PROVIDING INDIRECT DATA ADDRESSING IN AN INPUT/OUTPUT PROCESSING SYSTEM WHERE THE INDIRECT DATA ADDRESS LIST IS NON-CONTIGUOUS

• US 20110131343A1
• Filed: 02/10/2011
• Published: 06/02/2011
• Est. Priority Date: 02/14/2008
• Status: Active Grant

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Kalos, Matthew J., Yudenfriend, Harry M., Huang, Catherine C., Flanagan, John R., Bendyk, Mark P., Sittmann, Gustav E., Njoku, Ugochukwu C., Casper, Daniel F., Riedy, Dale F.
• Granted Patent: US 8,392,619 B2
• Time in Patent Office: Days
• US Class Current: 710/4
• 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 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 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;

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 a 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 a 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 a control unit in the I/O processing system.

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

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

responsive to 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 in response to the second flag being a not-set second flag.

4. The computer program product of claim 1 wherein the second storage address in the list 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.

5. The 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 responsive to the count fields and to the storage addresses.

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

7. The computer program product of claim 1 wherein the I/O subsystem is a channel subsystem.

8. The computer program product of claim 1 wherein the control word includes a flag to indicate that it includes an indirect data address.

9. The computer program product of claim 1 wherein the method further comprises, responsive to an entry of the list comprising a set last entry flag, determining that the entry is a last entry to be accessed.

10. The computer program product of claim 1 wherein the data includes at least one of control data and customer data.

11. 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;

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 a 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 a 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.

12. The apparatus of claim 11 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.

13. The apparatus of claim 11 wherein for each storage address on the list, the gathering includes:

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

responsive to 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 in response to the second flag being a not-set second flag.

14. The apparatus of claim 11 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.

15. The apparatus of claim 11 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 responsive to the count fields and to the storage addresses.

16. The apparatus of claim 11 wherein the data includes one or both of control data and customer data.

17. The apparatus of claim 11 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 adapted to communicate with the control unit via a fibre channel network using a FICON protocol.

18. 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;

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 a 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 a 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.

19. The method of claim 18 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.

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

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

responsive to 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 in response to the second flag being a not-set second flag.

21. The method of claim 18 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.

22. The method of claim 18 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 responsive to the count fields and to the storage addresses.

23. The method of claim 18 further comprising, responsive to an entry of the list comprising a set last entry flag, determining that the entry is a last entry to be accessed.

24. The method of claim 18 wherein the data includes at least one of control data and customer data.

25. 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;

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;

i) responsive to an entry of the list comprising a not-set first flag and a corresponding first storage address, a first storage location corresponding to the corresponding first storage address; and

i) responsive to an entry of the list comprising a 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.