Contents

activityTickle

Informs power management when a power-managed device is in use, so that power management can track when it is idle and adjust its power state accordingly.

Declaration

virtual bool activityTickle( 
 unsigned long type, 
 unsigned long stateNumber = 0 );

Parameters

  • type:

    When type is kIOPMSubclassPolicy, activityTickle is not handled in IOService and should be intercepted by the subclass. When type is kIOPMSuperclassPolicy1, an activity flag is set and the device state is checked. If the device has been powered down, it is powered up again.

  • stateNumber:

    When type is kIOPMSuperclassPolicy1, stateNumber contains the desired power state ordinal for the activity. If the device is in a lower state, the superclass will switch it to this state. This is for devices that can handle some accesses in lower power states; the device is powered up only as far as it needs to be for the activity.

Return Value

When type is kIOPMSuperclassPolicy1, the superclass returns true if the device is currently in the state specified by stateNumber. If the device is in a lower state and must be powered up, the superclass returns false; in this case the superclass will initiate a power change to power the device up.

Overview

The activityTickle method is provided for objects in the system (or for the driver itself) to tell a driver that its device is being used. The IOService superclass can manage idleness determination with a simple idle timer mechanism and this activityTickle call. To start this up, the driver calls its superclass's setIdleTimerPeriod. This starts a timer for the time interval specified in the call. When the timer expires, the superclass checks to see if there has been any activity since the last timer expiration. (It checks to see if activityTickle has been called). If there has been activity, it restarts the timer, and this process continues. When the timer expires, and there has been no device activity, the superclass lowers the device power state to the next lower state. This can continue until the device is in state zero. After the device has been powered down by at least one power state, a subsequent call to activityTickle causes the device to be switched to a higher state required for the activity. If the driver is managing the idleness determination totally on its own, the value of the type parameter should be kIOPMSubclassPolicy, and the driver should override the activityTickle method. The superclass IOService implementation of activityTickle does nothing with the kIOPMSubclassPolicy argument.

See Also

Miscellaneous