iokit/IOKit/IOService.h

1440     <li>Call <code>changePowerStateTo</code> in conjunction with @link setIdleTimerPeriod setIdleTimerPeriod@/link and @link activityTickle activityTickle@/link to idle a driver into a low power state. For a driver with 3 power states, for example, <code>changePowerStateTo(1)</code> sets a minimum level of power state 1, such that the idle timer period may not set your device's power any lower than state 1.</ul>
1462 /*! @function activityTickle
1464     @discussion The <code>activityTickle</code> method is provided for objects in the system (or for the driver itself) to tell a driver that its device is being used.
1465     The IOService superclass can manage idleness determination with a simple idle timer mechanism and this <code>activityTickle</code> call. To start this up, the driver calls its superclass's <code>setIdleTimerPeriod</code>. 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 <code>activityTickle</code> 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.
1466     After the device has been powered down by at least one power state, a subsequent call to <code>activityTickle</code> causes the device to be switched to a higher state required for the activity.
1467     If the driver is managing the idleness determination totally on its own, the value of the <code>type</code> parameter should be <code>kIOPMSubclassPolicy</code>, and the driver should override the <code>activityTickle</code> method. The superclass IOService implementation of <code>activityTickle</code> does nothing with the <code>kIOPMSubclassPolicy</code> argument.
1468     @param type When <code>type</code> is <code>kIOPMSubclassPolicy</code>, <code>activityTickle</code> is not handled in IOService and should be intercepted by the subclass. When <code>type</code> is <code>kIOPMSuperclassPolicy1</code>, an activity flag is set and the device state is checked. If the device has been powered down, it is powered up again.
1472     virtual bool activityTickle(
1574     @discussion A driver using the idleness determination provided by IOService calls its superclass with this method to set or change the idle timer period. See @link activityTickle activityTickle@/link for a description of this type of idleness determination.