linux-kernel - Re: [PATCH v5 2/5] i2c: piix4: Depends on X86

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Message-ID: <CAMuHMdXtrJn0i5ehBSq85+gTZ7fmeeQ=r-8fzV4GRFvmgOY1DQ@mail.gmail.com>
Date: Tue, 10 Jun 2025 18:59:09 +0200
From: Geert Uytterhoeven <geert@...ux-m68k.org>
To: Hans de Goede <hansg@...nel.org>
Cc: Mario Limonciello <superm1@...nel.org>, Huacai Chen <chenhuacai@...nel.org>, 
	Borislav Petkov <bp@...en8.de>, Jean Delvare <jdelvare@...e.com>, Andi Shyti <andi.shyti@...nel.org>, 
	Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>, 
	Jonathan Corbet <corbet@....net>, Mario Limonciello <mario.limonciello@....com>, 
	Yazen Ghannam <yazen.ghannam@....com>, Thomas Gleixner <tglx@...utronix.de>, 
	Ingo Molnar <mingo@...hat.com>, Dave Hansen <dave.hansen@...ux.intel.com>, 
	"maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" <x86@...nel.org>, "H . Peter Anvin" <hpa@...or.com>, 
	Shyam Sundar S K <Shyam-sundar.S-k@....com>, 
	"open list:DOCUMENTATION" <linux-doc@...r.kernel.org>, open list <linux-kernel@...r.kernel.org>, 
	"open list:I2C/SMBUS CONTROLLER DRIVERS FOR PC" <linux-i2c@...r.kernel.org>, 
	"open list:AMD PMC DRIVER" <platform-driver-x86@...r.kernel.org>, Ingo Molnar <mingo@...nel.org>, 
	linux-mips@...r.kernel.org, loongarch@...ts.linux.dev
Subject: Re: [PATCH v5 2/5] i2c: piix4: Depends on X86

Hi Hans,

On Tue, 10 Jun 2025 at 16:55, Hans de Goede <hansg@...nel.org> wrote:
> On 10-Jun-25 16:53, Hans de Goede wrote:
> > On 10-Jun-25 16:12, Mario Limonciello wrote:
> >> On 6/10/2025 2:24 AM, Huacai Chen wrote:
> >>> On Tue, Jun 10, 2025 at 5:16 PM Geert Uytterhoeven <geert@...ux-m68k.org> wrote:
> >>>> On Wed, 23 Apr 2025 at 01:49, Mario Limonciello <superm1@...nel.org> wrote:
> >>>>> From: Mario Limonciello <mario.limonciello@....com>
> >>>>>
> >>>>> PIIX4 and compatible controllers are only for X86. As some headers are
> >>>>> being moved into x86 specific headers PIIX4 won't compile on non-x86.
> >>>>>
> >>>>> Suggested-by: Ingo Molnar <mingo@...nel.org>
> >>>>> Signed-off-by: Mario Limonciello <mario.limonciello@....com>
> >>>>
> >>>> Thanks for your patch, which is now commit 7e173eb82ae97175
> >>>> ("i2c: piix4: Make CONFIG_I2C_PIIX4 dependent on CONFIG_X86")
> >>>> in v6.16-rc1.
> >>>>
> >>>>> --- a/drivers/i2c/busses/Kconfig
> >>>>> +++ b/drivers/i2c/busses/Kconfig
> >>>>> @@ -200,7 +200,7 @@ config I2C_ISMT
> >>>>>
> >>>>>   config I2C_PIIX4
> >>>>>          tristate "Intel PIIX4 and compatible (ATI/AMD/Serverworks/Broadcom/SMSC)"
> >>>>> -       depends on PCI && HAS_IOPORT
> >>>>> +       depends on PCI && HAS_IOPORT && X86
> >>>>
> >>>> Are you sure this south-bridge is not used on non-x86 platforms?
> >>>> It is enabled in several non-x86 defconfigs:
> >>>>
> >>>>      arch/loongarch/configs/loongson3_defconfig:CONFIG_I2C_PIIX4=y
> >>>>      arch/mips/configs/ip27_defconfig:CONFIG_I2C_PIIX4=m
> >>>>      arch/mips/configs/loongson2k_defconfig:CONFIG_I2C_PIIX4=y
> >>>>      arch/mips/configs/loongson3_defconfig:CONFIG_I2C_PIIX4=y
> >>>>
> >>>> The loongarch and loongson entries are probably bogus, but I wouldn't
> >>>> be surprised if the SGI Onyx and Origin do use Intel south-bridges.
> >>> Loongson can use AMD SB700/SB800 south bridges, which have I2C_PIIX4.
> >>
> >> Well we could revert this patch, but it's going to be a compile failure because of 624b0d5696a89b138408d385899dd35372db324b and other patches that go on top of that.
> >>
> >> My current leaning is we make a dummy fch.h header for these archs with #defines for 0.
> >
> > Move "fch.h" to include/linux/platform/x86/ so that it is available on all arches
> > and if necessary ifdef out anything x86 specific in the C-code referencing it ?
>
> Correction that should be include/linux/platform_data/x86/

Is that a good location?
It is not x86-specific, and I see no platform_data (struct) definitions in
arch/x86/include/asm/amd/fch.h?

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