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Device State D3 and System Wakeup (Windows Embedded CE 6.0)

  • Article

1/6/2010

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.

See Also

Reference

DevicePowerNotify
IOCTL_POWER_SET
SetPowerRequirement

Concepts

Device Power States

Other Resources

Device Power Management Guidelines
XXX_PowerDown (Device Manager)
XXX_PowerUp (Device Manager)