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

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Date:   Thu, 11 Nov 2021 22:47:06 +0200
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Bartosz Golaszewski <brgl@...ev.pl>
Cc:     Linus Walleij <linus.walleij@...aro.org>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH RFC 2/2] gpiolib: check the 'ngpios' property in core
 gpiolib code

On Thu, Nov 11, 2021 at 10:26 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.

Thanks!

...

> +               ret = fwnode_property_read_u32(gdev->dev.fwnode, "ngpios",
> +                                              &ngpios);

I'm wondering if there is any obstacle to call

               ret = device_property_read_u32(&gdev->dev, "ngpios", &ngpios);

?

Rationale (the main one) is to avoid direct dereference of fwnode from
struct device (it might be changed in the future). I really prefer API
calls here.

> +               if (ret == 0) {
> +                       gc->ngpio = ngpios;
> +               } else {
> +                       chip_err(gc, "tried to insert a GPIO chip with zero lines\n");
> +                       ret = -EINVAL;
> +                       goto err_free_descs;
> +               }

I would prefer the other way around and without 'else' being involved.

>         }


-- 
With Best Regards,
Andy Shevchenko