linux-kernel - Re: [PATCH v2 3/4] gpio: aggregator: Set up a parser of delay line parameters

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Date:   Thu, 15 Jun 2023 09:48:27 +0200
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc:     Bartosz Golaszewski <bartosz.golaszewski@...aro.org>,
        Alexander Stein <alexander.stein@...tq-group.com>,
        linux-kernel@...r.kernel.org, linux-gpio@...r.kernel.org,
        Linus Walleij <linus.walleij@...aro.org>,
        Bartosz Golaszewski <brgl@...ev.pl>,
        Andy Shevchenko <andy@...nel.org>
Subject: Re: [PATCH v2 3/4] gpio: aggregator: Set up a parser of delay line parameters

Hi Andy,

On Thu, Jun 15, 2023 at 1:14 AM Andy Shevchenko
<andriy.shevchenko@...ux.intel.com> wrote:
> The aggregator mode can also handle properties of the platform,
> that do not belong to the GPIO controller itself. One of such
> a property is a signal delay line. Set up a parser to support it.
>
> Signed-off-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>

Thanks for your patch!

Reviewed-by: Geert Uytterhoeven <geert+renesas@...der.be>

One suggestion for improvement below...

> --- a/drivers/gpio/gpio-aggregator.c
> +++ b/drivers/gpio/gpio-aggregator.c
> @@ -525,7 +580,9 @@ static int gpio_aggregator_probe(struct platform_device *pdev)
>                         return PTR_ERR(descs[i]);
>         }
>
> -       fwd = gpiochip_fwd_create(dev, n, descs);
> +       delay_line = fwnode_device_is_compatible(dev_fwnode(dev), "gpio-delay");

Please do not use explicit checks for compatible values in .probe()
methods.  Instead, use device_get_match_data() to get the feature
flag(s).  This will also make it easier to scale to other external
components later.

> +
> +       fwd = gpiochip_fwd_create(dev, n, descs, delay_line);
>         if (IS_ERR(fwd))
>                 return PTR_ERR(fwd);
>
> @@ -534,6 +591,15 @@ static int gpio_aggregator_probe(struct platform_device *pdev)
>  }
>
>  static const struct of_device_id gpio_aggregator_dt_ids[] = {
> +       /*
> +        * The GPIO delay provides a way to configure platform specific delays
> +        * for GPIO ramp-up or ramp-down delays. This can serve the following
> +        * purposes:
> +        * - Open-drain output using an RC filter
> +        */
> +       {
> +               .compatible = "gpio-delay",

.data = (void *)FWD_FEATURE_DELAY,

> +       },
>         /*
>          * Add GPIO-operated devices controlled from userspace below,
>          * or use "driver_override" in sysfs.

Gr{oetje,eeting}s,

                        Geert


--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds