OpenBSD Hardware Sensors — Environmental Monitoring and Fan Control

Abstract

This thesis discusses the motivation, origin, history, design guidelines, API, the device drivers and userland utilities of the hardware sensors framework available in OpenBSD. The framework spans multiple utilities in the base system and the ports tree, is utilised by over 75 drivers, and is considered to be a distinctive and ready-to-use feature that sets OpenBSD apart from many other operating systems, and in its root is inseparable from the OpenBSD experience.

The present framework, however, is missing the functionality that would allow the user to interface with the fan-controlling part of the hardware monitors. We therefore discuss the topic of fan control and introduce sysctl-based interfacing with the fan-controlling capabilities of microprocessor system hardware monitors. The discussed prototype implementation reduces the noise and power-consumption characteristics in fans of personal computers, especially of those PCs that are designed from off-the-shelf components. We further argue that our prototype is easier, more intuitive and robust compared to solutions available elsewhere.