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From:   Geert Uytterhoeven <geert@linux-m68k.org>
Date:   Thu, 2 Mar 2023 11:44:02 +0100
Message-ID: <CAMuHMdVSJADwTSkOD2mG2yU0XeFd0QAUjojQDz5phWhkRcLGOg@mail.gmail.com>
Subject: Re: [PATCH v4 00/24] Remove COMMAND_LINE_SIZE from uapi
To:     Alexandre Ghiti <alex@ghiti.fr>
Cc:     Alexandre Ghiti <alexghiti@rivosinc.com>,
        Jonathan Corbet <corbet@lwn.net>,
        Richard Henderson <richard.henderson@linaro.org>,
        Ivan Kokshaysky <ink@jurassic.park.msu.ru>,
        Matt Turner <mattst88@gmail.com>,
        Vineet Gupta <vgupta@kernel.org>,
        Russell King <linux@armlinux.org.uk>,
        Catalin Marinas <catalin.marinas@arm.com>,
        Will Deacon <will@kernel.org>,
        Huacai Chen <chenhuacai@kernel.org>,
        WANG Xuerui <kernel@xen0n.name>,
        Michal Simek <monstr@monstr.eu>,
        Thomas Bogendoerfer <tsbogend@alpha.franken.de>,
        "James E . J . Bottomley" <James.Bottomley@hansenpartnership.com>,
        Helge Deller <deller@gmx.de>,
        Michael Ellerman <mpe@ellerman.id.au>,
        Nicholas Piggin <npiggin@gmail.com>,
        Christophe Leroy <christophe.leroy@csgroup.eu>,
        Paul Walmsley <paul.walmsley@sifive.com>,
        Palmer Dabbelt <palmer@dabbelt.com>,
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        "H . Peter Anvin" <hpa@zytor.com>, Chris Zankel <chris@zankel.net>,
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        linux-s390@vger.kernel.org, linux-sh@vger.kernel.org,
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Hi Alex,

On Thu, Mar 2, 2023 at 11:09 AM Alexandre Ghiti <alex@ghiti.fr> wrote:
> On 3/2/23 10:47, Geert Uytterhoeven wrote:
> > On Thu, Mar 2, 2023 at 10:35 AM Alexandre Ghiti <alexghiti@rivosinc.com> wrote:
> >> This all came up in the context of increasing COMMAND_LINE_SIZE in the
> >> RISC-V port.  In theory that's a UABI break, as COMMAND_LINE_SIZE is the
> >> maximum length of /proc/cmdline and userspace could staticly rely on
> >> that to be correct.
> >>
> >> Usually I wouldn't mess around with changing this sort of thing, but
> >> PowerPC increased it with a5980d064fe2 ("powerpc: Bump COMMAND_LINE_SIZE
> >> to 2048").  There are also a handful of examples of COMMAND_LINE_SIZE
> >> increasing, but they're from before the UAPI split so I'm not quite sure
> >> what that means: e5a6a1c90948 ("powerpc: derive COMMAND_LINE_SIZE from
> >> asm-generic"), 684d2fd48e71 ("[S390] kernel: Append scpdata to kernel
> >> boot command line"), 22242681cff5 ("MIPS: Extend COMMAND_LINE_SIZE"),
> >> and 2b74b85693c7 ("sh: Derive COMMAND_LINE_SIZE from
> >> asm-generic/setup.h.").
> >>
> >> It seems to me like COMMAND_LINE_SIZE really just shouldn't have been
> >> part of the uapi to begin with, and userspace should be able to handle
> >> /proc/cmdline of whatever length it turns out to be.  I don't see any
> >> references to COMMAND_LINE_SIZE anywhere but Linux via a quick Google
> >> search, but that's not really enough to consider it unused on my end.
> >>
> >> This issue was already considered in s390 and they reached the same
> >> conclusion in commit 622021cd6c56 ("s390: make command line
> >> configurable").
> >>
> >> The feedback on the v1 seemed to indicate that COMMAND_LINE_SIZE really
> >> shouldn't be part of uapi, so this now touches all the ports.  I've
> >> tried to split this all out and leave it bisectable, but I haven't
> >> tested it all that aggressively.
> >>
> >> Changes since v3 <https://lore.kernel.org/all/20230214074925.228106-1-alexghiti@rivosinc.com/>:
> >> * Added RB/AB
> >> * Added a mention to commit 622021cd6c56 ("s390: make command line
> >>    configurable") in the cover letter
> > Thanks for the update!
> >
> >   Apparently you forgot to add your own SoB?
>
> I do not know, should I? Palmer did all the work, I only fixed 3 minor
> things

If you are picking up patches, and submitting them to someone else
for upstream inclusion, you should add your own SoB.
https://elixir.bootlin.com/linux/latest/source/Documentation/process/submitting-patches.rst#L419

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-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