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

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Message-ID: <ZPWcTMPiu4MSq+F7@smile.fi.intel.com>
Date:   Mon, 4 Sep 2023 11:58:52 +0300
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     Bartosz Golaszewski <brgl@...ev.pl>
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] gpio: sim: don't fiddle with GPIOLIB private members

On Sat, Sep 02, 2023 at 04:40:05PM +0200, Bartosz Golaszewski wrote:
> On Fri, Sep 1, 2023 at 11:10 PM Andy Shevchenko
> <andriy.shevchenko@...ux.intel.com> wrote:
> > On Fri, Sep 01, 2023 at 08:32:40PM +0200, Bartosz Golaszewski wrote:

...

> > > -static void gpio_sim_free(struct gpio_chip *gc, unsigned int offset)
> >
> > Why is this?
> 
> Dunno, some git shenanigans?

Time to use --patience then?

...

> > > -     /* Used by sysfs and configfs callbacks. */
> > > -     dev_set_drvdata(&gc->gpiodev->dev, chip);
> > > +     /* Used by sysfs callbacks. */
> > > +     dev_set_drvdata(swnode->dev, chip);
> >
> > dev pointer of firmware node is solely for dev links. Is it the case here?
> > Seems to me you luckily abuse it.
> 
> I don't think so. If anything we have a helper in the form of
> get_dev_from_fwnode() but it takes reference to the device while we
> don't need it - we know it'll be there because we created it.
> 
> This information (struct device of the GPIO device) can also be
> retrieved by iterating over the device children of the top platform
> device and comparing their fwnodes against the one we got passed down
> from probe() but it's just so many extra steps.
> 
> Or we can have a getter in gpio/driver.h for that but I don't want to
> expose another interface is we can simply use the fwnode.

dev pointer in the fwnode strictly speaking is optional. No-one, except
its solely user, should rely on it (its presence and lifetime).

-- 
With Best Regards,
Andy Shevchenko