Responsibilities of the Adapter Device Driver

The adapter device driver is the software interface to the system hardware. This hardware includes the transport layer hardware, plus any other system I/O hardware required to run an I/O request. The adapter device driver hides the details of the I/O hardware from the device driver. The design of the software interface lets a user with limited knowledge of the system hardware write the upper device driver.

The adapter device driver manages the transport layer but not the devices. It can send and receive commands, but it cannot interpret the contents of the command. The lower driver also provides recovery and logging for errors related to the transport layer and system I/O hardware. Management of the device specifics is left to the device driver. The interface of the two drivers supports communication between the upper driver and the different transport layer adapters without requiring special code paths for each adapter.