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

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Date:   Sat, 19 Mar 2022 12:36:11 +1000
From:   Alistair Francis <alistair23@...il.com>
To:     Geert Uytterhoeven <geert@...ux-m68k.org>
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

On Tue, Mar 8, 2022 at 8:53 PM Geert Uytterhoeven <geert@...ux-m68k.org> wrote:
>
> Hi Alistair,
>
> 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.

Alistair

>
> Thanks!
>
> 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