Synthesizing Operating System Based Device Drivers in Embedded Systems

This paper presents a correct-by-construction synthesis method for generating operating system based device drivers from a formally specified device behavior model. Existing driver development is largely manual using an ad-hoc design methodology. Consequently, this task is error prone and becomes a bottleneck in embedded system design methodology. Our solution to this problem starts by accurately specifying device access behavior with a formal model, viz. extended event driven finite state machines. We state easy to check soundness conditions on the model that subsequently guarantee properties such as bounded execution time and deadlock-free behavior. We design a deadlock-free resource accessing scheme for our device access model. Finally, we synthesize an operating system (OS) based event processing mechanism, which is the core of the device driver, using a disciplined methodology that assures the correctness of the resulting driver. We validate our synthesis method using two case studies: an infrared port and the USB device controller for an SA 1100 based handheld. Besides assuring a correct-by -construction driver, the size of the specification is 70% smaller than a manually written driver, which is a strong indicator of improved design productivity.