Providing indirect data addressing for a control block at a channel subsystem of an I/O processing system

• US 8,516,161 B2
• Filed: 01/16/2012
• Issued: 08/20/2013
• Est. Priority Date: 02/14/2008
• Status: Active Grant

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Flanagan, John R., Casper, Daniel F., Kalos, Matthew J., Riedy, Dale F., Sittmann, Gustav E., Njoku, Ugochukwu C., Huang, Catherine C.
• Primary Examiner(s): Tsai, Henry
• Assistant Examiner(s): Hassan, Aurangzeb
• Application Number:
  US13/351,073
• Publication Number:
  US 20120117275A1
• Time in Patent Office: 582 Days
• Field of Search: None
• 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 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, 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;

obtaining a transport command word (TCW) for an I/O operation, the TCW specifying a location address and a flag, the flag indicating whether the TCW directly or indirectly addresses a message for transmitting one or more commands to the control unit;

extracting the specified location address and the flag from the TCW;

obtaining the message from the specified location address based on the flag having a first value indicating direct addressing, the message comprising one or more I/O commands;

gathering one or more I/O commands from command locations specified by a list of addresses identified by the specified location address to form the message based on the flag having a second value indicating indirect addressing, the message comprising the gathered one or more I/O commands; and

forwarding the message to the control unit for execution.

2. The computer program product of claim 1 wherein the list of addresses comprises two or more I/O commands, and the forwarded message comprises the two or more I/O commands.

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

4. The computer program product of claim 3 wherein the TCCB further includes a header and a variable length transport control area, the header comprising information about the variable length transport control area, the variable length transport control area comprising one or more I/O commands, the header configured to specify a format of at least one of the one or more I/O commands and the gathered one or more I/O commands.

5. The computer program product of claim 3 wherein the TCCB further includes a trailer for providing a check word and specifying the amount of data to transfer.

6. The computer program product of claim 1 wherein at least one of the one or more I/O commands and the gathered one or more I/O commands includes command codes and control data.

7. 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.

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

9. 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 address and a flag, the flag indicating whether the TCW directly or indirectly addresses a message for transmitting one or more commands to the control unit;

extracting the specified location address and the flag from the TCW;

obtaining the message from the specified location address based on the flag having a first value indicating direct addressing, the message comprising one or more I/O commands;

gathering one or more I/O commands from command locations specified by a list of addresses identified by the specified location address to form the message based on the flag having a second value indicating indirect addressing, the message comprising the gathered one or more I/O commands; and

forwarding the message to the control unit for execution.

10. The apparatus of claim 9 wherein the list of addresses comprises two or more I/O commands, and the forwarded message comprises the two or more I/O commands.

11. The apparatus of claim 9 wherein the one or more I/O commands are included in a transport command control block (TCCB) and the location specified by the TCW is the location of the TCCB.

12. The apparatus of claim 11 wherein the TCCB further includes a header and a variable length transport control area, the header comprising information about the variable length transport control area, the variable length transport control area comprising one or more I/O commands, the header configured to specify a format of the one or more I/O commands.

13. The apparatus of claim 11 wherein the TCCB further includes a trailer for providing a check word and specifying the amount of data to transfer.

14. The apparatus of claim 9 wherein at least one of the one or more I/O commands and the gathered one or more I/O commands includes command codes and control data.

15. 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 address and a flag, the flag indicating whether the TCW directly or indirectly addresses a message for transmitting one or more commands to the control unit;

extracting the specified location address and the flag from the TCW;

obtaining the message from the specified location address based on the flag having a first value indicating direct addressing, the message comprising one or more I/O commands;

gathering one or more I/O commands from command locations specified by a list of addresses identified by the specified location address to form the message based on the flag having a second value indicating indirect addressing, the message comprising the gathered one or more I/O commands; and

forwarding the message to the control unit for execution.

16. The method of claim 15 wherein the one or more I/O commands are included in a transport command control block (TCCB) and the location specified by the TCW is the location of the TCCB.

17. The method of claim 16 wherein the TCCB further includes a trailer to provide a check word and specifying the amount of data to transfer.

18. The method of claim 15 wherein at least one of the one or more I/O commands and the gathered one or more I/O commands includes command codes and control data.

19. The method of claim 15 wherein the host computer includes a channel subsystem and the method is performed by the channel subsystem.

20. The method of claim 15 wherein the TCW is obtained from a host operating system.