Re: [PATCH v2 1/4] software node: return -ENXIO when referenced swnode is not registered yet

Bartosz Golaszewski
2026-04-07T10:57:42Z

On Fri, Apr 3, 2026 at 8:07 PM Dmitry Torokhov
<dmitry.torokhov@gmail.com> wrote:
>
> On Fri, Apr 03, 2026 at 09:29:38AM +0200, Bartosz Golaszewski wrote:
> > On Thu, Apr 2, 2026 at 10:43 PM Dmitry Torokhov
> > <dmitry.torokhov@gmail.com> wrote:
> > >
> > > On Thu, Apr 02, 2026 at 04:35:34PM +0300, Andy Shevchenko wrote:
> > > > On Thu, Apr 02, 2026 at 02:54:26PM +0200, Bartosz Golaszewski 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 -ENXIO
> > > > > which stands for "No such device or address".
> > > >
> > > > This error code is also too generic to my taste. What about alternative(s)?
> > > > EADDRNOTAVAIL
> > > > ENOTCONN
> > > >
> > > > (The brief grep shows that the second one might suit slightly better than the
> > > > first one by existing use cases.)
> > >
> > > We are in the core of the driver core. Why not simply use -EPROBE_DEFER
> > > to which all users will resolve this error to and call it a day?
> > >
> >
> > Because -EPROBE_DEFER only makes sense in probe() context, while
> > fwnode_get_reference_args() may be called in many other situations.
>
> Exactly same argument applies to your follow-up change: gpiod_get()
> returning -EPROBE_DEFER only makes sense in probe context but it may be
> called in many other situations. Are you planning to change all places
> where gpiolib returns -EPROBE_DEFER to something else just in case it
> might be called outside of probe context?
>

I'd argue that gpiod_get() should really be limited to being called at
probe() time but I see your point.

> -EPROBE_DEFER should have been called -ENOTREADY from the beginning and
> then we would not have this argument. Or, even better, we should have
> used -EAGAIN. But it is just a name, semantics does not really change.
> We want to signal that something is not ready and the operation needs be
> repeated. Currently we contorting ourselves by using yet another error
> code that everyone will either convert to -EPORBE_DEFER or will handle
> like -EAGAIN.
>
> > I think ENOTCONN as "not connected" makes sense, though the string
>
> Why is it better? Most of users of -ENOTCONN are in networking code so
> it is somewhat unexpected to have other APIs return it.
>
> > representation says: "Transport endpoint is not connected" which
> > doesn't spell out quite the same thing.
>
> Yes, because it is really for networking/sockets handling.
>
> Thanks.
>

Andy et al: what is your take on this?

Bart