: [PATCH 2/6] scripts/crc: add gen-crc-consts.py

On Fri, 29 Nov 2024 at 18:47, Eric Biggers <ebiggers@...nel.org> wrote:
>
> On Fri, Nov 29, 2024 at 05:09:51PM +0100, Ard Biesheuvel wrote:
> > On Mon, 25 Nov 2024 at 05:12, Eric Biggers <ebiggers@...nel.org> wrote:
> > >
> > > From: Eric Biggers <ebiggers@...gle.com>
> > >
> > > Add a Python script that generates constants for computing the given CRC
> > > variant(s) using x86's pclmulqdq or vpclmulqdq instructions.
> > >
> >
> > There is nothing x86 specific about this, right? Except perhaps the
> > choice of fold distances?
>
> Yes, and maybe other architectures will want something different for bswap_mask
> and shuf_table depending on exactly what instructions they have.  But it should
> be straightforward to add an option to generate another arch's variant.
>
> > > +print('/* SPDX-License-Identifier: GPL-2.0-or-later */')
> >
> > Does it make sense to add a GPL header into a generated file?
>
> Since I'm checking in the generated file, I figured it would run up against the
> policy that every source file must have a license.
>
> We could generate the file during every build, but I don't really want to deal
> with complaints about Python not being installed or Python being too old, or to
> put the performance of the script on the critical path for almost everyone
> building a kernel for x86.  (Note that Documentation/process/changes.rst
> currently lists Python as "optional" for building the kernel, not required.)
>

Fair enough.