linux-kernel - Re: [rft, PATCH v3 1/1] gpiolib: Get rid of not used of

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Message-ID: <Y3T2HolVIeHQR8Kz@smile.fi.intel.com>
Date:   Wed, 16 Nov 2022 16:39:26 +0200
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     Thierry Reding <treding@...dia.com>
Cc:     Dmitry Torokhov <dmitry.torokhov@...il.com>,
        Bartosz Golaszewski <bartosz.golaszewski@...aro.org>,
        Linus Walleij <linus.walleij@...aro.org>,
        linux-gpio@...r.kernel.org, linux-acpi@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Mika Westerberg <mika.westerberg@...ux.intel.com>,
        Bartosz Golaszewski <brgl@...ev.pl>
Subject: Re: [rft, PATCH v3 1/1] gpiolib: Get rid of not used of_node member

On Wed, Nov 16, 2022 at 04:09:44PM +0200, Andy Shevchenko wrote:
> On Wed, Nov 16, 2022 at 02:47:07PM +0100, Thierry Reding wrote:
> > On Wed, Nov 16, 2022 at 11:18:59AM +0200, Andy Shevchenko wrote:

...

> > > +	/* If the calling driver did not initialize firmware node, do it here */
> > >  	if (gc->fwnode)
> > >  		fwnode = gc->fwnode;
> > >  	else if (gc->parent)
> > >  		fwnode = dev_fwnode(gc->parent);
> > > +	gc->fwnode = fwnode;
> > 
> > I'm not sure we want to set this one. We recently discussed this in
> > another thread and my reading is that gc->fwnode is supposed to be used
> > only to explicitly override which fwnode to use if the default isn't
> > appropriate. Right now the standard way to access the device's fwnode
> > seems to be dev_fwnode(&gdev->dev), with only very few exceptions, so
> > it'd be great if we could settle on that, rather than introduce a second
> > field that contains the same value and use them interchangeably.
> > 
> > One way we could enforce this is by setting gc->fwnode to NULL here
> > instead of fwnode. That should cause a crash anywhere it's used after
> > this, so we should be able to easily weed out any abuses.
> > 
> > Of course if people prefer to use gc->fwnode instead, then we may want
> > to remove all uses of gdev->dev.fwnode. There's simply no point in
> > keeping the same value in two different place, it's just going to lead
> > to a big mess.
> 
> I prefer that we explicitly use GPIO device firmware node.
> Independently on this message I came up with another patch
> (I'm just about to sent it right away) which I think it
> the best to have in current case.
> 
> Ideally I would like to see const struct gpio_chip *gc to be a parameter
> to the GPIO chip add(). But it may happen in distant future.

I have updated this patch locally to use dev_of_node() instead of
to_of_node(chip->fwnode), and also relying on the patch I just sent.

Nevertheless, for of_gpiochip_add()/of_gpiochip_remove() and
of_mm_gpiochip_add_data() I still left use of fwnode, because it feels
the right thing to do: we are taking reference on the input data in
such cases.

-- 
With Best Regards,
Andy Shevchenko