PoRegisterForEffectivePowerModeNotifications function (wdm.h)

Article
05/22/2024

The PoRegisterForEffectivePowerModeNotifications function registers a callback to receive effective power mode change notifications.

Syntax

NTSTATUS PoRegisterForEffectivePowerModeNotifications(
  ULONG                             Version,
  PPO_EFFECTIVE_POWER_MODE_CALLBACK Callback,
  PVOID                             Context,
  PO_EPM_HANDLE                     *RegistrationHandle,
  PDEVICE_OBJECT                    DeviceObject
);

Parameters

Version

Supplies the maximum effective power mode version the caller understands. If the effective power mode comes from a later version, it is mapped to a compatible version that is then passed to the callback.

The following values can be passed in:

EFFECTIVE_POWER_MODE_V1 is available starting with Windows 10, version 1809 and tracks the performance power slider and energy saver states.
EFFECTIVE_POWER_MODE_V2 is available starting with Windows 10, version 1903 and tracks the performance power slider, battery saver, game mode and windows mixed reality power states.

Callback

A pointer to the callback to call when the effective power mode changes. This will also be called once upon registration to supply the current mode. If multiple callbacks are registered, those callbacks can be called concurrently.

Context

Caller-specified opaque context.

RegistrationHandle

This is a pointer to a variable that receives a handle to the registration. This handle can be used to unregister the callback function.

DeviceObject

This is an optional parameter that, if specified, provides a registered callback (such as from a driver) with the specified device context.

Return value

Returns S_OK (zero) if the call was successful, and a nonzero value if the call failed.

Remarks

Immediately after registration, the callback will be invoked with the current value of the power setting. If the registration occurs while the power mode is changing, you may receive multiple callbacks. The last callback is the most recent update.

Requirements

Requirement	Value
Minimum supported client	Windows 11, version 24H2
Header	wdm.h (include Wdm.h)
Library	NtosKrnl.lib
DLL	NtosKrnl.exe
IRQL	PASSIVE_LEVEL

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