WDF_POWER_POLICY_S0_IDLE_CAPABILITIES enumeration

[Applies to KMDF and UMDF]

The WDF_POWER_POLICY_S0_IDLE_CAPABILITIES enumeration identifies the capabilities that a device can support when it enters a low-power state while it is idling.

Syntax

C++


typedef enum _WDF_POWER_POLICY_S0_IDLE_CAPABILITIES { 
  IdleCapsInvalid          = 0,
  IdleCannotWakeFromS0     = 1,
  IdleCanWakeFromS0        = 2,
  IdleUsbSelectiveSuspend  = 3
} WDF_POWER_POLICY_S0_IDLE_CAPABILITIES;

Constants

IdleCapsInvalid

For internal use only.

IdleCannotWakeFromS0

The device cannot wake itself from a low-power state while the system is in its working (S0) state.

IdleCanWakeFromS0

The device can wake itself from a low-power state while the system is in its working (S0) state.

IdleUsbSelectiveSuspend

The device is connected to a USB bus and supports USB selective suspend. Use this value if your USB-connected device supports both idling and waking itself while the computer is in its working state. If your USB device supports only idling, use IdleCannotWakeFromS0. (Drivers for USB devices must not specify IdleCanWakeFromS0.) See the code examples in the following Examples section.

For Windows XP, the framework supports USB selective suspend only if the device's USB_CONFIGURATION_DESCRIPTOR structure shows that the device supports remote wakeup. For Windows Vista and later versions of Windows, the framework supports USB selective suspend whether or not the device supports remote wakeup.

Remarks

The WDF_POWER_POLICY_S0_IDLE_CAPABILITIES enumeration is used in the WDF_DEVICE_POWER_POLICY_IDLE_SETTINGS structure.

Examples

The following code examples show how to enable idle support for a USB device. In each case, the STATUS_POWER_STATE_INVALID return value means the bus driver has reported that the device cannot wake itself.

KMDF Example


WDF_DEVICE_POWER_POLICY_IDLE_SETTINGS_INIT(&idleSettings,
                                           IdleUsbSelectSuspend);
status = WdfDeviceAssignS0IdleSettings(device,
                                       &idleSettings);
if (status == STATUS_POWER_STATE_INVALID){
    //
    // The device probably does not support wake. 
    // It might support idle without wake.
    //
    idleSettings.IdleCaps = IdleCannotWakeFromS0;
    status = WdfDeviceAssignS0IdleSettings(device,
                                           &IdleSettings);
    if (!NT_SUCCESS(status) {...}
 }
else {...}

UMDF Example


hr = pIWDFDevice2->AssignS0IdleSettings(IdleUsbSelectSuspend,
                                        PowerDeviceD3,
                                        IDLEWAKE_TIMEOUT_MSEC,
                                        IdleAllowUserControl,
                                        WdfTrue);
if (hr == HRESULT_FROM_NT(STATUS_POWER_STATE_INVALID)){
    //
    // The device probably does not support wake. 
    // It might support idle without wake.
    //
    hr = pIWDFDevice2->AssignS0IdleSettings(IdleCannotWakeFromS0,
                                         PowerDeviceD3,
                                         IDLEWAKE_TIMEOUT_MSEC,
                                         IdleAllowUserControl,
                                         WdfTrue);
    if (!SUCCEEDED(hr)) {...}
}
else {...}

Requirements