linux-kernel - Re: [PATCH v4 1/3] lib/vsprintf: Add support for generic FourCCs by extending %p4cc

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Message-ID: <CAMuHMdXuM5wBoAeJXK+rTp5Ok8U87NguVGm+dng5WOWaP3O54w@mail.gmail.com>
Date: Tue, 22 Apr 2025 12:32:42 +0200
From: Geert Uytterhoeven <geert@...ux-m68k.org>
To: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc: Aditya Garg <gargaditya08@...e.com>, Hector Martin <marcan@...can.st>, alyssa@...enzweig.io, 
	Petr Mladek <pmladek@...e.com>, Sven Peter <sven@...npeter.dev>, 
	Thomas Zimmermann <tzimmermann@...e.de>, Aun-Ali Zaidi <admin@...eit.net>, 
	Maxime Ripard <mripard@...nel.org>, airlied@...hat.com, Simona Vetter <simona@...ll.ch>, 
	Steven Rostedt <rostedt@...dmis.org>, Rasmus Villemoes <linux@...musvillemoes.dk>, 
	Sergey Senozhatsky <senozhatsky@...omium.org>, Jonathan Corbet <corbet@....net>, 
	Andrew Morton <akpm@...ux-foundation.org>, apw@...onical.com, joe@...ches.com, 
	dwaipayanray1@...il.com, lukas.bulwahn@...il.com, Kees Cook <kees@...nel.org>, 
	tamird@...il.com, Linux Kernel Mailing List <linux-kernel@...r.kernel.org>, 
	dri-devel@...ts.freedesktop.org, linux-doc@...r.kernel.org, 
	Asahi Linux Mailing List <asahi@...ts.linux.dev>, netdev <netdev@...r.kernel.org>
Subject: Re: [PATCH v4 1/3] lib/vsprintf: Add support for generic FourCCs by
 extending %p4cc

Hi Andy,

On Tue, 22 Apr 2025 at 12:16, Andy Shevchenko
<andriy.shevchenko@...ux.intel.com> wrote:
> On Tue, Apr 22, 2025 at 10:43:59AM +0200, Geert Uytterhoeven wrote:
> > On Tue, 22 Apr 2025 at 10:30, Aditya Garg <gargaditya08@...e.com> wrote:
> > > On 22-04-2025 01:37 pm, Geert Uytterhoeven wrote:
> > > > On Tue, 8 Apr 2025 at 08:48, Aditya Garg <gargaditya08@...e.com> wrote:
>
> ...
>
> > > Originally, it was %p4cr (reverse-endian), but on the request of the
> > > maintainers, it was changed to %p4cn.
> >
> > Ah, I found it[1]:
> >
> > | so, it needs more information that this mimics htonl() / ntohl() for
> > networking.
> >
> > IMHO this does not mimic htonl(), as htonl() is a no-op on big-endian.
> > while %p4ch and %p4cl yield different results on big-endian.
> >
> > > So here network means reverse of host, not strictly big-endian.
> >
> > Please don't call it "network byte order" if that does not have the same
> > meaning as in the network subsystem.
> >
> > Personally, I like "%p4r" (reverse) more...
> > (and "%p4ch" might mean human-readable ;-)
>
> It will confuse the reader. h/r is not very established pair. If you really
> wont see h/n, better to drop them completely for now then. Because I'm against
> h/r pair.

I am not against h/n in se, but I am against bad/confusing naming.
The big question is: should it print
  (A) the value in network byte order, or
  (B) the reverse of host byte order?

If the answer is (A), I see no real reason to have %p4n, as %p4b prints
the exact same thing.  Moreover, it leaves us without a portable
way to print values in reverse without the caller doing an explicit
__swab32() (which is not compatible with the %p pass-by-pointer
calling convention).

If the answer is (B), "%p4n using network byte order" is bad/confusing
naming.

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