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

An apparatus for providing indirect data addressing at an I/O subsystem of an I/O processing system, the apparatus comprising:

• an I/O subsystem adapted to communication with a control unit in the I/O processing system, the I/O subsystem configured to perform a method comprising:
• receiving a control word for an I/O operation, the control word including an indirect data address for data associated with the I/O operation, the indirect data address including a starting location of a list of storage addresses that collectively specify the data, wherein two successive list entries are located contiguously when a first of said two successive entries comprises a not-set first flag and are located non-contiguously when the first of said two successive entries comprises a set first flag;
• gathering the data, wherein gathering comprises accessing entries of the list until a last entry is accessed, wherein accessing includes 1) and 2):
• 1) responsive to an entry of the list comprising, the not-set first flag and a corresponding first storage address, gathering data from a corresponding storage location;
• and
• 2) responsive to an entry of the list comprising, the set first flag and a corresponding second storage address, obtaining a next entry of the list from a second storage location;
• and transmitting the gathered data to the control unit.

A method for providing indirect data addressing at an I/O subsystem of an I/O processing system, the method comprising:

• receiving a control word for an I/O operation at the I/O subsystem, the control word including an indirect data address for data associated with the I/O operation, the indirect data address including a starting location of a list of storage addresses that collectively specify the data, wherein two successive list entries are located contiguously when a first of said two successive entries comprises a not-set first flag and are located non-contiguously when the first of said two successive entries comprises a set first flag;
• gathering the data, wherein gathering comprises accessing entries of the list until a last entry is accessed, wherein accessing includes 1) and 2):
• 1) responsive to an entry of the list comprising, the not-set first flag and a corresponding first storage address, gathering data from a corresponding storage location;
• and
• 2) responsive to an entry of the list comprising, the set first flag and a corresponding second storage address, obtaining a next entry of the list from a second storage location;
• transmitting the gathered data to a control unit in the I/O processing system.

A computer program product for providing indirect data addressing at an I/O subsystem of an I/O processing system, the computer program product comprising:

• a tangible storage medium readable by a processing circuit and storing instructions for execution by the processing circuit for performing a method comprising:
• receiving a control word for an I/O operation, the control word including an indirect data address for customer data output from the I/O operation, the indirect data address including a starting location of a list of storage addresses in the form of transport mode indirect data address words (TIDAWs) that collectively specify a storage location for the customer data output, wherein two successive TIDAWs are located contiguously when a first of said two successive entries comprises a not-set first flag and are located non-contiguously contiguously when the first of said two successive entries comprises a set first flag;
• receiving the customer data output from a control unit in the I/O processing system in response to the I/O operation being executed at the control unit;
• and
• storing the customer data output at the storage location at the I/O subsystem responsive to the list, wherein the storage location includes at least one of:
• 1) responsive to an entry of the list comprising, the not-set first flag and a corresponding first storage address, a first storage location corresponding to the corresponding first storage address;
• and
• 2) responsive to an entry of the list comprising, the set first flag and a corresponding second storage address, a second storage location specified by a next entry of the list obtainable from a storage location corresponding to the corresponding second storage address.

A method for providing indirect data addressing at an I/O subsystem of an I/O processing system, the method comprising:

• receiving a control word for an I/O operation, the control word including an indirect data address for customer data output from the I/O operation, the indirect data address including a starting location of a list of storage addresses in the form of transport mode indirect data address words (TIDAWs) that collectively specify a storage location for the customer data output, wherein two successive TIDAWs are located contiguously when a first of said two successive entries comprises a not-set first flag and are located non-contiguously when the first of said two successive entries comprises a set first flag;
• receiving the customer data output from a control unit in the I/O processing system in response to the I/O operation being executed at the control unit;
• and
• storing the customer data output at the storage location at the I/O subsystem responsive to the list, wherein the storage location includes at least one of:
• 1) responsive to an entry of the list comprising, the not-set first flag and a corresponding first storage address, a first storage location corresponding to the corresponding first storage address;
• and
• 2) responsive to an entry of the list comprising, the set first flag and a corresponding second storage address, a second storage location specified by a next entry of the list obtainable from a storage location corresponding to the corresponding second storage address.

An apparatus for providing indirect data addressing at an I/O subsystem of an I/O processing system, the apparatus comprising:

• an I/O subsystem adapted to communication with a control unit in the I/O processing system, the I/O subsystem configured to perform a method comprising:
• receiving a control word for an I/O operation, the control word including an indirect data address for customer data output from the I/O operation, the indirect data address including a starting location of a list of storage addresses in the form of transport mode indirect data address words (TIDAWs) that collectively specify a storage location for the customer data output, wherein two successive TIDAWs are located contiguously when a first of said two successive entries comprises a not-set first flag and are located non-contiguously when the first of said two successive entries comprises a set first flag;
• receiving the customer data output from a control unit in the I/O processing system in response to the I/O operation being executed at the control unit;
• and
• storing the customer data output at the storage location at the I/O subsystem responsive to the list, wherein the storage location includes at least one of:
• 1) responsive to an entry of the list comprising, the not-set first flag and a corresponding first storage address, a first storage location corresponding to the corresponding first storage address;
• and
• 2) responsive to an entry of the list comprising, the set first flag and a corresponding second storage address, a second storage location specified by a next entry of the list obtainable from a storage location corresponding to the corresponding second storage address.