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From:   Bartosz Golaszewski <bgolaszewski@baylibre.com>
Date:   Fri, 25 Jun 2021 13:53:01 +0200
Message-ID: <CAMpxmJUvMTevyhkvq0YXg5d=G5qBzhi0mz0w0TjUuWCCvnnRCQ@mail.gmail.com>
Subject: Re: [PATCH] gpio: mt7621: support gpio-line-names property
To:     Sergio Paracuellos <sergio.paracuellos@gmail.com>
Cc:     linux-gpio <linux-gpio@vger.kernel.org>,
        Matthias Brugger <matthias.bgg@gmail.com>,
        Linus Walleij <linus.walleij@linaro.org>,
        git@johnthomson.fastmail.com.au,
        LKML <linux-kernel@vger.kernel.org>, neil@brown.name,
        =?UTF-8?Q?Ren=C3=A9_van_Dorst?= <opensource@vdorst.com>,
        Nicholas Mc Guire <hofrat@osadl.org>
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On Sat, Jun 19, 2021 at 9:35 AM Sergio Paracuellos
<sergio.paracuellos@gmail.com> wrote:
>
> 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-mt7621
> driver.
>
> This commit adds driver level support for the device tree
> property so that GPIO lines can be assigned friendly names.
>
> Signed-off-by: Sergio Paracuellos <sergio.paracuellos@gmail.com>
> ---
> Hi,
>
> This driver has three gpiochips with 32 gpios each. Core implmentation
> got gpio's repeated along each gpio chip if chip.names is not assigned.
> To avoid this behaviour driver will set this names as empty or
> with desired friendly line names. Consider the following sample with
> minimal entries for the first chip with this patch changes applied:
>
> &gpio {
>     gpio-line-names = "", "", "", "",
>                       "", "", "SFP LOS", "extcon port5 PoE compat",
>                       "SFP module def0", "LED blue SFP", "SFP tx disable", "",
>                       "switch USB power", "mode", "", "buzzer",
>                       "LED blue pwr", "switch port5 PoE out", "reset";
> };
>
> gpioinfo
> gpiochip0 - 32 lines:
>   line   0:      unnamed       unused  output  active-high
>   line   1:      unnamed       unused   input  active-high
>   line   2:      unnamed       unused   input  active-high
>   line   3:      unnamed       unused   input  active-high
>   line   4:      unnamed       unused   input  active-high
>   line   5:      unnamed       unused   input  active-high
>   line   6:    "SFP LOS"        "los"   input  active-high [used]
>   line   7: "extcon port5 PoE compat" unused input active-high
>   line   8: "SFP module def0" "mod-def0" input active-low [used]
>   line   9: "LED blue SFP" "blue:sfp" output active-high [used]
>   line  10: "SFP tx disable" "tx-disable" output active-high [used]
>   line  11:      unnamed       unused  output  active-high
>   line  12: "switch USB power" "usb_power" output active-high [used]
>   line  13:       "mode"       "mode"   input  active-high [used]
>   line  14:      unnamed       unused   input  active-high
>   line  15:     "buzzer"     "buzzer"  output  active-high [used]
>   line  16: "LED blue pwr" "blue:pwr" output active-high [used]
>   line  17: "switch port5 PoE out" "sysfs" input active-high [used]
>   line  18:      "reset"      "reset"   input  active-high [used]
>   line  19:      unnamed       unused   input  active-high
>   line  20:      unnamed       unused   input  active-high
>   line  21:      unnamed       unused   input  active-high
>   line  22:      unnamed       unused   input  active-high
>   line  23:      unnamed       unused   input  active-high
>   line  24:      unnamed       unused   input  active-high
>   line  25:      unnamed       unused   input  active-high
>   line  26:      unnamed       unused   input  active-high
>   line  27:      unnamed       unused   input  active-high
>   line  28:      unnamed       unused   input  active-high
>   line  29:      unnamed       unused   input  active-high
>   line  30:      unnamed       unused   input  active-high
>   line  31:      unnamed       unused   input  active-high
> gpiochip1 - 32 lines:
>   line   0:      unnamed       unused   input  active-high
>   line   1:      unnamed       unused   input  active-high
>   ...
>   line  31:      unnamed       unused   input  active-high
> gpiochip2 - 32 lines:
>   line   0:      unnamed       unused   input  active-high
>   line   1:      unnamed       unused   input  active-high
>   ...
>   line  31:      unnamed       unused   input  active-high
>
> To avoid gpiochip1 and gpiochip2 entries repeated with this
> minimal lines definition change, we assign empty reserved
> 'names' in driver code.
>
> Note that we also don't want to to prevent the driver from
> succeeding at probe due to an error in the gpio-line-names
> property and the ENODATA error is considered a valid result
> to terminate any further labeling so there is no need for
> an error message in that case. Other error results are
> unexpected so an error message indicating the consequence
> of the error is appropriate here.
>
> Thanks in advance for your time.
>
> Best regards,
>     Sergio Paracuellos
>
>  drivers/gpio/gpio-mt7621.c | 41 ++++++++++++++++++++++++++++++++++++++
>  1 file changed, 41 insertions(+)
>
> diff --git a/drivers/gpio/gpio-mt7621.c b/drivers/gpio/gpio-mt7621.c
> index 82fb20dca53a..b5f8fd8e928a 100644
> --- a/drivers/gpio/gpio-mt7621.c
> +++ b/drivers/gpio/gpio-mt7621.c
> @@ -206,6 +206,45 @@ mediatek_gpio_xlate(struct gpio_chip *chip,
>         return gpio % MTK_BANK_WIDTH;
>  }
>
> +static void
> +mediatek_gpio_set_names(struct device *dev, struct mtk_gc *rg)
> +{
> +       struct device_node *np = dev->of_node;
> +       const char **names;
> +       int nstrings, base;
> +       unsigned int i;
> +
> +       names = devm_kcalloc(dev, MTK_BANK_WIDTH, sizeof(*names),
> +                            GFP_KERNEL);
> +       if (!names)
> +               return;

While the ENODATA bit makes sense, not failing after an OOM in a
driver is wrong. Please return the error code here.

Bartosz

> +
> +       base = rg->bank * MTK_BANK_WIDTH;
> +       nstrings = of_property_count_strings(np, "gpio-line-names");
> +       if (nstrings <= base)
> +               goto assign_names;
> +
> +       for (i = 0; i < MTK_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;
> +               }
> +
> +               if (*name)
> +                       names[i] = name;
> +       }
> +
> +assign_names:
> +       rg->chip.names = names;
> +}
> +
>  static int
>  mediatek_gpio_bank_probe(struct device *dev,
>                          struct device_node *node, int bank)
> @@ -241,6 +280,8 @@ mediatek_gpio_bank_probe(struct device *dev,
>         if (!rg->chip.label)
>                 return -ENOMEM;
>
> +       mediatek_gpio_set_names(dev, rg);
> +
>         rg->irq_chip.name = dev_name(dev);
>         rg->irq_chip.parent_device = dev;
>         rg->irq_chip.irq_unmask = mediatek_gpio_irq_unmask;
> --
> 2.25.1
>