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

• US 8,117,347 B2
• Filed: 02/14/2008
• Issued: 02/14/2012
• 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): Hafiz, Tariq
• Assistant Examiner(s): Hassan, Aurangzeb
• Application Number:
  US12/031,201
• Publication Number:
  US 20090210563A1
• Time in Patent Office: 1,461 Days
• Field of Search: 710/5
• 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;

obtaining a transport command word (TCW) for an I/O operation, the TCW comprising a flag field comprising a flag, and a transport command control block (TCCB) address field comprising a TCCB address, the flag indicating whether the TCCB address field directly or indirectly addresses a TCCB;

obtaining a TCCB from a location identified by the TCCB address responsive to the flag having a first value indicating direct addressing, the TCCB comprising 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;

gathering the TCCB from one or more locations specified by a list of addresses identified by the TCCB address responsive to the flag having a second value indicating indirect addressing, the TCCB comprising 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; and

forwarding the TCCB to the control unit for execution.

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

4. The computer program product of claim 1 wherein the header is configured to specify a format of at least one of the one or more I/O commands.

5. The computer program product of claim 1 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 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. The computer program product of claim 1, wherein:

the TCW is configured to hold an output-data address field, an input-data address field, a transport-status-block address field, the TCCB address field, an output count field, and an input count field; and

the output-data address field comprises an output data address.

10. The computer program product of claim 1, wherein:

the TCW is configured to hold an output-data address field, an input-data address field, a transport-status-block address field, the TCCB address field, an output count field, and an input count field; and

the input-data address field comprises an input data address.

11. The computer program product of claim 1, wherein the flag field further comprises a second flag and a third flag, the second flag indicating whether an input data address is a direct address or an indirect address, the third flag indicating whether an output data address is a direct address or an indirect address.

12. An apparatus 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 host computer system configured to perform a method comprising:

obtaining a transport command word (TCW) for an I/O operation, the TCW comprising a flag field comprising a flag, and a transport command control block (TCCB) address field comprising a TCCB address, the flag indicating whether the TCCB address field directly or indirectly addresses the TCCB;

obtaining a TCCB from a location identified by the TCCB address responsive to the flag having a first value indicating direct addressing, the TCCB comprising 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;

gathering the TCCB from one or more locations specified by a list of addresses identified by the TCCB address responsive to the flag having a second value indicating indirect addressing, the TCCB comprising 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; and

forwarding the TCCB to the control unit for execution.

13. The apparatus of claim 12 wherein the list of addresses comprises a location of two or more I/O commands, and the TCCB of the forwarded message comprises the two or more I/O commands.

14. The apparatus of claim 12 wherein the one or more I/O commands are included in the TCCB.

15. The apparatus of claim 12 wherein the header is configured to specify a format of the one or more I/O commands.

16. The apparatus of claim 12 wherein the TCCB further includes a trailer for providing a check word and specifying the amount of data to transfer.

17. The apparatus of claim 12 wherein at least one of the one or more I/O commands includes command codes and control data.

18. The apparatus of claim 12, wherein

the TCW is configured to hold an output-data address field, an input-data address field, a transport-status-block address field, the TCCB address field, an output count field, and an input count field;

and

the output-data address field comprises an output data address.

19. The apparatus of claim 12, wherein:

the TCW is configured to hold an output-data address field, an input-data address field, a transport-status-block address field, the TCCB address field, an output count field, and an input count field; and

the input-data address field comprises an input data address.

20. The apparatus of claim 12, wherein the flag field further comprises a second flag and a third flag, the second flag indicating whether an input data address is a direct address or an indirect address, the third flag indicating whether an output data address is a direct address or an indirect address.

21. A 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 method comprising:

obtaining a transport command word (TCW) for an I/O operation, the TCW comprising a flag field comprising a flag, and a transport command control block (TCCB) address field comprising a TCCB address, the flag indicating whether the TCCB address field directly or indirectly addresses the TCCB;

obtaining a TCCB from a location specified by the TCCB address responsive to the flag having a first value indicating direct addressing, the TCCB comprising 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;

gathering the TCCB from one or more locations specified by a list of addresses identified by the TCCB address responsive to the flag having a second value indicating indirect addressing, the TCCB comprising 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; and

forwarding the TCCB to the control unit for execution.

22. The method of claim 21 wherein the one or more I/O commands are included in the TCCB.

23. The method of claim 22 wherein the TCCB further includes a trailer to provide a check word and specifying the amount of data to transfer.

24. The method of claim 21 wherein at least one of the one or more I/O commands includes command codes and control data.

25. The method of claim 21 wherein the host computer includes a channel subsystem and the method is performed by the channel subsystem.

26. The method of claim 21 wherein the TCW is obtained from a host operating system.

27. The method of claim 21, wherein:

the TCW is configured to hold an output-data address field, an input-data address field, a transport-status-block address field, the TCCB address field, an output count field, and an input count field; and

the input-data address field comprises an input data address.

28. The method of claim 21, wherein the flag field further comprises a second flag and a third flag, the second flag indicating whether an input data address is a direct address or an indirect address, the third flag indicating whether an output data address is a direct address or an indirect address.