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EVT_WDF_DEVICE_ARM_WAKE_FROM_S0 callback function (wdfdevice.h)

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[Applies to KMDF and UMDF]

A driver's EvtDeviceArmWakeFromS0 event callback function arms (that is, enables) a device so that it can trigger a wake signal while in a low-power device state, if the system remains in the system working state (S0).

Syntax

EVT_WDF_DEVICE_ARM_WAKE_FROM_S0 EvtWdfDeviceArmWakeFromS0;

NTSTATUS EvtWdfDeviceArmWakeFromS0(
  [in] WDFDEVICE Device
)
{...}

Parameters

[in] Device

A handle to a framework device object.

Return value

If the operation is successful, the EvtDeviceArmWakeFromS0 callback function must return STATUS_SUCCESS or another status value for which NT_SUCCESS(status) equals TRUE. Otherwise it must return a status value for which NT_SUCCESS(status) equals FALSE.

If NT_SUCCESS(status) equals FALSE, the framework does not call the driver's EvtDeviceDisarmWakeFromS0 callback function. (The framework does not report a device failure to the PnP manager.)

Remarks

To register an EvtDeviceArmWakeFromS0 callback function, a driver must call WdfDeviceInitSetPowerPolicyEventCallbacks. Additionally, the driver must set IdleCanWakeFromS0 in the IdleCaps member of its WDF_DEVICE_POWER_POLICY_IDLE_SETTINGS structure.

The EvtDeviceArmWakeFromS0 callback function handles device-specific operations that are needed to enable the device to detect an external event that triggers a wake signal on the bus. The bus driver's EvtDeviceEnableWakeAtBus callback function handles bus-specific operations, such as enabling the PCI bus's Power Management Event (PME) signal.

If the driver has registered an EvtDeviceArmWakeFromS0 callback function, the framework calls it while the device is still in the D0 device power state, before the bus driver lowers the device's power state but after the framework has sent a wait/wake IRP on behalf of the driver.

The process occurs in the following sequence:

  1. The framework determines that the device has been idle for a preset amount of time.
  2. The framework calls the driver's EvtDeviceArmWakeFromS0 callback function.
  3. The framework requests the driver for the device's bus to lower the device's power.
Immediately before your device enters a low power state, the framework will call your driver's EvtDeviceD0Exit callback function.

For more information about when the framework calls this callback function, see PnP and Power Management Scenarios.

You do not need to provide an EvtDeviceArmWakeFromS0 callback function if your device:

  • Is a USB device that supports "selective suspend."
  • Cannot be powered down while the system remains fully powered.
  • Does not require special hardware operations that enable the device to trigger a wake signal.
If your device supports USB "selective suspend" and if your driver sets IdleUsbSelectiveSuspend in the IdleCaps member of its WDF_DEVICE_POWER_POLICY_IDLE_SETTINGS structure, the framework sends a "selective suspend" request to the USB bus driver when the device has been idle for a preset amount of time.

For more information about this callback function, see Supporting Idle Power-Down.

Requirements

Requirement Value
Target Platform Universal
Minimum KMDF version 1.0
Minimum UMDF version 2.0
Header wdfdevice.h (include Wdf.h)
IRQL PASSIVE_LEVEL

See also

EvtDeviceArmWakeFromSx

EvtDeviceDisarmWakeFromS0