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

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Message-ID: <CAMuHMdVy4E1pX+VLLq_05FX4pM+BPZycQgn68ArGh2s8qL24=w@mail.gmail.com>
Date:   Sat, 19 Mar 2022 10:28:26 +0100
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     Alistair Francis <alistair23@...il.com>
Cc:     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

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...

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