linux-kernel - Re: [PATCH v18 2/8] mfd: simple-mfd-i2c: Add a Kconfig name

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Message-ID: <CAKmqyKO2x0V6p8LVsgq54f1KcghVhW2jw6zmUOFxbf6Zh+0BNA@mail.gmail.com>
Date:   Mon, 21 Mar 2022 17:45:00 +1000
From:   Alistair Francis <alistair23@...il.com>
To:     Guenter Roeck <linux@...ck-us.net>
Cc:     Geert Uytterhoeven <geert@...ux-m68k.org>,
        Alistair Francis <alistair@...stair23.me>,
        Mark Brown <broonie@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Sascha Hauer <kernel@...gutronix.de>,
        Liam Girdwood <lgirdwood@...il.com>,
        Lee Jones <lee.jones@...aro.org>,
        Linux PM list <linux-pm@...r.kernel.org>,
        linux-hwmon@...r.kernel.org,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>, NXP Linux Team <linux-imx@....com>,
        Zhang Rui <rui.zhang@...el.com>,
        Amit Kucheria <amitk@...nel.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        Andreas Kemnade <andreas@...nade.info>,
        Sascha Hauer <s.hauer@...gutronix.de>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Shawn Guo <shawnguo@...nel.org>
Subject: Re: [PATCH v18 2/8] mfd: simple-mfd-i2c: Add a Kconfig name

On Sun, Mar 20, 2022 at 12:48 AM Guenter Roeck <linux@...ck-us.net> wrote:
>
> On 3/19/22 02:28, Geert Uytterhoeven wrote:
> > Hi Alistair,
> >
> > On Sat, Mar 19, 2022 at 3:36 AM Alistair Francis <alistair23@...il.com> wrote:
> >> On Tue, Mar 8, 2022 at 8:53 PM Geert Uytterhoeven <geert@...ux-m68k.org> wrote:
> >>> Thanks for your patch, which is now commit bae5a4acef67db88
> >>> ("mfd: simple-mfd-i2c: Add a Kconfig name") in mfd/for-mfd-next.
> >>>
> >>> On Mon, Jan 24, 2022 at 1:24 PM Alistair Francis <alistair@...stair23.me> wrote:
> >>>> Add a Kconfig name to the "Simple Multi-Functional Device support (I2C)"
> >>>> device so that it can be enabled via menuconfig.
> >>>
> >>> Which still does not explain why this would be needed...
> >>>
> >>>> Signed-off-by: Alistair Francis <alistair@...stair23.me>
> >>>> Acked-for-MFD-by: Lee Jones <lee.jones@...aro.org>
> >>>
> >>>> --- a/drivers/mfd/Kconfig
> >>>> +++ b/drivers/mfd/Kconfig
> >>>> @@ -1188,7 +1188,7 @@ config MFD_SI476X_CORE
> >>>>            module will be called si476x-core.
> >>>>
> >>>>   config MFD_SIMPLE_MFD_I2C
> >>>> -       tristate
> >>>> +       tristate "Simple Multi-Functional Device support (I2C)"
> >>>>          depends on I2C
> >>>>          select MFD_CORE
> >>>>          select REGMAP_I2C
> >>>
> >>> The help text states:
> >>>
> >>> | This driver creates a single register map with the intention for it
> >>> | to be shared by all sub-devices.
> >>>
> >>> Yes, that's what MFD does?
> >>>
> >>> | Once the register map has been successfully initialised, any
> >>> | sub-devices represented by child nodes in Device Tree will be
> >>> | subsequently registered.
> >>>
> >>> OK...?
> >>>
> >>> Still, no clue about what this driver really does, and why and when
> >>> it would be needed.
> >>>
> >>> There is one driver symbol that selects MFD_SIMPLE_MFD_I2C.
> >>> There are no driver symbols that depend on this symbol.
> >>>
> >>> If you have a driver in the pipeline that can make use of this,
> >>> can't it just select MFD_SIMPLE_MFD_I2C, so the symbol itself can
> >>> stay invisible?
> >>
> >> My patch "mfd: simple-mfd-i2c: Enable support for the silergy,sy7636a"
> >> allows using this driver for the silergy,sy7636a MFD. So it's nice to
> >> be able to enable and disable it as required.
> >
> > So after that patch, enabling MFD_SIMPLE_MFD_I2C will enable
> > support for an ever-growing random bunch of devices, none of which
> > is described in the help text?
> > To me, ghat doesn't look like the way to go forward...
> >
>
> I am probably missing something. Why not something like the following ?
>
> config MFD_SY7636A
>          tristate "Silergy SY7636A voltage regulator"
>          depends on I2C
>          select MFD_SIMPLE_MFD_I2C
>          help
>            Enable support for Silergy SY7636A voltage regulator.
>
>            To enable support for building sub-devices as modules,
>            choose M here.
>
>
> This would be quite similar to MFD_SL28CPLD which essentially does
> the same (and, unless I am missing something, doesn't have its own
> driver either). Sub-devices would then depend on MFD_SY7636A.

That's fine with me.

As you said this patch is already in the mfd/for-mfd-next tree, should
I resend the series?

Alistair

>
> Guenter
>
> > 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
>