linux-kernel - Re: [PATCH v7 2/6] gpio: Add Delta TN48M CPLD GPIO driver

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Date:   Fri, 5 Nov 2021 12:34:08 +0100
From:   Robert Marko <robert.marko@...tura.hr>
To:     Andy Shevchenko <andy.shevchenko@...il.com>,
        Michael Walle <michael@...le.cc>
Cc:     Linus Walleij <linus.walleij@...aro.org>,
        Bartosz Golaszewski <bgolaszewski@...libre.com>,
        Rob Herring <robh+dt@...nel.org>,
        Lee Jones <lee.jones@...aro.org>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>,
        devicetree <devicetree@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v7 2/6] gpio: Add Delta TN48M CPLD GPIO driver

On Tue, Nov 2, 2021 at 8:28 PM Andy Shevchenko
<andy.shevchenko@...il.com> wrote:
>
> On Tue, Nov 2, 2021 at 6:57 PM Robert Marko <robert.marko@...tura.hr> wrote:
> >
> > Delta TN48M switch has an onboard Lattice CPLD that is used as a GPIO
> > expander.
> >
> > The CPLD provides 12 pins in total on the TN48M, but on more advanced
> > switch models it provides up to 192 pins, so the driver is extendable
> > to support more switches.
>
> ...
>
> > +static int tn48m_gpio_probe(struct platform_device *pdev)
> > +{
>
> > +       const struct tn48m_gpio_config *gpio_config = NULL;
> > +       struct gpio_regmap_config config = {0};
>
> I don't see a point in assigning these variables.

Hi,
The NULL one isn't required, but the regmap one is, otherwise the
devm_gpio_regmap_register call will
return -EINVAL.

It will fail here:
https://elixir.bootlin.com/linux/latest/source/drivers/gpio/gpio-regmap.c#L209

I see that Michael Walle who did the GPIO regmap uses it as well in
the Kontron CPLD driver.
Michael, can you shed some light on this?

Regards,
Robert
>
> > +       struct regmap *regmap;
> > +       u32 base;
> > +       int ret;
> > +
> > +       if (!pdev->dev.parent)
> > +               return -ENODEV;
> > +
> > +       gpio_config = device_get_match_data(&pdev->dev);
> > +       if (!gpio_config)
> > +               return -ENODEV;
> > +
> > +       ret = device_property_read_u32(&pdev->dev, "reg", &base);
> > +       if (ret)
> > +               return ret;
> > +
> > +       regmap = dev_get_regmap(pdev->dev.parent, NULL);
> > +       if (!regmap)
> > +               return -ENODEV;
>
> > +}
>
> --
> With Best Regards,
> Andy Shevchenko



-- 
Robert Marko
Staff Embedded Linux Engineer
Sartura Ltd.
Lendavska ulica 16a
10000 Zagreb, Croatia
Email: robert.marko@...tura.hr
Web: www.sartura.hr