linux-kernel - Re: [PATCH v2 07/11] gpiolib: replace find_chip_by_name() with gpio_device_find_by

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Message-ID: <CAMRc=MdBEm71uVYwRYiLvi2ROTDH5O5exa9Nq5qQc=yQOiXpew@mail.gmail.com>
Date:   Tue, 12 Sep 2023 13:34:46 +0200
From:   Bartosz Golaszewski <brgl@...ev.pl>
To:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc:     Linus Walleij <linus.walleij@...aro.org>,
        Mika Westerberg <mika.westerberg@...ux.intel.com>,
        linux-gpio@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-acpi@...r.kernel.org,
        Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
Subject: Re: [PATCH v2 07/11] gpiolib: replace find_chip_by_name() with gpio_device_find_by_label()

On Tue, Sep 12, 2023 at 1:08 PM Andy Shevchenko
<andriy.shevchenko@...ux.intel.com> wrote:
>
> On Tue, Sep 12, 2023 at 12:07:23PM +0200, Bartosz Golaszewski wrote:
> > From: Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
> >
> > Remove all remaining uses of find_chip_by_name() (and subsequently:
> > gpiochip_find()) from gpiolib.c and use the new
> > gpio_device_find_by_label() instead.
>
> ...
>
> >       for (hog = &hogs[0]; hog->chip_label; hog++) {
> > +             struct gpio_device *gdev __free(gpio_device_put) = NULL;
>
> In the loop?! How does it work when loop goes second iteration and so on?
>

This works fine, the variable goes out of scope (reference is put) on
every iteration.

Bart

> >               list_add_tail(&hog->list, &gpio_machine_hogs);
> >
> >               /*
> >                * The chip may have been registered earlier, so check if it
> >                * exists and, if so, try to hog the line now.
> >                */
> > -             gc = find_chip_by_name(hog->chip_label);
> > -             if (gc)
> > -                     gpiochip_machine_hog(gc, hog);
> > +             gdev = gpio_device_find_by_label(hog->chip_label);
> > +             if (gdev)
> > +                     gpiochip_machine_hog(gpio_device_get_chip(gdev), hog);
>
> So, do we expect the chip_label be different between hogs? Ah, seems so
> as it covers _all_ hogs in the system.
>
> >       }
>
> Even if the __free() scope works fine, I think this algorithm should be
> revisited to make sure we have iterating only on hogs of the same chip.
> Hence, the hogs should be placed into tree structure with a label being
> the key in it.
>
> ...
>
> > +             struct gpio_device *gdev __free(gpio_device_put) = NULL;
>
> > +             gc = gpio_device_get_chip(gdev);
>
> Similar wish here, perhaps maple tree can be utilized in the future for both of them.
>
> --
> With Best Regards,
> Andy Shevchenko
>
>