Power and resource management are key goals for the success of modern battery-supplied multimedia devices. This kind of devices are usually based on SoCs with a wide range of subsystems, that compete in the usage of shared resources, and offer several power saving capabilities, but need an adequate software support to exploit such capabilities. In this paper we present Constrained Power Management (CPM), a cross-layer formal model and framework for power and resource management, targeted to MPSoC-based devices. CPM allows coordination and communication, among applications and device drivers, to reduce energy consumption without compromising QoS. A dynamic and multiobjective optimization strategy is supported, which has been designed to have a negligible overhead on the development process and at run-time.