linux-kernel - Re: [PATCH v4 06/11] gpio: add support for the sl28cpld GPIO controller

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Date:   Fri, 05 Jun 2020 14:42:53 +0200
From:   Michael Walle <michael@...le.cc>
To:     Andy Shevchenko <andy.shevchenko@...il.com>
Cc:     "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>,
        devicetree <devicetree@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-hwmon@...r.kernel.org, linux-pwm@...r.kernel.org,
        linux-watchdog@...r.kernel.org,
        linux-arm Mailing List <linux-arm-kernel@...ts.infradead.org>,
        Linus Walleij <linus.walleij@...aro.org>,
        Bartosz Golaszewski <bgolaszewski@...libre.com>,
        Rob Herring <robh+dt@...nel.org>,
        Jean Delvare <jdelvare@...e.com>,
        Guenter Roeck <linux@...ck-us.net>,
        Lee Jones <lee.jones@...aro.org>,
        Thierry Reding <thierry.reding@...il.com>,
        Uwe Kleine-König <u.kleine-koenig@...gutronix.de>,
        Wim Van Sebroeck <wim@...ux-watchdog.org>,
        Shawn Guo <shawnguo@...nel.org>, Li Yang <leoyang.li@....com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Jason Cooper <jason@...edaemon.net>,
        Marc Zyngier <maz@...nel.org>, Mark Brown <broonie@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Subject: Re: [PATCH v4 06/11] gpio: add support for the sl28cpld GPIO
 controller

Am 2020-06-05 14:00, schrieb Andy Shevchenko:
> On Fri, Jun 5, 2020 at 12:14 AM Michael Walle <michael@...le.cc> wrote:
> 
>> Add support for the GPIO controller of the sl28 board management
>> controller. This driver is part of a multi-function device.
>> 
>> A controller has 8 lines. There are three different flavors:
>> full-featured GPIO with interrupt support, input-only and output-only.
> 
> ...
> 
>> +#include <linux/of_device.h>
> 
> I think also not needed.
> But wait...
> 
>> +       return devm_regmap_add_irq_chip_np(dev, dev_of_node(dev), 
>> regmap,
> 
> It seems regmap needs to be converted to use fwnode.

Mhh, this _np functions was actually part of this series in the
beginning.

>> +                                          irq, IRQF_SHARED | 
>> IRQF_ONESHOT, 0,
>> +                                          irq_chip, &gpio->irq_data);
> 
> ...
> 
>> +       if (!pdev->dev.parent)
>> +               return -ENODEV;
> 
> Are we expecting to get shot into foot? I mean why we need this check?

Can we be sure, that we always have a parent node? You are the first
which complains about this ;) There were some other comments to move
this to the beginning of the function.

> 
>> +       dev_id = platform_get_device_id(pdev);
>> +       if (dev_id)
>> +               type = dev_id->driver_data;
> 
> Oh, no. In new code we don't need this. We have facilities to provide
> platform data in a form of fwnode.

Ok I'll look into that.

But I already have a question, so there are of_property_read_xx(), which
seems to be the old functions, then there is device_property_read_xx() 
and
fwnode_property_read_xx(). What is the difference between the latter 
two?

> 
>> +       else
>> +               type = 
>> (uintptr_t)of_device_get_match_data(&pdev->dev);
> 
> So does this. device_get_match_data().
ok

> 
>> +       if (!type)
>> +               return -ENODEV;
> 
> ...
> 
>> +       if (irq_support &&
> 
> Why do you need this flag? Can't simple IRQ number be sufficient?

I want to make sure, the is no misconfiguration. Eg. only GPIO
flavors which has irq_support set, have the additional interrupt
registers.

> 
>> +           device_property_read_bool(&pdev->dev, 
>> "interrupt-controller")) {
>> +               irq = platform_get_irq(pdev, 0);
>> +               if (irq < 0)
>> +                       return irq;
>> +
>> +               ret = sl28cpld_gpio_irq_init(&pdev->dev, gpio, regmap,
>> +                                            base, irq);
>> +               if (ret)
>> +                       return ret;
>> +
>> +               config.irq_domain = 
>> regmap_irq_get_domain(gpio->irq_data);
>> +       }
> 
> ...
> 
>> +static const struct of_device_id sl28cpld_gpio_of_match[] = {
> 
>> +       { .compatible = "kontron,sl28cpld-gpio",
>> +         .data = (void *)SL28CPLD_GPIO },
>> +       { .compatible = "kontron,sl28cpld-gpi",
>> +         .data = (void *)SL28CPLD_GPI },
>> +       { .compatible = "kontron,sl28cpld-gpo",
>> +         .data = (void *)SL28CPLD_GPO },
> 
> All above can be twice less LOCs.

They are longer than 80 chars. Or do I miss something?

> 
>> +       {},
> 
> No comma.

ok

>> +};
> 
> 
> ...
> 
>> +               .name = KBUILD_MODNAME,
> 
> This actually not good idea in long term. File name can change and 
> break an ABI.

Ahh an explanation, why this is bad. Ok makes sense, although to be 
fair,
.id_table should be used for the driver name matching. I'm not sure if
this is used somewhere else, though.


-- 
-michael