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From: Bartosz Golaszewski <brgl@bgdev.pl>
Date: Wed, 20 Dec 2023 09:16:17 +0100
Message-ID: <CAMRc=McFsswSjCU5m+_wmmxQh+T1DkwnrBsYp_KsQfOSwENvLw@mail.gmail.com>
Subject: Re: [PATCH] gpiolib: use __counted_by() for GPIO descriptors
To: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: Linus Walleij <linus.walleij@linaro.org>, Kent Gibson <warthog618@gmail.com>, 
	linux-gpio@vger.kernel.org, linux-kernel@vger.kernel.org, 
	Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
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On Tue, Dec 19, 2023 at 4:12=E2=80=AFPM Andy Shevchenko
<andriy.shevchenko@linux.intel.com> wrote:
>
> On Tue, Dec 19, 2023 at 01:57:06PM +0100, Bartosz Golaszewski wrote:
> > From: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
> >
> > Pull the array of GPIO descriptors into struct gpio_device as a flexibl=
e
> > array and use __counted_by() to control its size.
>
> How big is the struct gpio_device? Unifying like this might provoke subtl=
e
> errors on very fragmented memory, where k*alloc() might not find enough f=
ree
> space. Note, k*alloc() guarantees finding only memory for a single page.
> With PAGE_SIZE =3D 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
>
>