Re: [PATCH v2 2/2] hwmon: ibmpowernv: Add attributes to enable/disable sensor groups

[Guenter Roeck]

On 07/04/2018 09:53 AM, Shilpasri G Bhat wrote:
> Hi Guenter,
>
> Thanks for reviewing the patch.
> On 07/04/2018 08:16 PM, Guenter Roeck wrote:
> > > +        /* Disable if last sensor in the group */
> > > +        send_command = true;
> > > +        for (i = 0; i < sg->nr_sensor; i++) {
> > > +            struct sensor_data *sd = sg->sensors[i];
> > > +
> > > +            if (sd->enable) {
> > > +                send_command = false;
> > > +                break;
> > > +            }
> >
> > This is weird. So there are situations where a request to disable
> > a sensor is accepted, but effectively ignored ? Shouldn't that
> > return, say, -EBUSY ?
>
> This is because we do not support per-sensor enable/disable. We can only
> enable/disable at a sensor-group level.
>
> This patch follows the semantic to disable a sensor group iff all the sensors
> belonging to that group have been disabled. Otherwise the sensor alone is marked
> to be disabled and returns -ENODATA on reading it.
>
> And a sensor group will be enabled if any of the sensor in that group is enabled.

In similar situations, where setting one attribute affects others, a common solution
is to make only the first attribute writable and have it affect all the others.
I think that would make sense here as well, and it would be much simpler to implement.

Guenter

> I will make changes to the remaining code according to your suggestion.
>
> Thanks and Regards,
> Shilpa
>
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