IPowerNotify::PowerChangeNotify method (portcls.h)

Article
10/21/2021

The PowerChangeNotify method notifies the miniport driver of changes in the power state.

Syntax

void PowerChangeNotify(
  [in] POWER_STATE PowerState
);

Parameters

[in] PowerState

Specifies the current power state. This parameter is a union of type POWER_STATE. The new power state (PowerState.DeviceState) can be one of the DEVICE_POWER_STATE enumeration values listed in IAdapterPowerManagement::PowerChangeState.

Return value

None

Remarks

The PortCls system driver calls the miniport driver's PowerChangeNotify method to notify it of changes in the power state. The purpose of this call is to give the miniport driver an opportunity to save any hardware-specific context just before powering down or to restore a previously saved context just after powering up.

The miniport driver can write to the hardware registers or on-board memory during the PowerChangeNotify call. If the system is powering down (making a state transition away from PowerDeviceD0), the PortCls system driver calls PowerChangeNotify before it calls IAdapterPowerManagement::PowerChangeState and after it has paused any active audio data streams. This gives the miniport driver an opportunity to save any hardware-specific device context before the device powers down. For example, a WavePci miniport driver might need to save its DMA registers if the power down occurs during a sequence of scatter/gather data transfers. If the system is powering up (making a state transition toward PowerDeviceD0), PortCls calls PowerChangeNotify after it calls PowerChangeState and before it restarts any paused audio data streams. This gives the miniport driver an opportunity to restore a previously saved context after the device has powered up.

The code for this method must reside in paged memory.

Requirements

Requirement	Value
Target Platform	Universal
Header	portcls.h (include Portcls.h)