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

• US 8,392,619 B2
• Filed: 02/10/2011
• Issued: 03/05/2013
• Est. Priority Date: 02/14/2008
• Status: Active Grant

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Casper, Daniel F., Bendyk, Mark P., Flanagan, John R., Huang, Catherine C., Kalos, Matthew J., Njoku, Ugochukwu C., Riedy, Dale F., Sittmann, Gustav E., Yudenfriend, Harry M.
• Primary Examiner(s): Lee, Chun-Kuan
• Assistant Examiner(s): Unelus, Ernest
• Application Number:
  US13/024,468
• Publication Number:
  US 20110131343A1
• Time in Patent Office: 754 Days
• Field of Search: 710/21, 710/35, 710/3, 710/4, 710/20, 711/1, 711/100, 711/101
• US Class Current: 710/3
• CPC Class Codes: G06F 12/1009 using page tables, e.g. page table structures
• CPC Class Codes: G06F 12/1036 for multiple virtual address spaces, e.g. segmentation G06F12/1045 takes precedence
• CPC Class Codes: G06F 13/124 where hardware is a sequential transfer control unit, e.g. microprocessor, peripheral processor or state-machine
• CPC Class Codes: G06F 2212/65 Details of virtual memory and virtual address translation
• CPC Class Codes: G06F 3/00 Input arrangements for transferring data to be processed into a form capable of being handled by the computer; Output arrangements for transferring data from processing unit to output unit, e.g. interface arrangements
• CPC Class Codes: G06F 3/0604 Improving or facilitating administration, e.g. storage management
• CPC Class Codes: G06F 3/0655 Vertical data movement, i.e. input-output transfer; data movement between one or more hosts and one or more storage devices
• CPC Class Codes: G06F 3/0673 Single storage device

Abstract

Systems, methods and computer program products for providing indirect data addressing at an I/O subsystem of an I/O processing system. The computer program product includes a tangible storage medium readable by a processing circuit and storing instructions for execution by the processing circuit for performing a method. The method includes receiving a control word for an I/O operation. The control word includes an indirect data address for data associated with the I/O operation. The indirect data address includes a starting location of a list of storage addresses that collectively specify the data, the list spans two or more non-contiguous storage locations. Data is gathered responsive to the list. The gathered data is transmitted to a control unit in the I/O processing system.

Claims

1. A non-transitory computer program product for providing indirect data addressing at an input/output (I/O) subsystem of an I/O processing system, the computer program product comprising:

a non-transitory 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 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;

forwarding a transport command control block (TCCB) from the channel subsystem to a control unit controlling an I/O device for executing the I/O operation, the TCCB including at least one device control word (DCW) and the TCCB being obtained by a location identified by a transport control word (TCW);

gathering the data, wherein gathering comprises accessing entries of the list until a last entry is accessed, wherein accessing includes

     1) and

     2);

1) based on an entry of the list comprising a not-set first flag and a corresponding first storage address, gathering data from a corresponding storage location; and

2) based on an entry of the list comprising a set first flag and a corresponding second storage address, obtaining a next entry of the list from a second storage location, wherein the second storage address is located contiguously to the first storage address when an entry of the list comprises the not-set first flag, and the second storage address is located non-contiguously to the first storage address when an entry of the list comprises the set first flag; and

transmitting the gathered data to the control unit in the I/O processing system.

2. The non-transitory computer program product of claim 1, wherein the list of storage addresses includes transport mode indirect data address words (TIDAWs), the first storage address refers to a portion of the data and the second storage address refers to the second storage location where additional storage addresses in the list are located.

3. The non-transitory computer program product of claim 1, wherein for each storage address on the list, the gathering includes:

based on an entry of the list comprising the not-set first flag, adding contents from the first storage address to the data; and

based on an entry of the list comprising the set first flag, accessing the second storage address and a second flag located at the second storage address, and adding contents from the second storage address to the data based on the second flag being a not-set second flag.

4. The non-transitory computer program product of claim 1, wherein the list further includes a count field associated with each storage address in the list, the count field indicating a number of bytes to read from the storage address and the gathering is based on the count fields and to the storage addresses.

5. The non-transitory computer program product of claim 1, wherein the control word includes the TCW, and the list of storage addresses is a transport indirect data address list (TIDAL).

6. The non-transitory computer program product of claim 1, wherein the I/O subsystem is a channel subsystem.

7. The non-transitory computer program product of claim 1, wherein the control word includes a flag to indicate that it includes an indirect data address.

8. The non-transitory computer program product of claim 1, wherein the method further comprises, based on an entry of the list comprising a set last entry flag, determining that the entry is a last entry to be accessed.

9. The non-transitory computer program product of claim 1, wherein the data includes at least one of control data and customer data.

22. The computer program product of claim 1, wherein the list includes a plurality of the entries, each of the plurality of the entries including a storage address and the flag.

10. 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 configured for 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;

forwarding a transport command control block (TCCB) from the channel subsystem to the control unit controlling an I/O device for executing the I/O operation, the TCCB including at least one device control word (DCW) and the TCCB being obtained by a location identified by the TCW;

gathering the data, wherein gathering comprises accessing entries of the list until a last entry is accessed, wherein accessing includes

     1) and

     2);

1) based on an entry of the list comprising a not-set first flag and a corresponding first storage address, gathering data from a corresponding storage location; and

2) based on an entry of the list comprising a set first flag and a corresponding second storage address, obtaining a next entry of the list from a second storage location, wherein the second storage address is located contiguously to the first storage address when an entry of the list comprises the not-set first flag, and the second storage address is located non-contiguously to the first storage address when an entry of the list comprises the set first flag; and

transmitting the gathered data to the control unit.

11. The apparatus of claim 10, wherein the list of storage addresses includes transport mode indirect data address words (TIDAWs), the first storage address refers to a portion of the data and the second storage address refers to the second storage location where additional storage addresses in the list are located.

12. The apparatus of claim 10, wherein for each storage address on the list, the gathering includes:

based on an entry of the list comprising the not-set first flag, adding contents from the first storage address to the data; and

based on an entry of the list comprising the set first flag, accessing the second storage address and a second flag located at the second storage address, and adding contents from the second storage address to the data based on the second flag being a not-set second flag.

13. The apparatus of claim 10, wherein the list further includes a count field associated with each storage address in the list, the count field indicating a number of bytes to read from the storage address and the gathering is based on the count fields and to the storage addresses.

14. The apparatus of claim 10, wherein the data includes one or both of control data and customer data.

15. The apparatus of claim 10, wherein the I/O subsystem is a channel subsystem that is included in a host system, and an I/O communications adapter in the channel subsystem is configured to communicate with the control unit via a fibre channel network using a FICON protocol.

23. The apparatus of claim 10, wherein the list includes a plurality of the entries, each of the plurality of the entries including a storage address and the flag.

16. 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;

forwarding a transport command control block (TCCB) from the channel subsystem to a control unit controlling an I/O device for executing the I/O operation, the TCCB including at least one device control word (DCW) and the TCCB being obtained by a location identified by the TCW;

gathering the data, wherein gathering comprises accessing entries of the list until a last entry is accessed, wherein accessing includes

     1) and

     2);

1) based on an entry of the list comprising a not-set first flag and a corresponding first storage address, gathering data from a corresponding storage location; and

2) based on an entry of the list comprising a set first flag and a corresponding second storage address, obtaining a next entry of the list from a second storage location, wherein the second storage address is located contiguously to the first storage address when an entry of the list comprises the not-set first flag, and the second storage address is located non-contiguously to the first storage address when an entry of the list comprises the set first flag;

transmitting the gathered data to the control unit in the I/O processing system.

17. The method of claim 16, wherein the list of storage addresses includes transport mode indirect data address words (TIDAWs), the first storage address refers to a portion of the data and the second storage address refers to the storage location where additional storage addresses in the list are located.

18. The method of claim 16, wherein for each storage address on the list, the gathering includes:

based on an entry of the list comprising the not-set first flag, adding contents from the first storage address to the data; and

based on an entry of the list comprising the set first flag, accessing the second storage address and a second flag located at the second storage address, and adding contents from the second storage address to the data based on the second flag being a not-set second flag.

19. The method of claim 16, wherein the list further includes a count field associated with each storage address in the list, the count field indicating a number of bytes to read from the storage address and the gathering is based on the count fields and to the storage addresses.

20. The method of claim 16, further comprising, based on an entry of the list comprising a set last entry flag, determining that the entry is a last entry to be accessed.

21. The method of claim 16, wherein the data includes at least one of control data and customer data.

24. The method of claim 16, wherein the list includes a plurality of the entries, each of the plurality of the entries including a storage address and the flag.