Control Block Address Resolution: Keyword=addr or (reg)

You, as the caller, either define or reference the control blocks needed by CVAF filter. Caller-defined control blocks are: BUFLIST, CVPL, and FCL. Caller-referenced control blocks are: DEB, FLTAREA, IOAREA, and UCB. The CVAFFILT macro generates different instructions for keyword=addr and keyword=(reg) depending upon whether you are specifying a defined or referenced control block.

When you specify any control block's address as (reg), the CVAFFILT macro assumes that the register specified contains that address.
When you specify a "defined" control block's address as addr, the CVAFFILT macro assumes that the specified location is that of the control block itself. The macro generates a load address instruction (LA) to obtain the control block's address.
When you specify a "referenced" control block's address as addr, the CVAFFILT macro assumes that the specified location is that of a word containing the address of the control block. The macro generates a load instruction (L) to obtain the control block's address.