Device State D3 and System Wakeup
A version of this page is also available for
4/8/2010
The D3 device state has special semantics not strictly related to its power-consumption level. Devices in the D3 state can, but are not required to, awaken the system from a suspended state.
The following guidelines support the D3 state in device drivers:
- Devices that can awaken the system from a suspended state should not request the D3 state with DevicePowerNotify because enabling a device as a wake source is not always appropriate, unless the system is going to enter a suspended state. The driver cannot distinguish IOCTL_POWER_SET requests for D3 that it has initiated itself from those initiated by Power Manager as part of a system power state transition.
- If desired, wake-enabled devices can define D2 and D3 to be identical, except for enabling wake functionality.
- Devices that cannot awaken the system from a suspended state, but that do have a lowest power mode that can generate device activity can use D3 for self-management of power.
The above guidelines imply that devices that support D3 are not guaranteed to be able to awaken the system from a suspended state.
However, OEMs designing system power states and application developers calling SetPowerRequirement need to consider the special properties of the D3 state when the system as a whole is suspended. These guidelines enable OEMs and application developers to request that any device go into D3 during a suspended state without concern for whether the device actually supports waking the system.
For Windows Mobile:
See Also
Reference
DevicePowerNotify
IOCTL_POWER_SET
SetPowerRequirement