linux-kernel - Re: [PATCH V2] gpio: brcmstb: support gpio-line-names property

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Message-ID: <CAMpxmJXNQQTxRWZSP0RZTUuefAk3+AeDMVeVkgERy7f9X=CBsA@mail.gmail.com>
Date:   Wed, 11 Mar 2020 13:44:56 +0100
From:   Bartosz Golaszewski <bgolaszewski@...libre.com>
To:     Doug Berger <opendmb@...il.com>
Cc:     Gregory Fong <gregory.0xf0@...il.com>,
        Linus Walleij <linus.walleij@...aro.org>,
        Florian Fainelli <f.fainelli@...il.com>,
        bcm-kernel-feedback-list@...adcom.com,
        linux-gpio <linux-gpio@...r.kernel.org>,
        arm-soc <linux-arm-kernel@...ts.infradead.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH V2] gpio: brcmstb: support gpio-line-names property

pon., 9 mar 2020 o 20:02 Doug Berger <opendmb@...il.com> napisał(a):
>
> The default handling of the gpio-line-names property by the
> gpiolib-of implementation does not work with the multiple
> gpiochip banks per device structure used by the gpio-brcmstb
> driver.
>
> This commit adds driver level support for the device tree
> property so that GPIO lines can be assigned friendly names.
>
> Signed-off-by: Doug Berger <opendmb@...il.com>
> ---
>  drivers/gpio/gpio-brcmstb.c | 44 ++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 44 insertions(+)
>
> diff --git a/drivers/gpio/gpio-brcmstb.c b/drivers/gpio/gpio-brcmstb.c
> index 05e3f99ae59c..fcfc1a1f1a5c 100644
> --- a/drivers/gpio/gpio-brcmstb.c
> +++ b/drivers/gpio/gpio-brcmstb.c
> @@ -603,6 +603,49 @@ static const struct dev_pm_ops brcmstb_gpio_pm_ops = {
>         .resume_noirq = brcmstb_gpio_resume,
>  };
>
> +static void brcmstb_gpio_set_names(struct device *dev,
> +                                  struct brcmstb_gpio_bank *bank)
> +{
> +       struct device_node *np = dev->of_node;
> +       const char **names;
> +       int nstrings, base;
> +       unsigned int i;
> +
> +       base = bank->id * MAX_GPIO_PER_BANK;
> +
> +       nstrings = of_property_count_strings(np, "gpio-line-names");
> +       if (nstrings <= base)
> +               /* Line names not present */
> +               return;
> +
> +       names = devm_kcalloc(dev, MAX_GPIO_PER_BANK, sizeof(*names),
> +                            GFP_KERNEL);
> +       if (!names)
> +               return;
> +
> +       /*
> +        * Make sure to not index beyond the end of the number of descriptors
> +        * of the GPIO device.
> +        */
> +       for (i = 0; i < bank->width; i++) {
> +               const char *name;
> +               int ret;
> +
> +               ret = of_property_read_string_index(np, "gpio-line-names",
> +                                                   base + i, &name);
> +               if (ret) {
> +                       if (ret != -ENODATA)
> +                               dev_err(dev, "unable to name line %d: %d\n",
> +                                       base + i, ret);
> +                       break;
> +               }

This bit is confusing to me. If we can't read the property we break
the loop and leave the remaining line names null but at the same time
it isn't considered a probe failure? Would you mind at least
commenting on this in the code?

Bart

> +               if (*name)
> +                       names[i] = name;
> +       }
> +
> +       bank->gc.names = names;
> +}
> +
>  static int brcmstb_gpio_probe(struct platform_device *pdev)
>  {
>         struct device *dev = &pdev->dev;
> @@ -726,6 +769,7 @@ static int brcmstb_gpio_probe(struct platform_device *pdev)
>                 need_wakeup_event |= !!__brcmstb_gpio_get_active_irqs(bank);
>                 gc->write_reg(reg_base + GIO_MASK(bank->id), 0);
>
> +               brcmstb_gpio_set_names(dev, bank);
>                 err = gpiochip_add_data(gc, bank);
>                 if (err) {
>                         dev_err(dev, "Could not add gpiochip for bank %d\n",
> --
> 2.7.4
>