1. A computer program product for enabling adapters in a computing environment, said computer program product comprising: a non-transitory computer readable storage medium readable by a processing circuit and storing instructions for execution by the processing circuit for performing a method comprising: based on executing a Call Logical Processor (CLP) instruction for enabling an adapter, the CLP instruction comprising a function handle and requesting a number of direct memory access (DMA) address spaces to be assigned to the adapter, a DMA address space being a particular portion of system memory to be assigned to the adapter, and the function handle configured: to be used by the operating system to identify the adapter; to be used in selecting a function table entry associated with the adapter; and to have an adapter not enabled indicator, and the execution enabling one or more DMA address spaces comprising a) and b): a) enabling the adapter, the enabling comprising enabling registration for address translation and interruptions for supporting direct memory accesses and message signaled interruptions for the adapter, the enabling comprising: using the function handle of the adapter to locate the function table entry associated with the adapter; and employing information in the function table entry to determine the adapter is to be enabled; and b) returning the function handle having an adapter enabled indicator.