linux-kernel - Re: [PATCH v6 8/8] reset: gpio: use software nodes to setup the GPIO lookup

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Message-ID: <CAMRc=MfsyZ3wqMSQ9jcTFHp2RUrZ=Ge1xdPY44VAGqJ9_XD7QA@mail.gmail.com>
Date: Wed, 19 Nov 2025 00:28:26 -0800
From: Bartosz Golaszewski <brgl@...ev.pl>
To: Philipp Zabel <p.zabel@...gutronix.de>
Cc: Linus Walleij <linus.walleij@...aro.org>, 
	Andy Shevchenko <andriy.shevchenko@...ux.intel.com>, Daniel Scally <djrscally@...il.com>, 
	Heikki Krogerus <heikki.krogerus@...ux.intel.com>, 
	Sakari Ailus <sakari.ailus@...ux.intel.com>, 
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>, "Rafael J. Wysocki" <rafael@...nel.org>, 
	Danilo Krummrich <dakr@...nel.org>, Krzysztof Kozlowski <krzk@...nel.org>, linux-gpio@...r.kernel.org, 
	linux-kernel@...r.kernel.org, linux-acpi@...r.kernel.org, 
	Bartosz Golaszewski <bartosz.golaszewski@...aro.org>, Bartosz Golaszewski <brgl@...ev.pl>
Subject: Re: [PATCH v6 8/8] reset: gpio: use software nodes to setup the GPIO lookup

On Wed, 19 Nov 2025 09:19:30 +0100, Philipp Zabel <p.zabel@...gutronix.de> said:
> On Di, 2025-11-18 at 18:08 +0100, Bartosz Golaszewski wrote:
>> On Tue, Nov 18, 2025 at 5:44 PM Philipp Zabel <p.zabel@...gutronix.de> wrote:
>> >
>> > On Do, 2025-11-06 at 15:32 +0100, Bartosz Golaszewski wrote:
>> > > From: Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
>> > >
>> > > GPIO machine lookup is a nice mechanism for associating GPIOs with
>> > > consumers if we don't know what kind of device the GPIO provider is or
>> > > when it will become available. However in the case of the reset-gpio, we
>> > > are already holding a reference to the device and so can reference its
>> > > firmware node. Let's setup a software node that references the relevant
>> > > GPIO and attach it to the auxiliary device we're creating.
>> > >
>> > > Reviewed-by: Philipp Zabel <p.zabel@...gutronix.de>
>> > > Acked-by: Linus Walleij <linus.walleij@...aro.org>
>> > > Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
>> > > ---
>> >
>> > I'll apply this with the following patch squashed in:
>
> Strike that, I'll have to wait for the SPI issue to be resolved.
>
>> > diff --git a/drivers/reset/core.c b/drivers/reset/core.c
>> > index 3edf04ae8a95..8a7b112a9a77 100644
>> > --- a/drivers/reset/core.c
>> > +++ b/drivers/reset/core.c
>> > @@ -945,7 +945,7 @@ static int __reset_add_reset_gpio_device(const struct of_phandle_args *args)
>> >         of_node_get(rgpio_dev->of_args.np);
>> >
>> >         rgpio_dev->swnode = fwnode_create_software_node(properties, NULL);
>> > -       ret = PTR_ERR(rgpio_dev->swnode);
>> > +       ret = PTR_ERR_OR_ZERO(rgpio_dev->swnode);
>> >         if (ret)
>> >                 goto err_put_of_node;
>>
>> Huh? Why?
>
> PTR_ERR(ptr) is just (long)ptr, so a valid swnode pointer makes ret
> non-zero and takes us into the error path. PTR_ERR_OR_ZERO() includes
> the IS_ERR() check and returns 0 for non-error pointers.
>
> And there is a (false-positive) sparse warning:
>
>  drivers/reset/core.c:978 __reset_add_reset_gpio_device() warn: passing zero to 'PTR_ERR'
>
> I think it would be better to return to the explicit IS_ERR() check
> from v5.
>

Yes, it was like this in my initial submission and seems like it's more
readable and doesn't cause this confusion. I will go back to it. Though
I'm not sure if the SPI issue will require a v5 - I'm looking into fixing it
in the affected driver.

Bart