The type of sensor value in redfish should be double or int64?

[James Feist]

On 10/15/19 4:15 PM, Brad Bishop wrote:
> at 6:19 PM, Ed Tanous <ed.tanous at intel.com> wrote:
> 
>> On 10/15/19 12:04 PM, Brad Bishop wrote:
>>> Is it possible to get bmcweb supporting patch with double and int?  On
>>> the surface this seems like the shortest path to enabling Carol.
>>
>> Unless phosphor-hwmon is patched to support settable sensors, I don't
>> think there's a good reason to add support to bmcweb.
> 
> Ok.  A couple different questions then.
> 
> What does it mean to be settable?  phosphor-hwmon implements 
> Sensor.Value and, (in violation of the interface documentation), doesn’t 
> prevent an external application from writing to the properties in it.
> 
> I assumed the assertion that phosphor-hwmon doesn’t provide settable 
> sensors is because the value set by an external application doesn’t 
> stick?  The phosphor-hwmon application logic will write over it the next 
> time it polls the hwmon device.
> 
> So what does dbus-sensors do for hardware sensors?  Does the application 
> ignore the hardware state after being patched via Redfish?

Yes until the sensor is reset.


> 
>> With that said,
>> it's just software, it could certainly be done.  Someone would need to
>> sort out how to manage the scale factor, as a Redfish PATCH request
>> doesn't have a concept of scale, and operates on a float, so you'd have
>> to do some software handholding to convert the value to something
>> appropriate before it was scaled to the int64.
>>
>> With that said, all of this seems like a lot of work.
> 
> I don’t know of any alternatives that are less work.  If there are some, 
> I’d love to hear about them.  There were several years of OpenBMC 
> development against the integer interface signature before double became 
> a problem - as Patrick mentioned - undoing all that will not be trivial.
> 
>>
>> Just to clarify in case anyone isn't clear, the /xyz/* and /org/* type
>> REST handlers do support SetProperty for int and double, and introspects
>> the daemon to determine which one should be used.  So far as I'm aware,
>> the only thing non-functional is a Redfish patch of a sensor, as it's a
>> bit more complex to do properly.
> 
> I had a look at the Sensor schema in the latest Resource and Schema 
> guide and the sensor reading property is read only.  Why do we even 
> allow it to be patched?
> 

The intention was for this to only be in manufacturing test mode (not 
sure if that is true today or not). So under a normal user, it would be 
read only.

>>
>> -Ed
>