Re: [PATCH] gpiolib: use __counted_by() for GPIO descriptors

[Bartosz Golaszewski <brgl@xxxxxxxx>]

On Tue, Dec 19, 2023 at 4:12 PM Andy Shevchenko
<andriy.shevchenko@xxxxxxxxxxxxxxx> wrote:
>
> On Tue, Dec 19, 2023 at 01:57:06PM +0100, Bartosz Golaszewski wrote:
> > From: Bartosz Golaszewski <bartosz.golaszewski@xxxxxxxxxx>
> >
> > Pull the array of GPIO descriptors into struct gpio_device as a flexible
> > array and use __counted_by() to control its size.
>
> How big is the struct gpio_device? Unifying like this might provoke subtle
> errors on very fragmented memory, where k*alloc() might not find enough free
> space. Note, k*alloc() guarantees finding only memory for a single page.
> With PAGE_SIZE = 4k, this might be an issue.
>
> I would suggest, if nothing prevents us from switching, to use kvmalloc().
>

That's a good point but there's another thing. We need to call
gpiochip_get_ngpios() before the allocation. I need to revisit this
one.

Bart

> --
> With Best Regards,
> Andy Shevchenko
>
>