How does XFS find WFPOpen?

I am going to implement SPI for my own hardware (maybe virtual). As I found (maybe I'm wrong), when the application calls WFSOpen, XFS calls WFPOpen in the SPI. But that "in SPI" means where? Maybe I should point to the address of the dll file where WFPOpen is located somewhere in the registry. I also think the dll path should be in HKLM \ XFS \ Service_Provider \\ DllName. Is that enough? Is XFS sensitive to this path and registry key and uses it to find where the SPI is located? I did the above but I am getting WFS_ERR_SERVICE_NOT_FOUND. It seems that XFS is not looking for a function in the dll. What could be wrong?

I thought it would be better to send an xfs log so you can handle the problem. https://www.dropbox.com/s/6wwbjfpxxibjnl1/9603071652%20-%20XFSTrace.7z?dl=0