IWDFUsbTargetDevice::RetrievePowerPolicy method

The RetrievePowerPolicy method retrieves a WinUsb power policy.

Syntax


HRESULT RetrievePowerPolicy(
  [in]       ULONG PolicyType,
  [in, out]  ULONG *ValueLength,
  [out]      PVOID Value
);

Parameters

PolicyType [in]: The type of WinUsb power policy that the UMDF driver requests.
ValueLength [in, out]: A pointer to a variable that, on input, contains the size, in bytes, of the buffer that RetrievePowerPolicy supplies in Value. On output, this parameter contains the size that RetrievePowerPolicy requires for Value.
Value [out]: A pointer that receives the buffer that contains the WinUsb power policy.

Return value

RetrievePowerPolicy returns one of the following values:

Return code	Description
S_OK	RetrievePowerPolicy successfully retrieved the WinUsb power policy.
E_OUTOFMEMORY	RetrievePowerPolicy encountered an allocation failure.
An error code that is defined in Winerror.h	This value corresponds to the error code that the WinUsb API returned.

Remarks

Power policy controls the power management that WinUsb for the device performs.

For information about valid policy types that a UMDF driver can pass for the PolicyType parameter and values that the framework returns, see the WinUsb_GetPowerPolicy function.

For more information about the power behavior of WinUSB, see WinUSB Power Management.

The RetrievePowerPolicy method generates a UMDF request and synchronously sends the request to the I/O target.

Requirements