EFI_USBFN_IO_PROTOCOL.Transfer

Article
03/23/2023

The Transfer function handles transferring data to or from the host on the specified endpoint.

Direction	Description
EfiUsbEndpointDirectionDeviceTx	Start a transmit transfer on the specified endpoint and return immediately.
EfiUsbEndpointDirectionDeviceRx	Start a receive transfer on the specified endpoint and return immediately with available data.

Syntax

typedef
EFI_STATUS
(EFIAPI *EFI_USBFN_IO_TRANSFER) (
  IN EFI_USBFN_IO_PROTOCOL         *This,
  IN UINT8                         EndpointIndex,
  IN EFI_USBFN_ENDPOINT_DIRECTION  Direction,
  IN OUT UINTN                     *BufferSize,
  IN OUT VOID                      *Buffer
  );

Parameters

This
A pointer to the EFI_USBFN_IO_PROTOCOL instance.

EndpointIndex
Indicates the endpoint on which TX or RX transfer needs to take place.

Direction
Direction of the endpoint. For more information, see EFI_USBFN_ENDPOINT_DIRECTION.

BufferSize
If Direction is EfiUsbEndpointDirectionDeviceRx: On input, the size of the buffer in bytes. On output, the amount of data returned in the buffer in bytes. If Direction is EfiUsbEndpointDirectionDeviceTx: On input, the size of the Buffer in bytes. On output, the amount of data actually transmitted in bytes.

Buffer
If Direction is EfiUsbEndpointDirectionDeviceRx:The buffer to return the received data. If Direction is EfiUsbEndpointDirectionDeviceTx: The buffer that contains the data to be transmitted.

This buffer is allocated and freed by using the AllocateTransferBuffer and FreeTransferBuffer functions. The caller of this function must not free or reuse the buffer until an EfiUsbMsgEndpointStatusChangedRx or EfiUsbMsgEndpointStatusChangedTx message was received along with the address of the transfer buffer as part of the message payload. See EFI_USBFN_IO_PROTOCOL.EventHandler for more information on various messages and their payloads.

Return values

The function returns one of the following values:

Return code	Description
EFI_SUCCESS	The function returned successfully
EFI_INVALID_PARAMETER	A parameter is invalid
EFI_DEVICE_ERROR	The physical device reported an error.
EFI_NOT_READY	The physical device is busy or not ready to process this request

Remarks

A class driver must call EFI_USBFN_IO_PROTOCOL.EventHandler repeatedly to receive updates on the transfer status and number of bytes transferred on various endpoints. Upon update on transfer status, the Buffer field of the EFI_USBFN_TRANSFER_RESULT structure must be initialized with the Buffer pointer that was supplied to this method. This function fails with EFI_INVALID_PARAMETER return code if the specified direction is incorrect for the endpoint.

The overview of the call sequence is illustrated in UEFI Sequence Diagram.

This function fails with EFI_INVALID_PARAMETER return code if the specified direction is incorrect for the endpoint.

Requirements

Header: User generated

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