From: Bartosz Golaszewski <brgl@bgdev.pl>
To: Andy Shevchenko <andy.shevchenko@gmail.com>
Cc: Linus Walleij <linus.walleij@linaro.org>,
Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
"open list:GPIO SUBSYSTEM" <linux-gpio@vger.kernel.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] gpiolib: fix the size of the ngpios variable
Date: Sun, 6 Mar 2022 20:22:16 +0100 [thread overview]
Message-ID: <CAMRc=Md011QRB1z0h=ktYwxKJbH1EQhvZWLnNzU1bhpXuo9sqA@mail.gmail.com> (raw)
In-Reply-To: <CAHp75VefVkNfGoFKtG3-3fF4TEiu33u-EaASEiTUmj_OAm-onA@mail.gmail.com>
On Sat, Mar 5, 2022 at 10:27 PM Andy Shevchenko
<andy.shevchenko@gmail.com> wrote:
>
> On Sat, Mar 5, 2022 at 10:14 PM Bartosz Golaszewski <brgl@bgdev.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.
>
Ah right. It's not very obvious from the docs but the DT syntax must
be different for 16 bits. In that case our best shot is to read a
32-bit unsigned integer and check if its value doesn't exceed
UINT16_MAX.
Bart
prev parent reply other threads:[~2022-03-06 19:22 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-03-05 15:42 [PATCH] gpiolib: fix the size of the ngpios variable Bartosz Golaszewski
2022-03-05 21:26 ` Andy Shevchenko
2022-03-06 19:22 ` Bartosz Golaszewski [this message]
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