From: Rosen Penev <rosenp@gmail.com>
To: Bartosz Golaszewski <brgl@kernel.org>
Cc: Kees Cook <kees@kernel.org>,
linux-gpio@vger.kernel.org,
Bamvor Jian Zhang <bamv2005@gmail.com>,
Linus Walleij <linusw@kernel.org>,
"Gustavo A. R. Silva" <gustavoars@kernel.org>,
open list <linux-kernel@vger.kernel.org>,
"open list:KERNEL HARDENING (not covered by other
areas):Keyword:b__counted_by(_le|_be)?b"
<linux-hardening@vger.kernel.org>
Subject: Re: [PATCH] gpio: mockup: allocate lines with main struct
Date: Tue, 24 Mar 2026 08:51:56 -0700 [thread overview]
Message-ID: <CAKxU2N8gudRXR-bLMoyDVDuv3vWuzqrbyVsHL=Gu3mDZWMvs6w@mail.gmail.com> (raw)
In-Reply-To: <CAMRc=Me2RLj-vvCVNho9CPYVwsQHypC_KvKHJWkLyj=rMkfx2w@mail.gmail.com>
On Tue, Mar 24, 2026 at 2:16 AM Bartosz Golaszewski <brgl@kernel.org> wrote:
>
> On Mon, 23 Mar 2026 17:43:00 +0100, Rosen Penev <rosenp@gmail.com> said:
> > On Mon, Mar 23, 2026 at 3:00 AM Bartosz Golaszewski <brgl@kernel.org> wrote:
> >>
> >> On Sat, Mar 21, 2026 at 12:00 AM Rosen Penev <rosenp@gmail.com> wrote:
> >> >
> >> > >
> >> > > static int gpio_mockup_probe(struct platform_device *pdev)
> >> > > {
> >> > > ...
> >> > > u16 ngpio;
> >> > > ...
> >> > > rv = device_property_read_u16(dev, "nr-gpios", &ngpio);
> >> > > ...
> >> > > gc->ngpio = ngpio;
> >> > > ...
> >> > > chip->lines = devm_kcalloc(dev, gc->ngpio,
> >> > > sizeof(*chip->lines), GFP_KERNEL);
> >> > >
> >> > > But this begs the question: why add nr_lines when ngpio is already part
> >> > > of the struct:
> >> > Maintainers for some inexplicable reason want an extra variable for
> >> > __counted_by works.
> >>
> >> I believe what Kees means here is: you can use ngpio for __counted_by() like so:
> >>
> >> __counted_by(gc.ngpio)
> > __counted_by doesn't support nested variables like that.
> >
> > drivers/gpio/gpio-mockup.c:59:61: error: ‘gc’ undeclared here (not in
> > a function)
> > 59 | struct gpio_mockup_line_status lines[] __counted_by(gc.ngpio);
>
> The following spin on your patch builds fine for me:
>
> diff --git a/drivers/gpio/gpio-mockup.c b/drivers/gpio/gpio-mockup.c
> index a7d69f3835c1e..9427ab8c45f73 100644
> --- a/drivers/gpio/gpio-mockup.c
> +++ b/drivers/gpio/gpio-mockup.c
> @@ -52,10 +52,10 @@ struct gpio_mockup_line_status {
>
> struct gpio_mockup_chip {
> struct gpio_chip gc;
> - struct gpio_mockup_line_status *lines;
> struct irq_domain *irq_sim_domain;
> struct dentry *dbg_dir;
> struct mutex lock;
> + struct gpio_mockup_line_status lines[] __counted_by(gc.ngpio);
You're using an older compiler. This does not work at all.
* Optional: only supported since gcc >= 15
* Optional: only supported since clang >= 18
> };
>
> struct gpio_mockup_dbgfs_private {
> @@ -436,15 +436,16 @@ static int gpio_mockup_probe(struct platform_device *pdev)
> if (rv)
> name = dev_name(dev);
>
> - chip = devm_kzalloc(dev, sizeof(*chip), GFP_KERNEL);
> + chip = devm_kzalloc(dev, struct_size(chip, lines, ngpio), GFP_KERNEL);
> if (!chip)
> return -ENOMEM;
>
> - mutex_init(&chip->lock);
> -
> gc = &chip->gc;
> - gc->base = base;
> gc->ngpio = ngpio;
> + gc->base = base;
> +
> + mutex_init(&chip->lock);
> +
> gc->label = name;
> gc->owner = THIS_MODULE;
> gc->parent = dev;
> @@ -460,11 +461,6 @@ static int gpio_mockup_probe(struct platform_device *pdev)
> gc->request = gpio_mockup_request;
> gc->free = gpio_mockup_free;
>
> - chip->lines = devm_kcalloc(dev, gc->ngpio,
> - sizeof(*chip->lines), GFP_KERNEL);
> - if (!chip->lines)
> - return -ENOMEM;
> -
> for (i = 0; i < gc->ngpio; i++)
> chip->lines[i].dir = GPIO_LINE_DIRECTION_IN;
>
> Bart
next prev parent reply other threads:[~2026-03-24 15:52 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-03-19 0:05 [PATCH] gpio: mockup: allocate lines with main struct Rosen Penev
2026-03-20 13:28 ` Linus Walleij
2026-03-20 18:10 ` Kees Cook
2026-03-20 23:00 ` Rosen Penev
2026-03-23 10:00 ` Bartosz Golaszewski
2026-03-23 16:43 ` Rosen Penev
2026-03-24 9:16 ` Bartosz Golaszewski
2026-03-24 15:51 ` Rosen Penev [this message]
2026-03-24 15:54 ` Bartosz Golaszewski
2026-03-24 15:56 ` Rosen Penev
2026-03-24 17:16 ` Bartosz Golaszewski
2026-03-24 18:25 ` Rosen Penev
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