3.1.4.1.1 Datatype Name Parameters
pDatatype: This parameter MUST be one of the following:
NULL, to indicate that the default data type for the printer MUST be used.
A pointer to a string that specifies the data type to be associated with the printer handle.
For rules governing data type names, see section 2.2.4.2.
The individual method sections include the following parameter validation steps by reference:
If pDatatype is not NULL, verify that the string that is referenced by the pDatatype parameter identifies one of the data types that the printer or print server supports, and if that verification fails, return ERROR_INVALID_DATATYPE.
Note: A client SHOULD use RpcEnumPrintProcessorDatatypes (section 3.1.4.8.5), specifying a print processor, to obtain a list of supported data types.