Apart from hardware and software-specific failures, failures arising from hardware-software interaction causes notorious system failures. Researches have reported two types of interaction failures in a system: hardwaredriven software failure and software-driven hardware failure. An efficient reliability prediction approaches must consider all types of interactions. We critically analyse the existing reliability prediction models for the combined hardware-software system. We also propose a comparison framework to evaluate the existing reliability models for combined hardware-software systems. The results of our study suggest that none of the considered approaches completely satisfy the characteristics of a good reliability prediction model. Existing approaches hardly consider all types of hardware-software interactions. They also fail to consider reliability aspects of distributed systems where a system interacts with external devices. Our proposed comparison framework can be used as a benchmark to construct an efficient reliability prediction model for combined hardware-software systems.