IWDFUsbTargetDevice::RetrievePowerPolicy method (wudfusb.h)
[Warning: UMDF 2 is the latest version of UMDF and supersedes UMDF 1. All new UMDF drivers should be written using UMDF 2. No new features are being added to UMDF 1 and there is limited support for UMDF 1 on newer versions of Windows 10. Universal Windows drivers must use UMDF 2. For more info, see Getting Started with UMDF.]
The RetrievePowerPolicy method retrieves a WinUsb power policy.
Syntax
HRESULT RetrievePowerPolicy(
[in] ULONG PolicyType,
[in, out] ULONG *ValueLength,
[out] PVOID Value
);
Parameters
[in] PolicyType
The type of WinUsb power policy that the UMDF driver requests.
[in, out] ValueLength
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.
[out] Value
A pointer that receives the buffer that contains the WinUsb power policy.
Return value
RetrievePowerPolicy returns one of the following values:
| Return code | Description |
|---|---|
|
RetrievePowerPolicy successfully retrieved the WinUsb power policy. |
|
RetrievePowerPolicy encountered an allocation failure. |
|
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
| Requirement | Value |
|---|---|
| End of support | Unavailable in UMDF 2.0 and later. |
| Target Platform | Desktop |
| Minimum UMDF version | 1.5 |
| Header | wudfusb.h (include Wudfusb.h) |
| DLL | WUDFx.dll |