linux-kernel - Re: [PATCH v4 2/2] gpiolib: check the 'ngpios' property in core gpiolib code

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Message-ID: <CAMRc=MfBvFzww_wZ=afjUY4aSnyKyL2ZXLmfWbu_u3tnZ8J0Ng@mail.gmail.com>
Date:   Mon, 6 Dec 2021 16:01:25 +0100
From:   Bartosz Golaszewski <brgl@...ev.pl>
To:     Linus Walleij <linus.walleij@...aro.org>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Johan Hovold <johan@...nel.org>
Cc:     "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4 2/2] gpiolib: check the 'ngpios' property in core
 gpiolib code

On Thu, Dec 2, 2021 at 2:40 PM Bartosz Golaszewski <brgl@...ev.pl> wrote:
>
> Several drivers read the 'ngpios' device property on their own, but
> since it's defined as a standard GPIO property in the device tree bindings
> anyway, it's a good candidate for generalization. If the driver didn't
> set its gc->ngpio, try to read the 'ngpios' property from the GPIO
> device's firmware node before bailing out.
>
> Signed-off-by: Bartosz Golaszewski <brgl@...ev.pl>
> Suggested-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
> Reviewed-by: Linus Walleij <linus.walleij@...aro.org>
> ---
> v1 -> v2:
> - use device_property_read_u32() instead of fwnode_property_read_u32()
> - reverse the error check logic
>
> v2 -> v3:
> - don't shadow errors other than -ENODATA in device_property_read_u32()
>
> v3 -> v4:
> - also make sure we return -EINVAL when the device 'ngpios' property is
>   set to 0 (thanks Andy!)
>
>  drivers/gpio/gpiolib.c | 21 +++++++++++++++++++++
>  1 file changed, 21 insertions(+)
>
> diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
> index ede8b8a7aa18..bd9b8cb53476 100644
> --- a/drivers/gpio/gpiolib.c
> +++ b/drivers/gpio/gpiolib.c
> @@ -599,6 +599,7 @@ int gpiochip_add_data_with_key(struct gpio_chip *gc, void *data,
>         int base = gc->base;
>         unsigned int i;
>         int ret = 0;
> +       u32 ngpios;
>
>         /*
>          * First: allocate and populate the internal stat container, and
> @@ -646,6 +647,26 @@ int gpiochip_add_data_with_key(struct gpio_chip *gc, void *data,
>                 goto err_free_dev_name;
>         }
>
> +       /*
> +        * Try the device properties if the driver didn't supply the number
> +        * of GPIO lines.
> +        */
> +       if (gc->ngpio == 0) {
> +               ret = device_property_read_u32(&gdev->dev, "ngpios", &ngpios);
> +               if (ret == -ENODATA)
> +                       /*
> +                        * -ENODATA means that there is no property found and
> +                        * we want to issue the error message to the user.
> +                        * Besides that, we want to return different error code
> +                        * to state that supplied value is not valid.
> +                        * */
> +                       ngpios = 0;
> +               else if (ret)
> +                       goto err_free_descs;
> +
> +               gc->ngpio = ngpios;
> +       }
> +
>         if (gc->ngpio == 0) {
>                 chip_err(gc, "tried to insert a GPIO chip with zero lines\n");
>                 ret = -EINVAL;
> --
> 2.25.1
>

Queued for next.

Bart