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

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Message-Id: <c7e1272a-c9c8-a120-632f-7693cef3fd22@linux.vnet.ibm.com>
Date:   Wed, 4 Jul 2018 22:23:51 +0530
From:   Shilpasri G Bhat <shilpa.bhat@...ux.vnet.ibm.com>
To:     Guenter Roeck <linux@...ck-us.net>, mpe@...erman.id.au
Cc:     linuxppc-dev@...ts.ozlabs.org, linux-hwmon@...r.kernel.org,
        linux-kernel@...r.kernel.org, ego@...ux.vnet.ibm.com
Subject: Re: [PATCH v2 2/2] hwmon: ibmpowernv: Add attributes to
 enable/disable sensor groups

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.

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

Thanks and Regards,
Shilpa