PO_FX_COMPONENT_CRITICAL_TRANSITION_CALLBACK callback function (wdm.h)

Article
02/25/2022

The ComponentCriticalTransitionCallback callback routine handles a transition of the specified component between the F0 (fully on) and low-power Fx component power states.

Syntax

PO_FX_COMPONENT_CRITICAL_TRANSITION_CALLBACK PoFxComponentCriticalTransitionCallback;

void PoFxComponentCriticalTransitionCallback(
  [in] PVOID Context,
  [in] ULONG Component,
  [in] BOOLEAN Active
)
{...}

Parameters

[in] Context

A pointer to the device context. The device driver uses this context to store information about the current power state of the device. This context is driver-defined and is opaque to PoFx. The driver specified this pointer in the DeviceContext member of the PO_FX_CORE_DEVICE structure that the driver used to register the device with the Windows power management framework (PoFx).

[in] Component

The index that identifies the component. This parameter is an index into the Components array in the PO_FX_CORE_DEVICE structure that the device driver used to register the device with PoFx. If the Components array contains N elements, component indexes range from 0 to N–1.

[in] Active

Indicates whether this notification is for a transition to the F0 component power state. If TRUE, the component has just completed a transition from a low-power Fx state to F0. If FALSE, the component is about to start a transition from F0 to a low-power Fx state.

Return value

None

Remarks

This callback routine is implemented by a device driver, and is called by PoFx. PoFx calls this routine to notify the driver of power transitions of device components.

The ComponentCriticalTransitionCallback member of the PO_FX_CORE_DEVICE structure is a pointer to a ComponentCriticalTransitionCallback callback routine. A pointer to a PO_FX_CORE_DEVICE structure is passed as an input parameter in the PoFxRegisterCoreDevice call that registers a core device with the Windows power management framework (PoFx).

To handle calls to this routine, the device driver saves or restores the register state or other hardware context of the specified component in the device.

If Active = TRUE, PoFx has called this routine after the component completed a transition from a low-power Fx state to F0. In this call, the routine restores the previously saved hardware context of the component.

If Active = FALSE, PoFx has called this routine before the component starts a pending transition from F0 to a low-power Fx state. In this call, the routine saves the component's hardware context so that this context can later be restored.

For more information about Fx component power states, see Component-Level Power Management.

Requirements

Requirement	Value
Minimum supported client	Supported starting with Windows 10.
Target Platform	Windows
Header	wdm.h (include Wudfwdm.h)