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EvtDeviceWakeFromSxTriggered function

[Applies to KMDF and UMDF]

A driver's EvtDeviceWakeFromSxTriggered event callback function informs the driver that its device, which had previously entered a low-power device state because system power was reduced, might have triggered a wake signal.

Syntax


EVT_WDF_DEVICE_WAKE_FROM_SX_TRIGGERED EvtDeviceWakeFromSxTriggered;

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

Parameters

Device [in]

A handle to a framework device object.

Return value

None

Remarks

To register an EvtDeviceWakeFromSxTriggered 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 EvtDeviceDisarmWakeFromSx 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 EvtDeviceWakeFromSxTriggered 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 EvtDeviceDisarmWakeFromSx 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 System Wake-Up.

Examples

To define an EvtDeviceWakeFromSxTriggered 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 EvtDeviceWakeFromSxTriggered callback function that is named MyDeviceWakeFromSxTriggered, use the EVT_WDF_DEVICE_WAKE_FROM_SX_TRIGGERED type as shown in this code example:


EVT_WDF_DEVICE_WAKE_FROM_SX_TRIGGERED  MyDeviceWakeFromSxTriggered;

Then, implement your callback function as follows:


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

The EVT_WDF_DEVICE_WAKE_FROM_SX_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_SX_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

EvtDeviceArmWakeFromSx
EvtDeviceDisarmWakeFromSx
EvtDeviceWakeFromS0Triggered

 

 

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