linux-kernel - Re: [PATCH v3] gpio: sim: don't fiddle with GPIOLIB private members

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Message-ID: <CAMRc=Mc1K-xMzbtLSvZcSuXpLPmGkHekonjx5m_519OuxOxuxA@mail.gmail.com>
Date:   Tue, 5 Sep 2023 14:09:15 +0200
From:   Bartosz Golaszewski <brgl@...ev.pl>
To:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc:     Linus Walleij <linus.walleij@...aro.org>,
        Kent Gibson <warthog618@...il.com>, linux-gpio@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
Subject: Re: [PATCH v3] gpio: sim: don't fiddle with GPIOLIB private members

On Tue, Sep 5, 2023 at 2:05 PM Andy Shevchenko
<andriy.shevchenko@...ux.intel.com> wrote:
>
> On Tue, Sep 05, 2023 at 10:24:13AM +0200, Bartosz Golaszewski wrote:
> > From: Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
> >
> > We access internals of struct gpio_device and struct gpio_desc because
> > it's easier but it can actually be avoided and we're working towards a
> > better encapsulation of GPIO data structures across the kernel so let's
> > start at home.
> >
> > Instead of checking gpio_desc flags, let's just track the requests of
> > GPIOs in the driver. We also already store the information about
> > direction of simulated lines.
> >
> > For kobjects needed by sysfs callbacks: we can iterate over the children
> > devices of the top-level platform device and compare their fwnodes
> > against the one passed to the init function from probe.
> >
> > While at it: fix one line break and remove the untrue part about
> > configfs callbacks using dev_get_drvdata() from a comment.
>
> ...
>
> > v2 -> v3:
> > - don't use fwnode internal fields, instead: iterate over the platform
> >   device's children and locate the GPIO device
>
> Thank you!
>
> ...
>
> > @@ -181,7 +178,7 @@ static int gpio_sim_get_direction(struct gpio_chip *gc, unsigned int offset)
>
> >  static int gpio_sim_set_config(struct gpio_chip *gc,
> > -                               unsigned int offset, unsigned long config)
> > +                            unsigned int offset, unsigned long config)
>
> Looking at other prototypes, it can be
>
> static int gpio_sim_set_config(struct gpio_chip *gc, unsigned int offset,
>                                unsigned long config)
>
> ...
>
> > +static int gpio_sim_chip_set_device(struct device *dev, void *data)
> > +{
> > +     struct gpio_sim_chip *chip = data;
>
> > +     if (chip->swnode == dev->fwnode) {
>
> Please do not dereference fwnode from the struct device, we have an API!
> device_match_fwnode()
>
> > +             chip->dev = dev;
> > +             return 1;
> > +     }
> > +
> > +     return 0;
> > +}
>
> ...
>
> > +     chip->swnode = swnode;
> > +     ret = device_for_each_child(dev, chip, gpio_sim_chip_set_device);
> > +     if (!ret)
> > +             return -ENODEV;
>
> Can bus_find_device_by_fwnode() be used here?
>

I can but then we're iterating over all platform devices and not just
children of this GPIO simulator. If you think it's better for even
less fwnode juggling then I can go with it.

Bart

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