linux-kernel - Re: [PATCH v4 03/14] pinctrl-ingenic: add a pinctrl driver for the Ingenic jz47xx SoCs

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Message-ID: <20170407105629.n6a2cxt3pof66gu2@dell>
Date:   Fri, 7 Apr 2017 11:56:29 +0100
From:   Lee Jones <lee.jones@...aro.org>
To:     Linus Walleij <linus.walleij@...aro.org>
Cc:     Paul Cercueil <paul@...pouillou.net>,
        Alexandre Courbot <gnurou@...il.com>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Ralf Baechle <ralf@...ux-mips.org>,
        Boris Brezillon <boris.brezillon@...e-electrons.com>,
        Thierry Reding <thierry.reding@...il.com>,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
        Maarten ter Huurne <maarten@...ewalker.org>,
        Lars-Peter Clausen <lars@...afoo.de>,
        Paul Burton <paul.burton@...tec.com>,
        James Hogan <james.hogan@...tec.com>,
        "linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Linux MIPS <linux-mips@...ux-mips.org>,
        "linux-mmc@...r.kernel.org" <linux-mmc@...r.kernel.org>,
        "linux-mtd@...ts.infradead.org" <linux-mtd@...ts.infradead.org>,
        "linux-pwm@...r.kernel.org" <linux-pwm@...r.kernel.org>,
        "linux-fbdev@...r.kernel.org" <linux-fbdev@...r.kernel.org>
Subject: Re: [PATCH v4 03/14] pinctrl-ingenic: add a pinctrl driver for the
 Ingenic jz47xx SoCs

On Fri, 07 Apr 2017, Linus Walleij wrote:

> On Sun, Apr 2, 2017 at 10:42 PM, Paul Cercueil <paul@...pouillou.net> wrote:
> 
> > This driver handles pin configuration and pin muxing for the
> > JZ4740 and JZ4780 SoCs from Ingenic.
> >
> > Signed-off-by: Paul Cercueil <paul@...pouillou.net>
> (...)
> > +       select MFD_CORE
> (...)
> > +#include <linux/mfd/core.h>
> 
> That's unorthodox. Still quite pretty!
> I would nee Lee Jones to say something about this, as it is
> essentially hijacking MFD into the pinctrl subsystem.
> 
> > +static struct mfd_cell ingenic_pinctrl_mfd_cells[] = {
> > +       {
> > +               .id = 0,
> > +               .name = "GPIOA",
> > +               .of_compatible = "ingenic,gpio-bank-a",
> > +       },
> > +       {
> > +               .id = 1,
> > +               .name = "GPIOB",
> > +               .of_compatible = "ingenic,gpio-bank-b",
> > +       },
> > +       {
> > +               .id = 2,
> > +               .name = "GPIOC",
> > +               .of_compatible = "ingenic,gpio-bank-c",
> > +       },
> > +       {
> > +               .id = 3,
> > +               .name = "GPIOD",
> > +               .of_compatible = "ingenic,gpio-bank-d",
> > +       },
> > +       {
> > +               .id = 4,
> > +               .name = "GPIOE",
> > +               .of_compatible = "ingenic,gpio-bank-e",
> > +       },
> > +       {
> > +               .id = 5,
> > +               .name = "GPIOF",
> > +               .of_compatible = "ingenic,gpio-bank-f",
> > +       },
> > +};
> (...)
> > +       err = devm_mfd_add_devices(dev, 0, ingenic_pinctrl_mfd_cells,
> > +                       ARRAY_SIZE(ingenic_pinctrl_mfd_cells), NULL, 0, NULL);
> > +       if (err) {
> > +               dev_err(dev, "Failed to add MFD devices\n");
> > +               return err;
> > +       }
> 
> I guess the alternative would be to reimplement the MFD structure.
> 
> Did you check the approach to use "simple-mfd" and just let the subnodes
> spawn as devices that way? I guess you did and this adds something
> necessary.

I'd like to hear what the OP has to say about why this is necessary.
However, as a first glimpse, I'm dead against exporting MFD
functionality to outside of the subsystem.

-- 
Lee Jones
Linaro STMicroelectronics Landing Team Lead
Linaro.org │ Open source software for ARM SoCs
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