Intel Extensible Firmware Interface - Manual (Page 563)

Protocols — USB Support
Version 1.10 12/01/02 14-23
EFI_USB_HC_PROTOCOL.AsyncIsochronousTransfer()
Summary
Submits nonblocking isochronous transfer to an isochronous endpoint of a USB device.
Prototype
typedef
EFI_STATUS
(EFIAPI * EFI_USB_HC_PROTOCOL_ASYNC_ISOCHRONOUS_TRANSFER) (
IN EFI_USB_HC_PROTOCOL
*This,
IN UINT8 DeviceAddress,
IN UINT8 EndPointAddress,
IN UINT8 MaximumPacketLength,
IN OUT VOID *Data,
IN UINTN DataLength,
IN EFI_ASYNC_USB_TRANSFER_CALLBACK IsochronousCallBack,
IN VOID *Context OPTIONAL
);
Parameters
This A pointer to the EFI_USB_HC_PROTOCOL instance. Type
EFI_USB_HC_PROTOCOL is defined in Section 14.1.
DeviceAddress Represents the address of the target device on the USB, which is
assigned during USB enumeration.
EndPointAddress The combination of an endpoint number and an endpoint
direction of the target USB device. Each endpoint address
supports data transfer in one direction except the control
endpoint (whose default endpoint address is zero). It is the
caller’s responsibility to make sure that the
EndPointAddress represents an isochronous endpoint.
MaximumPacketLength Indicates the maximum packet size the target endpoint is capable
of sending or receiving. For isochronous endpoints, this value is
used to reserve the bus time in the schedule, required for the per-
frame data payloads. The pipe may, on an ongoing basis,
actually use less bandwidth than that reserved.
Data A pointer to the buffer of data that will be transmitted to USB
device or received from USB device.
DataLength Specifies the length, in bytes, of the data to be sent to or received
from the USB device.