linux-kernel - Re: [PATCH] gpiolib: fix the size of the ngpios variable

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Message-ID: <CAHp75VefVkNfGoFKtG3-3fF4TEiu33u-EaASEiTUmj_OAm-onA@mail.gmail.com>
Date:   Sat, 5 Mar 2022 23:26:55 +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] gpiolib: fix the size of the ngpios variable

On Sat, Mar 5, 2022 at 10:14 PM Bartosz Golaszewski <brgl@...ev.pl> wrote:
>
> The ngpio fields both in struct gpio_device as well as gpio_chip are
> 16 bit unsigned integers. Let's not risk an overflow and use the correct
> size when reading the device property.

...

> -               ret = device_property_read_u32(&gdev->dev, "ngpios", &ngpios);
> +               ret = device_property_read_u16(&gdev->dev, "ngpios", &ngpios);

AFAIU DT format you may not do this. The property is ABI-like and it's
32-bit (BE!). Reading as u16 will bring you 2 MSB (bytes) out of 4
from the 32-bit value.

-- 
With Best Regards,
Andy Shevchenko