PROVIDING INDIRECT DATA ADDRESSING FOR A CONTROL BLOCK AT A CHANNEL SUBSYSTEM OF AN I/O PROCESSING SYSTEM

• US 20090210563A1
• Filed: 02/14/2008
• Published: 08/20/2009
• 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., Huang, Catherine C., Flanagan, John R., Sittmann, Gustav E., Njoku, Ugochukwu C., Casper, Daniel F., Riedy, Dale F.
• Granted Patent: US 8,117,347 B2
• Time in Patent Office: Days
• US Class Current: 710/5
• CPC Class Codes: G06F 13/126 and has means for transferring I/O instructions and statuses between control unit and main processor
• CPC Class Codes: G06F 13/385 for adaptation of a particular data processing system to different peripheral devices
• CPC Class Codes: G06F 3/061 Improving I/O performance
• CPC Class Codes: G06F 3/0659 Command handling arrangements, e.g. command buffers, queues, command scheduling

Abstract

An computer program product, apparatus, and method for facilitating input/output (I/O) processing for an I/O operation at a host computer system configured for communication with a control unit. 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 the host computer system obtaining a transport command word (TCW) for an I/O operation. The TCW specifies a location of one or more I/O commands and a flag. The flag is set to indicate that the location is an indirect address. The host computer system extracts the location of the one or more I/O commands and the flag from the TCW. The host computer system gathers the one or more I/O commands responsive to the location specified by the TCW and the flag, and then forwards the one or more I/O commands to the control unit for execution.

Claims

1. A computer program product for facilitating input/output (I/O) processing for an I/O operation at a host computer system configured for communication with a control unit, 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;

the host computer system obtaining a transport command word (TCW) for an I/O operation, the TCW specifying a location of one or more I/O commands and a flag, wherein the flag is set to indicate that the location is an indirect address;

the host computer system extracting the location of the one or more I/O commands and the flag from the TCW;

the host computer system gathering the one or more I/O commands responsive to the location specified by the TCW and the flag; and

the host computer system forwarding the one or more I/O commands to the control unit for execution.

2. The computer program product of claim 1 wherein the location includes a list of addresses, each address in the list containing a portion of the one or more I/O commands.

3. The computer program product of claim 2 wherein the location includes a transport indirect data address list (TIDAL).

4. The computer program product of claim 1 wherein the one or more I/O commands are included in a command control block and the location specified by the TCW is the location of the command control block.

5. The computer program product of claim 4 wherein the command control block further includes a header for specifying a format of the one or more I/O commands.

6. The computer program product of claim 4 wherein the command control block further includes a trailer for providing a check word and specifying the amount of data to transfer.

7. The computer program product of claim 1 wherein the one or more I/O commands include command codes and control data.

8. The computer program product of claim 1 wherein the TCW specifies a location of two or more I/O commands.

9. The computer program product of claim 1 wherein the host computer system includes a channel subsystem and the method is performed by the channel subsystem.

10. The computer program product of claim 1 wherein the TCW is obtained from a host operating system.

11. An apparatus for providing indirect data addressing for a control block at a host computer system configured for communication with a control unit, the host computer system performing:

obtaining a TCW for an I/O operation, the TCW specifying a location of one or more I/O commands and a flag, wherein the flag is set to indicate that the location is an indirect address;

extracting the location of the one or more I/O commands and the flag from the TCW;

gathering the one or more I/O commands responsive to the location specified by the TCW and the flag; and

forwarding the one or more I/O commands to the control unit for execution.

12. The apparatus of claim 11 wherein the location includes a list of addresses, each address in the list containing a portion of the one or more I/O commands.

13. The apparatus of claim 11 wherein the location includes a TIDAL.

14. The apparatus of claim 11 wherein the one or more I/O commands are included in a command control block and the location specified by the TCW is the location of the command control block.

15. The apparatus of claim 11 wherein the command control block further includes a header for specifying a format of the one or more I/O commands.

16. The apparatus of claim 11 wherein the command control block further includes a trailer for providing a check word and specifying the amount of data to transfer.

17. The apparatus of claim 11 wherein the one or more I/O commands include command codes and control data.

18. The apparatus of claim 11 wherein the TCW specifies two or more I/O commands.

19. A method for providing indirect data addressing for a control block at a host computer system configured for communication with a control unit, the method comprising:

obtaining a TCW for an I/O operation, the TCW specifying a location of one or more I/O commands and a flag, wherein the flag is set to indicate that the location is an indirect address;

extracting the location of the one or more I/O commands and the flag from the TCW;

gathering the one or more I/O commands responsive to the location specified by the TCW and the flag; and

forwarding the one or more I/O commands to the control unit for execution.

20. The method of claim 19 wherein the location includes a list of addresses, each address in the list containing a portion of the one or more I/O commands.

21. The method of claim 19 wherein the one or more I/O commands are included in a command control block and the location specified by the TCW is the location of the command control block.

22. The method of claim 21 wherein the command control block further includes a trailer to provide a check word and specifying the amount of data to transfer.

23. The method of claim 19 wherein the one or more I/O commands include command codes and control data.

24. The method of claim 19 wherein the host computer includes a channel subsystem and the method is performed by the channel subsystem.

25. The method of claim 19 wherein the TCW is obtained from a host operating system.