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Providing indirect data addressing in an input/output processing system where the indirect data address list is non-contiguous

  • US 9,720,844 B2
  • Filed: 08/04/2016
  • Issued: 08/01/2017
  • Est. Priority Date: 02/14/2008
  • Status: Active Grant
First Claim
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1. A computer program product for processing input/output (I/O) data at an I/O subsystem of an I/O processing system, the computer program product comprising:

  • a computer readable storage medium having program instructions embodied therewith, wherein the computer readable storage medium is not a transitory signal per se, the program instructions executable by a processing circuit to perform a method comprising;

    receiving a transport control word (TCW) at the I/O subsystem for an I/O operation, the TCW including an indirect data address for data associated with the I/O operation, the indirect data address including a starting location of a transport mode indirect data address list (TIDAL) of storage addresses that collectively specify the data, the TIDAL including a plurality of entries configured as transport mode indirect data address words (TIDAWs);

    gathering the data, wherein gathering comprises accessing an entry of the TIDAL, the entry located at an entry storage location and including an address, wherein accessing includes

         1) and

         2);

    1) based on the entry of the TIDAL indicating that the address is a data address, gathering data from a data storage location corresponding to the data address, and accessing a next entry of the TIDAL; and

    2) based on the entry of the TIDAL indicating that the address is an address of a next entry of the TIDAL, obtaining the next entry of the TIDAL from another storage location that is located non-contiguously to the entry storage location; and

    transmitting gathered data to a control unit in the I/O processing system, the control unit configured to control an I/O device for executing the I/O operation.

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