Writing Tightly Coupled Drivers
Unlike layered and filter drivers, tightly coupled drivers do not use the I/O Manager's IoCallDriver function to communicate with each other. Indeed, tightly coupled drivers do not need to conform to the strict stacking architecture that the WDM model constructs. Instead, they define a private calling interface. The advantage of this approach is that it is usually faster than the IRP passing model supported by the I/O Manager. In trade for improved performance, the mechanics of the interface between tightly coupled drivers is left as an implementation detail. As a result, it is difficult for tightly coupled drivers from different vendors to interoperate.
How Tightly Coupled Drivers Work
Since the interface between ...