Common Driver Interface
The Common Driver Interface is a German project made by the people behind Tyndur, a community project of LowLevel, the German equivalent of the OSDev wiki. The interface offers less functionality than UDI but is a lot easier to implement. The creators have also implemented the interface in their own OS and they have made a nice amount of drivers. If you noticed I'm not talking about EDI, it is because EDI is dead.
The source can be found at http://lpt.tyndur.org/cdi/english/. You can find the sources in Resources. You just need to clone the git repository. This will give you the drivers and the header files. The header files are in the include folder.