Advanced Configuration and Power Interface Specification

Advanced Configuration and Power Interface Specification
11.3.1 Fan Objects
11.3.1.1 _FIF (Fan Information)
The optional _FIF object provides OSPM with fan device capability information.
Arguments:
None
Return Value:
A Package containing the fan device parameters as described in Table 11-283 below
_FIF evaluation returns a package of the following format:
Package (){
Revision,
FineGrainControl,
StepSize
LowSpeedNotificationSupport
}
// Integer
// Integer Boolean
// Integer DWORD
// Integer Boolean
Table 11-283 FIF Package Details
Field Format Description
Revision Integer Current revision is: 0
Fine Grain
Control
Step Size
Low Speed
Notification
Support
Integer
(Boolean)
Integer
(DWORD)
Integer
(Boolean)
A non zero value in this field indicates OSPM may evaluate the fan device’s
_FSL object with a Level argument value in the range of 0-100, which
represents a percentage of maximum speed. A zero value in this field
indicates that OSPM may evaluate the fan device’s _FSL object with a Level
argument value that is a Control field value from a package in the _FPS
object’s package list only.
The recommended minimum step size in percentage points to be used
when OSPM performs fine-grained fan speed control. OSPM may utilize the
value of this field if the FineGrainControl field is non-zero the value in this
field is between 1 and 9.
A non zero value in this field indicates that the platform will issue a Notify
(0x80) to the fan device if a low (errant) fan speed is detected.
If a fan device supports fine-grained control, OSPM may evaluate a fan device’s _FSL object with
any Level argument value that is less than or equal to the Control field value specified in the package
of the _FPS object’s package list that corresponds to the active cooling trip point that has been
exceeded. This capability provides OSPM access to one hundred fan speed settings thus enabling
fine-grained fan speed control. The platform uses the StepSize field to help OSPM optimize its fan
level selection policy by fine-grained fan speed control. The platform uses the StepSize field to help
OSPM optimize its fan level selection policy by indicating recommended increments in the fan
speed level value that are appropriate for the fan when one percent increments are not optimal. In the
event OSPM’s incremental selections of Level using the StepSize field value do not sum to 100%,
OSPM may select an appropriate ending Level increment to reach 100%. OSPM should use the
same residual step value first when reducing Level.
604 April, 2015 Version 6.0