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

From: Guenter Roeck
Date: Wed Jul 04 2018 - 17:43:06 EST

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.


I will make changes to the remaining code according to your suggestion.

Thanks and Regards,

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