typedef struct _DEVICE_OBJECT_POWER_EXTENSION
{
     LONG IdleCount;
     ULONG ConservationIdleTime;
     ULONG PerformanceIdleTime;
     PDEVICE_OBJECT DeviceObject;
     LIST_ENTRY IdleList;
     UCHAR DeviceType;
     DEVICE_POWER_STATE State;
     LIST_ENTRY NotifySourceList;
     LIST_ENTRY NotifyTargetList;
     POWER_CHANNEL_SUMMARY PowerChannelSummary;
     LIST_ENTRY Volume;
     ULONG PreviousIdleCount;
} DEVICE_OBJECT_POWER_EXTENSION, *PDEVICE_OBJECT_POWER_EXTENSION;

Windows Vista Kernel Structures