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