Re: [PATCH v4 1/2] software node: return -ENOTCONN when referenced swnode is not registered yet

Andy Shevchenko
2026-04-08T19:07:22Z

On Wed, Apr 8, 2026 at 9:53 PM Danilo Krummrich <dakr@kernel.org> wrote:
> On Wed Apr 8, 2026 at 5:52 PM CEST, Bartosz Golaszewski wrote:
> > On Wed, 8 Apr 2026 17:28:46 +0200, Danilo Krummrich <dakr@kernel.org> said:
> >> On Wed Apr 8, 2026 at 9:19 AM CEST, Bartosz Golaszewski wrote:
> >>> On Tue, Apr 7, 2026 at 3:28 PM Bartosz Golaszewski
> >>> <bartosz.golaszewski@oss.qualcomm.com> wrote:
> >>>>
> >>>> It's possible that at the time of resolving a reference to a remote
> >>>> software node, the node we know exists is not yet registered as a full
> >>>> firmware node. We currently return -ENOENT in this case but the same
> >>>> error code is also returned in some other cases, like the reference
> >>>> property with given name not existing in the property list of the local
> >>>> software node.
> >>>>
> >>>> It makes sense to let users know that we're dealing with an unregistered
> >>>> software node so that they can defer probe - the situation is somewhat
> >>>> similar to there existing a firmware node to which no device is bound
> >>>> yet - which is valid grounds for probe deferral. To that end: use
> >>>> -ENOTCONN to indicate the software node is "not connected".

> >>> With Andy's Ack, do you think you could still queue this for v7.1?
> >>
> >> Yeah, that should work, but I have a question about the patch.
> >>
> >> The comment added to fwnode_property_get_reference_args() says:
> >>
> >> + * %-ENOTCONN when the remote firmware node is a software node that
> >> + * has not been registered as a firmware node yet
> >>
> >> This seems like a bit of a layering violation to me, as it makes it explicit
> >> that this error code indicates a software node, while
> >> fwnode_property_get_reference_args() itself should be agnostic.
> >>
> >> The caller can easily derive more specific semantics with an is_software_node()
> >> check as you already do in the GPIO code.
> >>
> >> Can we describe the same condition, but without explicitly naming the backend?

> > Yes, sure. It can be something like:
> >
> > %-ENOTCONN when the remote firmware node exists but has not been
> > registered yet.

FWIW, good to me.

> > Does this sound good and doo you want me to resend or can you change it
> > when applying?
>
> I can change it when applying.
>
> One additional question though. I think it should be fine, but are we sure the
> change can't regress other subsystems? It seems some of them (e.g. sfp-bus,
> v4l2, iio) special case -ENOENT.

v4l2 uses the ENOTCONN in the cases similar to this

https://elixir.bootlin.com/linux/v7.0-rc7/source/drivers/media/v4l2-core/v4l2-async.c#L744

There are two more, but they seem more about connectors.

--
With Best Regards,
Andy Shevchenko