linux-kernel - Re: [PATCH v5 09/19] gpio: support ROHM BD71815 GPOs

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Date:   Tue, 30 Mar 2021 13:11:39 +0300
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Matti Vaittinen <matti.vaittinen@...rohmeurope.com>
Cc:     Lee Jones <lee.jones@...aro.org>, Rob Herring <robh+dt@...nel.org>,
        Linus Walleij <linus.walleij@...aro.org>,
        Bartosz Golaszewski <bgolaszewski@...libre.com>,
        devicetree <devicetree@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-power <linux-power@...rohmeurope.com>,
        "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>
Subject: Re: [PATCH v5 09/19] gpio: support ROHM BD71815 GPOs

On Mon, Mar 29, 2021 at 3:58 PM Matti Vaittinen
<matti.vaittinen@...rohmeurope.com> wrote:
>
> Support GPO(s) found from ROHM BD71815 power management IC. The IC has two
> GPO pins but only one is properly documented in data-sheet. The driver

in the datasheet

> exposes by default only the documented GPO. The second GPO is connected to
> E5 pin and is marked as GND in data-sheet. Control for this undocumented

in the datasheet

> pin can be enabled using a special DT property.
>
> This driver is derived from work by Peter Yang <yanglsh@...est-tech.com>
> although not so much of original is left.

of the original

It seems you ignored my comments about the commit message. :-(



> +struct bd71815_gpio {
> +       struct gpio_chip chip;

> +       struct device *dev;

Wondering why you need this. Is it the same as chip.parent?

> +       struct regmap *regmap;
> +};

...

> +       int ret, bit;
> +
> +       bit = BIT(offset);

I prefer
  int bit = BIT(offset);
  int ret;
but I think we already discussed that. OK.

...

> +       default:
> +               break;
> +       }
> +       return -ENOTSUPP;

Here is a waste of line. Why break instead of direct return?

...

> +/* Template for GPIO chip */
> +static const struct gpio_chip bd71815gpo_chip = {
> +       .label                  = "bd71815",
> +       .owner                  = THIS_MODULE,
> +       .get                    = bd71815gpo_get,
> +       .get_direction          = bd71815gpo_direction_get,
> +       .set                    = bd71815gpo_set,
> +       .set_config             = bd71815_gpio_set_config,

> +       .can_sleep              = 1,

Strictly speaking this should be true (boolean type value).

> +};

...

> +#define BD71815_TWO_GPIOS      0x3UL
> +#define BD71815_ONE_GPIO       0x1UL

Are they masks? Can you use BIT() and GENMASK()?

...

> +/*
> + * Sigh. The BD71815 and BD71817 were originally designed to support two GPO
> + * pins. At some point it was noticed the second GPO pin which is the E5 pin
> + * located at the center of IC is hard to use on PCB (due to the location). It
> + * was decided to not promote this second GPO and pin is marked as GND in the

and the pin

> + * datasheet. The functionality is still there though! I guess driving a GPO
> + * connected to the ground is a bad idea. Thus we do not support it by default.
> + * OTOH - the original driver written by colleagues at Embest did support
> + * controlling this second GPO. It is thus possible this is used in some of the
> + * products.
> + *
> + * This driver does not by default support configuring this second GPO
> + * but allows using it by providing the DT property
> + * "rohm,enable-hidden-gpo".
> + */

...

> +       /*
> +        * As writing of this the sysfs interface for GPIO control does not
> +        * respect the valid_mask. Do not trust it but rather set the ngpios
> +        * to 1 if "rohm,enable-hidden-gpo" is not given.
> +        *
> +        * This check can be removed later if the sysfs export is fixed and
> +        * if the fix is backported.

So, mark this comment with the TODO/FIXME keyword?

> +        *
> +        * For now it is safest to just set the ngpios though.
> +        */

...

> +       ret = devm_gpiochip_add_data(dev, &g->chip, g);
> +       if (ret < 0) {
> +               dev_err(dev, "could not register gpiochip, %d\n", ret);
> +               return ret;
> +       }
> +
> +       return ret;

This entire piece can be simplified by

return devm_gpiochip_add_data(...);

...

> +static struct platform_driver gpo_bd71815_driver = {
> +       .driver = {
> +               .name   = "bd71815-gpo",

> +               .owner  = THIS_MODULE,

Seems I commented on this. The module_*_driver() macro(s) will take care of it.

> +       },
> +       .probe          = gpo_bd71815_probe,
> +};

> +

Extra blank line. Drop it.

> +module_platform_driver(gpo_bd71815_driver);

-- 
With Best Regards,
Andy Shevchenko