Contents

powerStateDidChangeTo

Informs interested parties that a device has changed to a different power state.

Declaration

virtual IOReturn powerStateDidChangeTo( 
 IOPMPowerFlagscapabilities, 
 unsigned longstateNumber, 
 IOService *whatDevice );

Parameters

  • capabilities:

    Flags that describe the capability of the device in the new power state (they come from the capabilityFlags field of the new state in the power state array).

  • stateNumber:

    The number of the state in the state array that the device is switching to.

  • whatDevice:

    A pointer to the driver that is changing. It can be used by a driver that is receiving power state change notifications for multiple devices to distinguish between them.

Return Value

The driver returns IOPMAckImplied if it has prepared for the power change when it returns. If it has started preparing but not finished, it should return a number of microseconds which is an upper limit of the time it will need to finish preparing. Then, when it has completed its preparations, it should call acknowledgePowerChange.

Overview

Power management informs interested parties that a device has changed to a different power state. Interested parties are those that have registered for this notification via registerInterestedDriver. If you have called registerInterestedDriver on a power managed driver, you must implemnt powerStateWillChangeTo and powerStateDidChangeTo to receive the notifications. powerStateDidChangeTo is called in a clean and separate thread context. powerStateWillChangeTo is called before a power state transition takes place; powerStateDidChangeTo is called after the transition has completed.

See Also

Miscellaneous