Interface control process between using programs and shared hardware facilities

A method of structuring a session interface between a software operating system (OS) operating in privileged state and a using program operating in a non-privileged state for enabling a session of direct control by the using program over an asynchronous hardware facility (AHF) in a computing system controlled by the privileged OS, the method comprising steps of:

• initiating the session by transferring a request by the non-privileged using program to the OS for the OS to set up a direct communication facility between the using program and the AHF, the request containing locating information for locating a work request list (WRL) in an address space of the using program,
• structuring the direct communication facility by the OS allocating an active session table (AST) in a hardware system area (HSA) in system storage accessible to the OS and to an AHF processor of the AHF, the AST being structured with an AST section for each using program requesting a session with the AHF, writing by the OS into an AST section associated with a respective using program of WRL address information for enabling the AHF to access the WRL, the WRL being accessible to the respective using program but the HSA, the AST and the AST section not being accessible by the respective using program,
• storing by the using program of any number of AHF work requests in the WRL accessible to the using program,
• scanning by an AHF processor of the AST section for locating the WRL of an associated using program when the AHF processor is not executing a work request,
• executing by the AHF processor of any AHF work request found in the WRL during the scanning step, and
• posting by the AHF processor in the WRL of a completion indication when the AHF has completed work specified in the AHF work request performed by the executing step to directly provide the using program with an indication of availability of AHF work results without intervention by the OS in user request or AHF work completion communications between the AHF and the using program during the session.