[phosphor-virtual-sensor] Add new feature to get Warning or Critical property

[Harvey Wu (吳崇維)]

> On Wed, Dec 30, 2020 at 10:19 AM Harvey Wu (吳崇維)
> <Harvey.Wu at quantatw.com> wrote:
> >
> > Hi All,
> >
> >
> >
> >         The current phosphor-virtual-sensor DbusParam value is from
> DBus “Value” property which interface is
> “xyz.openbmc_project.Sensor.Value”.
> >
> > Because I want to get the property “CriticalHigh” value on DBus, could I
> add a new feature “Interface” property in json file? The property can be
> “CriticalHigh” , “CriticalLow” , “WarningHigh” or “WarningLow”.
> 
> 
> According to
> https://apc01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgithub.
> com%2Fopenbmc%2Fphosphor-virtual-sensor%2Fblob%2Fmaster%2Fvirtual_
> sensor_config.json%23L8-L14&data=04%7C01%7CHarvey.Wu%40quantat
> w.com%7C1479ebd5aedd4b8a7c3308d8ac6a4393%7C179b032707fc4973ac73
> 8de7313561b2%7C1%7C0%7C637448919693850853%7CUnknown%7CTWFpb
> GZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6
> Mn0%3D%7C1000&sdata=0KyrnRkZKr9M59DEg%2BnyUruiege%2B3EDXb
> mxzR%2B6xeng%3D&reserved=0,
> the threshold properties are already supported.

The "Threshold" in json seems only can set the sensor critical or warning value, but I want to use the critical or warning value in "Expression".
After check the newest commit, this function seems doesn't implement in current source code.

> 
> --
> BRs,
> Lei YU


Harvey Wu