Re: [PATCH] powerpc/powernv : Add support to enable sensor groups

Shilpasri G Bhat [off-list ref] writes:

On 12/04/2017 10:11 AM, Stewart Smith wrote:

quoted

Shilpasri G Bhat [off-list ref] writes:

quoted

On 11/28/2017 05:07 PM, Michael Ellerman wrote:

quoted

Shilpasri G Bhat [off-list ref] writes:

quoted

Adds support to enable/disable a sensor group. This can be used to
select the sensor groups that needs to be copied to main memory by
OCC. Sensor groups like power, temperature, current, voltage,
frequency, utilization can be enabled/disabled at runtime.

Signed-off-by: Shilpasri G Bhat <redacted>
---
The skiboot patch for the opal call is posted below:
https://lists.ozlabs.org/pipermail/skiboot/2017-November/009713.html

Can you remind me why we're doing this with a completely bespoke sysfs
API, rather than using some generic sensors API?

Disabling/Enabling sensor groups is not supported in the current generic sensors
API. And also we dont export all type of sensors in HWMON as not all of them are
environment sensors (like performance).

Are there barriers to adding such concepts to the generic sensors API?

Yes.

HWMON does not support attributes for a sensor-group. If we are to extend HWMON
to add new per-sensor attributes to disable/enable, then we need to do either of
the below:

1) If any one of the sensor is disabled then all the sensors belonging to that
group will be disabled. OR

2) To disable a sensor group we need to disable all the sensors belonging to
that group.

Either of those sound doable, the first is probably simpler, as long as
there's some way for userspace to understand that it is modifying the
state of the whole group.

Another problem is hwmon categorizes the sensor-groups based on the type of
sensors like power, temp. If OCC allows multiple groups of the same type then
this approach adds some more complexity to the user to identify the sensors
belonging to correct group.

I don't really understand this one, what do you mean by "If OCC allows"?

Also do we really expect users to be using this API? Or rather tools?

And lastly HWMON does not allow platform specific non-standard sensor groups
like CSM, job-scheduler, profiler.

Have we actually made specific proposals to the hwmon maintainers on
adding/changing any of the above? Have they rejected those proposals and
told us to go away?

cheers