linux-kernel - Re: [PATCH 0/6] Add an asm-generic cpuinfo

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Date:   Mon, 22 Aug 2022 11:36:51 +0200
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     Conor Dooley <mail@...chuod.ie>
Cc:     Michal Simek <monstr@...str.eu>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        Heiko Carstens <hca@...ux.ibm.com>,
        Vasily Gorbik <gor@...ux.ibm.com>,
        Alexander Gordeev <agordeev@...ux.ibm.com>,
        Christian Borntraeger <borntraeger@...ux.ibm.com>,
        Sven Schnelle <svens@...ux.ibm.com>,
        Yoshinori Sato <ysato@...rs.sourceforge.jp>,
        Rich Felker <dalias@...c.org>,
        "David S . Miller" <davem@...emloft.net>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        "the arch/x86 maintainers" <x86@...nel.org>,
        "H . Peter Anvin" <hpa@...or.com>, Arnd Bergmann <arnd@...db.de>,
        Conor Dooley <conor.dooley@...rochip.com>,
        Kees Cook <keescook@...omium.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-riscv <linux-riscv@...ts.infradead.org>,
        linux-s390 <linux-s390@...r.kernel.org>,
        Linux-sh list <linux-sh@...r.kernel.org>,
        sparclinux <sparclinux@...r.kernel.org>,
        Linux-Arch <linux-arch@...r.kernel.org>
Subject: Re: [PATCH 0/6] Add an asm-generic cpuinfo_op declaration

Hi Conor,

On Sun, Aug 21, 2022 at 1:36 PM Conor Dooley <mail@...chuod.ie> wrote:
> From: Conor Dooley <conor.dooley@...rochip.com>
>
> RISC-V is missing a prototype for cpuinfo_op. Rather than adding yet
> another `extern const struct seq_operations cpuinfo_op;` to an arch
> specific header file, create an asm-generic variant and migrate the
> existing arch variants there too. Obv. there are other archs that use
> cpuinfo_op but don't declare it and surely also have the same warning?
> I went for the minimum change here, but would be perfectly happy to
> extend the change to all archs if this change is worthwhile. Or just
> make a header in arch/riscv, any of the three work for me!
>
> If this isn't the approach I should've gone for, any direction would
> be great :) I tried pushing this last weekend to get LKP to test it but
> I got neither a build success nor a build failure email from it, so
> I figured I may as well just send the patches..
>
> I wasn't too sure if this could be a single patch, so I split it out
> into a patch fixing the issue on RISC-V & copy-paste patches for each
> arch that I moved.

Thanks for your series!

> Conor Dooley (6):
>   asm-generic: add a cpuinfo_ops definition in shared code
>   microblaze: use the asm-generic version of cpuinfo_op
>   s390: use the asm-generic version of cpuinfo_op
>   sh: use the asm-generic version of cpuinfo_op
>   sparc: use the asm-generic version of cpuinfo_op
>   x86: use the asm-generic version of cpuinfo_op
>
>  arch/microblaze/include/asm/processor.h | 2 +-
>  arch/riscv/include/asm/processor.h      | 1 +
>  arch/s390/include/asm/processor.h       | 2 +-
>  arch/sh/include/asm/processor.h         | 2 +-
>  arch/sparc/include/asm/cpudata.h        | 3 +--
>  arch/x86/include/asm/processor.h        | 2 +-
>  include/asm-generic/processor.h         | 7 +++++++
>  7 files changed, 13 insertions(+), 6 deletions(-)
>  create mode 100644 include/asm-generic/processor.h

I was a bit surprised not to find fs/proc/cpuinfo.c in the diffstat
above. That file already has an external declaration for cpuinfo_op,
and uses it rather unconditionally (that is, if CONFIG_PROC_FS=y)
on all architectures.

So I think you can just move that to include/linux/processor.h, include
the latter everywhere, and drop all architecture-specific copies.

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds