The role of the device driver is to pass information between the operating system and the adapter device driver by accepting I/O requests and passing these requests to the adapter device driver. The device driver should accept either character or block I/O requests, build the necessary commands, and then issue these commands to the device through the adapter device driver.
The device driver should also process the various required reservations and releases needed for the device. The device driver is notified through the iodone kernel service once the adapter has completed the processing of the command. The device driver should then notify its calling process that the request has completed processing through the iodone kernel service.