An apparatus, comprising: one or more processor cores to execute an operating system - OS - with a power management framework - OSPM -; and a power management unit - PMU -; characterised by: a direct power management interface - DPMI - coupled to the PMU and arranged to communicate power state messages directly between the PMU and a plurality of different devices, and to process power state change request messages from said devices without involvement of the OS and its power management framework, the PMU to control the amount of power supplied to the devices, wherein the PMU is arranged to: check if there is a power state change request received by the DPMI from a first device of said devices, if there is a request received by the DPMI, determine if there is an OSPM power state request with a higher priority, based on a predetermined policy, than the request received by the DPMI, if it is determined that there is a OSPM power state request with a higher priority, the OSPM power state request is fulfilled, and if it is determined that the DPMI power state request carries a higher priority, process the DPMI power state request, wherein the PMU is arranged to execute power state changes outside of the OS power management framework. one or more processor cores to execute an operating system - OS - with a power management framework - OSPM -; and a power management unit - PMU -; characterised by: a direct power management interface - DPMI - coupled to the PMU and arranged to communicate power state messages directly between the PMU and a plurality of different devices, and to process power state change request messages from said devices without involvement of the OS and its power management framework, the PMU to control the amount of power supplied to the devices, wherein the PMU is arranged to: check if there is a power state change request received by the DPMI from a first device of said devices, if there is a request received by the DPMI, determine if there is an OSPM power state request with a higher priority, based on a predetermined policy, than the request received by the DPMI, if it is determined that there is a OSPM power state request with a higher priority, the OSPM power state request is fulfilled, and if it is determined that the DPMI power state request carries a higher priority, process the DPMI power state request, wherein the PMU is arranged to execute power state changes outside of the OS power management framework. a direct power management interface - DPMI - coupled to the PMU and arranged to communicate power state messages directly between the PMU and a plurality of different devices, and to process power state change request messages from said devices without involvement of the OS and its power management framework, the PMU to control the amount of power supplied to the devices, wherein the PMU is arranged to: check if there is a power state change request received by the DPMI from a first device of said devices, if there is a request received by the DPMI, determine if there is an OSPM power state request with a higher priority, based on a predetermined policy, than the request received by the DPMI, if it is determined that there is a OSPM power state request with a higher priority, the OSPM power state request is fulfilled, and if it is determined that the DPMI power state request carries a higher priority, process the DPMI power state request, wherein the PMU is arranged to execute power state changes outside of the OS power management framework. check if there is a power state change request received by the DPMI from a first device of said devices, if there is a request received by the DPMI, determine if there is an OSPM power state request with a higher priority, based on a predetermined policy, than the request received by the DPMI, if it is determined that there is a OSPM power state request with a higher priority, the OSPM power state request is fulfilled, and if it is determined that the DPMI power state request carries a higher priority, process the DPMI power state request, determine if there is an OSPM power state request with a higher priority, based on a predetermined policy, than the request received by the DPMI, if it is determined that there is a OSPM power state request with a higher priority, the OSPM power state request is fulfilled, and if it is determined that the DPMI power state request carries a higher priority, process the DPMI power state request, if it is determined that there is a OSPM power state request with a higher priority, the OSPM power state request is fulfilled, and if it is determined that the DPMI power state request carries a higher priority, process the DPMI power state request, wherein the PMU is arranged to execute power state changes outside of the OS power management framework.