Re: [PATCH 7/8] hwmon: (scmi) Register explicitly with Thermal Framework

[Guenter Roeck]

On 10/28/22 09:15, Cristian Marussi wrote:
> On Fri, Oct 28, 2022 at 08:58:58AM -0700, Guenter Roeck wrote:
> > On 10/28/22 08:35, Cristian Marussi wrote:
> > [ ... ]
> > > > > +	/*
> > > > > +	 * Try to register a temperature sensor with the Thermal Framework:
> > > > > +	 * skip sensors not defined as part of any thermal zone (-ENODEV) but
> > > > > +	 * report any other errors related to misconfigured zones/sensors.
> > > > > +	 */
> > > > > +	tzd = devm_thermal_of_zone_register(dev, th_sensor->info->id, th_sensor,
> > > > > +					    &scmi_hwmon_thermal_ops);
> > > > > +	if (IS_ERR(tzd)) {
> > > > > +		devm_kfree(dev, th_sensor);
> > > > > +
> > > > > +		if (PTR_ERR(tzd) != -ENODEV)
> > > > > +			return PTR_ERR(tzd);
> > > > > +
> > > > > +		dev_info(dev, "Sensor '%s' not attached to any thermal zone.\n",
> > > > > +			 sensor->name);
> > > >
> > > > There were complaints about this message as it is noisy. If you send
> > > > another version, please drop it unless attaching each sensor to a thermal
> > > > zone is strongly expected. If you don't send another version, I'll drop it
> > > > while applying.
> > >
> > > Ok fine for me. I am waiting to have some feedback from Sudeep too, but
> > > I do not have plan for another version as of now.
> > >
> > > As a side note, though, I understand the 'noisiness' argument, but,
> > > sincerely this same message in the original HWMON code was the only
> > > reason why I spotted that something was wrong with the SCMI/HWMON
> > > interactions and discovered the indexes/ids mismatch...if not for
> > > that it would have gone un-noticed that a perfectly configured
> > > ThermalZone/Sensor was not working properly...
> > > (un-noticed at least until something would have been burnt to fire
> > >    in my house .. joking :P)
> >
> > Good point.
> >
> > Did you ever check the returned error code ? Maybe we could use it to
> > distinguish "it is not attached to a thermal zone because it is not
> > associated with one" from "attaching to a thermal zone failed because
> > its configuration is bad/incomplete".
>
> Yes, it is what I do already indeed, in this regards I mimicked what
> the hwmon-thermal bridge was doing.
>
> In scmi_thermal_sensor_register() this message is printed out only
> if Thermal registration returned -ENODEV and no err is reported
> (which means teh specified sensor was not found attached to any TZ),
> while in the caller of scmi_thermal_sensor_register() for any error
> returned but -ENOMEM I print:
>
> 	"Thermal zone misconfigured for %s. err=%d\n",
>
> since any error reported by Thermal other than ENODEV and ENOMEM
> means the DT parsing unveiled some configuration anomaly.

Ok, then let's hope that this finds misconfigurations and drop the
info message.

I just noticed another problem in your code:

+		if (ret == -ENOMEM)
+			return ret;
+		else if (ret)
+			dev_warn(dev,
+				 "Thermal zone misconfigured for %s. err=%d\n",
+				 sensor->name, ret);

Static analyzers will rightfully notice that else after return is unnecessary.
Please rewrite and drop the else. I think something like

		if (ret) {
			if (ret == -ENOMEM)
				return ret;
			dev_warn(dev,
				 "Thermal zone misconfigured for %s. err=%d\n",
				 sensor->name, ret);
		}

would be better since ret would only be evaluated once in the no-error case.

Thanks,
Guenter