EvtDevicePowerPolicyStateChange function
[Applies to KMDF only]
A driver's EvtDevicePowerPolicyStateChange event callback function informs the driver that a device's power policy state machine is moving from one state to another.
Syntax
EVT_WDF_DEVICE_POWER_POLICY_STATE_CHANGE_NOTIFICATION EvtDevicePowerPolicyStateChange;
VOID EvtDevicePowerPolicyStateChange(
_In_ WDFDEVICE Device,
_In_ PCWDF_DEVICE_POWER_POLICY_NOTIFICATION_DATA NotificationData
)
{ ... }
Parameters
- Device [in]
-
A handle to a framework device object.
- NotificationData [in]
-
A pointer to a framework-supplied WDF_DEVICE_POWER_POLICY_NOTIFICATION_DATA structure that identifies the state machine's old and new states.
Return value
None
Remarks
To register an EvtDevicePowerPolicyStateChange callback function, a driver must call WdfDeviceInitRegisterPowerPolicyStateChangeCallback.
Most drivers do not need to be notified when the framework's power policy state machine changes state. For more information, see State Machines in the Framework.
If the EvtDevicePowerPolicyStateChange callback function calls WdfDeviceStopIdle with the WaitForD0 parameter set to TRUE, the framework's power policy state machine will become deadlocked.
Examples
To define an EvtDevicePowerPolicyStateChange 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 EvtDevicePowerPolicyStateChange callback function that is named MyDevicePowerPolicyStateChange, use the EVT_WDF_DEVICE_POWER_POLICY_STATE_CHANGE_NOTIFICATION type as shown in this code example:
EVT_WDF_DEVICE_POWER_POLICY_STATE_CHANGE_NOTIFICATION MyDevicePowerPolicyStateChange;
Then, implement your callback function as follows:
_Use_decl_annotations_
VOID
MyDevicePowerPolicyStateChange (
WDFDEVICE Device,
PCWDF_DEVICE_POWER_POLICY_NOTIFICATION_DATA NotificationData
)
{...}
The EVT_WDF_DEVICE_POWER_POLICY_STATE_CHANGE_NOTIFICATION 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_POWER_POLICY_STATE_CHANGE_NOTIFICATION 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 |
|---|---|
|
Header |
|
|
IRQL | PASSIVE_LEVEL |
See also
