A computer system having a host coupled to a storage device via a peripheral component interconnect express bus. The host communicates with the storage device in accordance with a non-volatile memory host controller interface specification. The host provides a customized module containing instructions for performing the operations of a customized command. The host sends an idle time command to the storage device for execution at an idle time. In response to a determination that the storage device is in an idle state, the storage device executes the idle time command, during which the module may be used by the controller of the storage device.