linux-kernel - Re: [PATCH v5 05/12] gpio: aggregator: refactor the code to add GPIO desc in the forwarder

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Message-ID: <CAMuHMdXjc8hV4mvq0oOZDERajei+-sGxevq9m1wfQ=VCvod-6Q@mail.gmail.com>
Date: Fri, 9 May 2025 10:43:51 +0200
From: Geert Uytterhoeven <geert@...ux-m68k.org>
To: Thomas Richard <thomas.richard@...tlin.com>
Cc: Linus Walleij <linus.walleij@...aro.org>, 
	Andy Shevchenko <andriy.shevchenko@...ux.intel.com>, Bartosz Golaszewski <brgl@...ev.pl>, 
	Kees Cook <kees@...nel.org>, Andy Shevchenko <andy@...nel.org>, linux-gpio@...r.kernel.org, 
	linux-kernel@...r.kernel.org, thomas.petazzoni@...tlin.com, 
	DanieleCleri@...on.eu, GaryWang@...on.com.tw, linux-hardening@...r.kernel.org
Subject: Re: [PATCH v5 05/12] gpio: aggregator: refactor the code to add GPIO
 desc in the forwarder

On Fri, 9 May 2025 at 10:38, Geert Uytterhoeven <geert@...ux-m68k.org> wrote:
> On Tue, 6 May 2025 at 17:21, Thomas Richard <thomas.richard@...tlin.com> wrote:
> > Create a dedicated function to add a GPIO desc in the forwarder. Instead of
> > passing an array of GPIO descs, now the GPIO descs are passed on by one to
>
> one by one
>
> > the forwarder.
>
> Also, the passed array is no longer stored as-is, but copied.
>
> >
> > Signed-off-by: Thomas Richard <thomas.richard@...tlin.com>

> >  /**
> >   * gpiochip_fwd_create() - Create a new GPIO forwarder
> >   * @dev: Parent device pointer

      * @ngpios: Number of GPIOs in the forwarder.
      * @descs: Array containing the GPIO descriptors to forward to.
      *         This array must contain @ngpios entries, and must not
be deallocated
      *         before the forwarder has been destroyed again.

This needs an update, as the array is copied.

> > @@ -559,26 +593,12 @@ static struct gpiochip_fwd *gpiochip_fwd_create(struct device *dev,
> >
> >         chip = &fwd->chip;
> >
> > -       /*
> > -        * If any of the GPIO lines are sleeping, then the entire forwarder
> > -        * will be sleeping.
> > -        * If any of the chips support .set_config(), then the forwarder will
> > -        * support setting configs.
> > -        */
> >         for (i = 0; i < ngpios; i++) {
> > -               struct gpio_chip *parent = gpiod_to_chip(descs[i]);
> > -
> > -               dev_dbg(dev, "%u => gpio %d irq %d\n", i,
> > -                       desc_to_gpio(descs[i]), gpiod_to_irq(descs[i]));
> > -
> > -               if (gpiod_cansleep(descs[i]))
> > -                       chip->can_sleep = true;
> > -               if (parent && parent->set_config)
> > -                       chip->set_config = gpio_fwd_set_config;
> > +               error = gpiochip_fwd_gpio_add(fwd, descs[i], i);
> > +               if (error)
> > +                       return ERR_PTR(error);
> >         }
> >
> > -       fwd->descs = descs;
>
> So the passed array is no longer stored, and thus the caller
> (gpio_aggregator_probe()) can free it after the call.
>
> > -
> >         if (chip->can_sleep)
> >                 mutex_init(&fwd->mlock);
> >         else

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds