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EvtDeviceWakeFromS0Triggered function

[Applies to KMDF and UMDF]

A driver's EvtDeviceWakeFromS0Triggered event callback function informs the driver that its device, which had previously entered a low-power device state while the system power state remained at S0, might have triggered a wake signal.

Syntax


EVT_WDF_DEVICE_WAKE_FROM_S0_TRIGGERED EvtDeviceWakeFromS0Triggered;

VOID EvtDeviceWakeFromS0Triggered(
  _In_  WDFDEVICE Device
)
{ ... }

Parameters

Device [in]

A handle to a framework device object.

Return value

None

Remarks

To register an EvtDeviceWakeFromS0Triggered callback function, a driver must call WdfDeviceInitSetPowerPolicyEventCallbacks.

If the driver has registered this callback, the framework calls it after calling the driver's EvtDeviceD0Entry callback function and before calling the driver's EvtDeviceDisarmWakeFromS0 callback function.

System hardware (BIOSes, motherboards, bus adapters) can sometimes drop a wake signal before the bus driver detects it, even though the signal wakes up the system. In such cases, the driver's EvtDeviceWakeFromS0Triggered callback function will not be called even though the driver's device triggered a wake signal.

Some buses combine wake signals from several children. If your device is connected to one of these buses, the callback function might have to determine if the current device triggered the wake-up signal. If your device provides a hardware latch that saves the device's triggered state, it is best to check that state in the driver's EvtDeviceDisarmWakeFromS0 callback function, because that callback is always called after the device wakes up, even if the wake signal was dropped.

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

Examples

To define an EvtDeviceWakeFromS0Triggered callback function, you must first provide a function declaration that identifies the type of callback function you’re defining. Windows provides a set of callback function types for drivers. Declaring a function using the callback function types helps Code Analysis for Drivers, Static Driver Verifier (SDV), and other verification tools find errors, and it’s a requirement for writing drivers for the Windows operating system.

For example, to define an EvtDeviceWakeFromS0Triggered callback function that is named MyDeviceWakeFromS0Triggered, use the EVT_WDF_DEVICE_WAKE_FROM_S0_TRIGGERED type as shown in this code example:


EVT_WDF_DEVICE_WAKE_FROM_S0_TRIGGERED  MyDeviceWakeFromS0Triggered;

Then, implement your callback function as follows:


_Use_decl_annotations_
VOID
 MyDeviceWakeFromS0Triggered (
    WDFDEVICE  Device
    )
  {...}

The EVT_WDF_DEVICE_WAKE_FROM_S0_TRIGGERED function type is defined in the Wdfdevice.h header file. To more accurately identify errors when you run the code analysis tools, be sure to add the _Use_decl_annotations_ annotation to your function definition. The _Use_decl_annotations_ annotation ensures that the annotations that are applied to the EVT_WDF_DEVICE_WAKE_FROM_S0_TRIGGERED function type in the header file are used. For more information about the requirements for function declarations, see Declaring Functions by Using Function Role Types for KMDF Drivers. For information about _Use_decl_annotations_, see Annotating Function Behavior.

Requirements

Minimum KMDF version

1.0

Minimum UMDF version

2.0

Header

Wdfdevice.h (include Wdf.h)

IRQL

PASSIVE_LEVEL

See also

EvtDeviceArmWakeFromS0
EvtDeviceDisarmWakeFromS0
EvtDeviceWakeFromSxTriggered

 

 

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