LPCLEAR_FEATURE (Windows Embedded CE 6.0)

1/6/2010

This function sends a CLEAR_FEATURE request to a universal serial bus (USB) device.

Syntax

typedef USB_TRANSFER (* LPCLEAR_FEATURE)(
  USB_HANDLE hDevice,
  LPTRANSFER_NOTIFY_ROUTINE lpStartAddress,
  LPVOID lpvNotifyParameter,
  DWORD dwFlags,
  WORD wFeature,
  UCHAR bIndex
);

Parameters

• hDevice
  [in] Handle to a USB device.

• lpStartAddress
  [in] Pointer to the address, which might be NULL, of a callback routine of type LPTRANSFER_NOTIFY_ROUTINE.

• lpvNotifyParameter
  [in] Pointer to the parameter to pass to a callback routine.

• dwFlags
  [in] Value of USB_NO_WAIT or zero (0) and one of the values from the following table.

  Value	Description
  USB_SEND_TO_DEVICE	Request for device
  USB_SEND_TO_INTERFACE	Request for interface
  USB_SEND_TO_ENDPOINT	Request for endpoint

• wFeature
  [in] Feature selector. One of USB_FEATURE_* declared in the USB100.h header file.

• bIndex
  [in] Value of zero (0) for DEVICE or the interface or endpoint number.

Return Value

A USB_TRANSFER handle indicates success. NULL indicates failure.

Remarks

This function, like all other USB driver interface functions, is not directly accessible by any client drivers. Invoke it by dereferencing the lpClearFeature member of the USB_FUNCS structure passed to the client driver in the invocation of its USBDeviceAttach function.

This function initiates a control transfer to a USB device requesting that a specified feature be disabled. The Universal Serial Bus Specification defines features and appropriate feature request recipients. There is no facility for class-specific or vendor-specific feature selectors; vendors who need to implement non-standard operations should use vendor-specific requests rather than the standard requests.

Successful return from this function indicates that the request was issued to the device, or queued for issuing if USB_NO_WAIT was set; it does not mean that the feature was actually cleared. You must wait for and check the transfer completion status to determine whether or not the device was able to clear the feature.

Requirements

See Also

Reference

USB Host Driver Functions
GetTransferStatus
LPABORT_TRANSFER
LPIS_TRANSFER_COMPLETE
LPTRANSFER_NOTIFY_ROUTINE
LPSET_FEATURE
USB_FUNCS
USBDeviceAttach