Re: [PATCH v2 2/4] gpio: swnode: defer probe on references to unregistered software nodes

[Bartosz Golaszewski]

On Thu, Apr 2, 2026 at 11:04 PM Dmitry Torokhov
<dmitry.torokhov@xxxxxxxxx> wrote:
>
> On Thu, Apr 02, 2026 at 02:54:27PM +0200, Bartosz Golaszewski wrote:
> > fwnode_property_get_reference_args() now returns -ENXIO when called on a
> > software node referencing another software node which has not yet been
> > registered as a firmware node. It makes sense to defer probe in this
> > situation as the node will most likely be registered later on and we'll
> > be able to resolve the reference eventually. Change the behavior of
> > swnode_find_gpio() to return -EPROBE_DEFER if the software node reference
> > resolution returns -ENXIO.
> >
> > Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@xxxxxxxxxxxxxxxx>
> > ---
> >  drivers/gpio/gpiolib-swnode.c | 9 +++++++++
> >  1 file changed, 9 insertions(+)
> >
> > diff --git a/drivers/gpio/gpiolib-swnode.c b/drivers/gpio/gpiolib-swnode.c
> > index 0d7f3f09a0b4bee0cf1bbdaa8b7b8ae4cd5de581..06d74e9e199de0b91a019e5e15d4b83d330291e7 100644
> > --- a/drivers/gpio/gpiolib-swnode.c
> > +++ b/drivers/gpio/gpiolib-swnode.c
> > @@ -95,6 +95,15 @@ struct gpio_desc *swnode_find_gpio(struct fwnode_handle *fwnode,
> >                       break;
> >       }
> >       if (ret) {
> > +             if (ret == -ENXIO)
>
>
> I'll be just sitting here and quoting sashiko all day long ;)
>

I would love it to produce briefer messages. I'm always put off by the
walls of text. I would literally rather deal with neanderthal mode
like: "loop continues on ret != 0, bad!".

> "
> If swnode_gpio_get_reference() returns -ENXIO during the first iteration
> (for example, when checking the con_id-gpios suffix), won't the loop continue
> since the return value is not 0?
>
> Looking at the loop just above this block:
>
>         for_each_gpio_property_name(propname, con_id) {
>                 ret = swnode_gpio_get_reference(fwnode, propname, idx, &args);
>                 if (ret == 0)
>                         break;
>         }
>
> If the initial property check returns -ENXIO, but the subsequent fallback
> check for the con_id-gpio suffix returns -ENOENT, the ret variable gets
> overwritten.
>
> When the loop terminates, ret would be -ENOENT instead of -ENXIO. Could this
> cause the probe deferral check to evaluate to false and fail the probe
> entirely instead of deferring it as intended?
>
> Should the loop also break early if -ENXIO is encountered?
>
> "
>
> You need to change that to
>
>         if (ret == 0 || ret == -ENXIO)
>                 break;
>
> because if we get -ENXIO that means the GPIO must be there (the property
> exists) but not ready yet and we do not want to fall back to another
> suffix.
>

Yes, thanks.

Bart