This IOCTL is no longer supported. It is available to keep backward compatibility with older interface library and application.
For more information on USB transfer size please refer link from Microsoft : http://msdn.microsoft.com/en-us/library/ff538112.aspx
Following are the maximum transfer size limits set into the CyUSB3.sys driver for various transfers.
1. Bulk and Interrupt Transfer
2. Full Speed Isochronous Transfer
3. High Speed and Super Speed Isochronous Transfer