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

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Date:   Sat, 06 Nov 2021 00:19:51 +0100
From:   Michael Walle <michael@...le.cc>
To:     Robert Marko <robert.marko@...tura.hr>
Cc:     Andy Shevchenko <andy.shevchenko@...il.com>,
        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

Am 2021-11-05 12:34, schrieb Robert Marko:
> 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?

I guess this was already clarified? Because you don't set
all the properties of the config you have to initialize it.
Otherwise anything could happen.

-michael