linux-kernel - Re: [PATCH v2 12/18] gpio: madera: Support Cirrus Logic Madera class codecs

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Message-ID: <1493131461.4826.66.camel@rf-debian.wolfsonmicro.main>
Date:   Tue, 25 Apr 2017 15:44:21 +0100
From:   Richard Fitzgerald <rf@...nsource.wolfsonmicro.com>
To:     Linus Walleij <linus.walleij@...aro.org>
CC:     Lee Jones <lee.jones@...aro.org>, Mark Brown <broonie@...nel.org>,
        Alexandre Courbot <gnurou@...il.com>,
        Rob Herring <robh+dt@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Jason Cooper <jason@...edaemon.net>,
        "alsa-devel@...a-project.org" <alsa-devel@...a-project.org>,
        "open list:WOLFSON MICROELECTRONICS DRIVERS" 
        <patches@...nsource.wolfsonmicro.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>
Subject: Re: [PATCH v2 12/18] gpio: madera: Support Cirrus Logic Madera
 class codecs

On Tue, 2017-04-25 at 16:13 +0200, Linus Walleij wrote:
> On Mon, Apr 24, 2017 at 6:08 PM, Richard Fitzgerald
> <rf@...nsource.wolfsonmicro.com> wrote:
> 
> > This adds support for the GPIOs on Cirrus Logic Madera class codecs.
> > Any pins not used for special functions (see the pinctrl driver) can be
> > used as general single-bit input or output lines. The number of available
> > GPIOs varies between codecs.
> >
> > Signed-off-by: Nariman Poushin <nariman@...nsource.wolfsonmicro.com>
> > Signed-off-by: Richard Fitzgerald <rf@...nsource.wolfsonmicro.com>
> > Signed-off-by: Charles Keepax <ckeepax@...nsource.wolfsonmicro.com>
> > ---
> > Changes from V1:
> > - dt bindings moved to a separate patch
> > - dependent on pinctrl driver instead of parent MFD
> > - added get_direction function
> > - added .request / .free / .set_config to work with pinctrl driver
> > - register range with pinctrl driver
> 
> Nice, but...
> 
> > +       ret = gpiochip_add_pin_range(&madera_gpio->gpio_chip, "madera-pinctrl",
> > +                                    0, 0, madera_gpio->gpio_chip.ngpio);
> > +       if (ret) {
> > +               dev_warn(&pdev->dev, "Failed to add pin range (%d)\n", ret);
> > +               return ret;
> > +       }
> 
> This is all fine, but we have generic code for adding ranges from
> the device tree, see
> Documentation/devicetree/bindings/gpio/gpio.txt
> 

The range of gpio pins is a fixed property of the chip, and so is the
combination of gpio+pinctrl drivers.

I think the general principle of the DT maintainers is that DT should be
used for things that the drivers don't already know and can't figure
out.

> With that this range should not even be needed.
> Apart from that it looks pretty solid.
> 
> Yours,
> Linus Walleij