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CHAPTER 8. SENSORS

IPMI UNIT TYPE RETRIES IPMI UNIT TYPE RESETS IPMI UNIT TYPE OVERRUNS IPMI UNIT TYPE UNDERRUNS IPMI UNIT TYPE COLLISIONS IPMI UNIT TYPE PACKETS IPMI UNIT TYPE MESSAGES IPMI UNIT TYPE CHARACTERS IPMI UNIT TYPE ERRORS IPMI UNIT TYPE CORRECTABLE ERRORS IPMI UNIT TYPE UNCORRECTABLE ERRORS IPMI UNIT TYPE FATAL ERRORS IPMI UNIT TYPE GRAMS The meanings of these values are not defined by the spec, but should be fairly obvious.

Threshold Sensor Hysteresis in OpenIPMI

OpenIPMI allows hysteresis to be fetched form a sensor and written to a sensor. Unfortunately, OpenIPMI does not have a very good way to represent the actual hysteresis value. The trouble is that hysteresis is not set per-threshold; it only has one hysteresis value that is applied to all thresholds for a sensor. This means that you cannot set a floating-point offset for hysteresis because the same floating-point hysteresis value may result in a different raw hysteresis value for each sensor2. This is one of the rare situations where IPMI could have been a bit more flexible (usually it is too flexible). Because of this situation, the hysteresis value is set as a raw value.

A separate positive and negative hysteresis can exist for a sensor. The positive value is for the “going higher” thresholds, it is the amount that must be subtracted from the threshold where the threshold will go back in range. The negative value is for the “going lower” thresholds, it is the amount that must be added to the threshold where the threshold will go back in range.

To know what type of hysteresis a sensor supports, use:

i n t i p m i _ s e n s o r _ g e t _ h y s t e r e s i s _ s u p p o r t ( i p m i _ s e n s o r _ t * s e n s o r This returns one of the following values: IPMI HYSTERESIS SUPPORT NONE - The sensor does not support hysteresis. ) ;

IPMI HYSTERESIS SUPPORT READABLE - The sensor has hysteresis, but the value cannot be set. It can be read.

IPMI HYSTERESIS SUPPORT SETTABLE - The sensor has hysteresis and the value can be both set and read.

IPMI HYSTERESIS SUPPORT FIXED - The sensor has hysteresis but the value cannot be read or set. If the default hysteresis values are non-zero, then they are the fixed hysteresis for the sensor. Otherwise the values are unknown.

The default hystersis can be read using:

2This is due to the fact that some sensors are non-linear.

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