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

• US 9,292,224 B2
• Filed: 06/13/2014
• Issued: 03/22/2016
• 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., Flanagan, John R., Huang, Catherine C., Kalos, Matthew J., Njoku, Ugochukwu C., Riedy, Dale F., Sittmann, Gustav E. III
• Primary Examiner(s): Tsai, Henry
• Assistant Examiner(s): Hassan, Aurangzeb
• Application Number:
  US14/304,383
• Publication Number:
  US 20140297891A1
• Time in Patent Office: 648 Days
• Field of Search: None
• US Class Current: 1/1
• 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 is provided for performing a method including: sending a transport command word (TCW) to an I/O subsystem, the TCW specifying a location address and indicating whether the TCW directly or indirectly addresses a message; extracting the location address from the TCW; obtaining the message from the specified location address based on the TCW indicating direct addressing, the message including the one or more I/O commands; gathering the 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 TCW indicating indirect addressing; and generating a message including the one or more I/O commands.

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 non-transitory tangible storage medium readable by a processing circuit and storing instructions for execution by the processing circuit for performing a method comprising;

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

receiving the TCW at the I/O subsystem;

extracting the specified location address from the TCW;

obtaining the message from the specified location address based on the TCW indicating direct addressing, the message including the one or more I/O commands;

gathering the 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 TCW indicating indirect addressing; and

generating a message including the one or more I/O commands.

2. The computer program product of claim 1, wherein the method further comprises forwarding the message to the control unit for execution.

3. The computer program product of claim 1, wherein the TCW includes a flag, the flag having a value that indicates whether the TCW directly or indirectly addresses the message, and extracting includes extracting the flag from the TCW.

4. The computer program product of claim 3, wherein the message is obtained based on the flag having a first value indicating direct addressing, and the one or more I/O commands are gathered from the command locations based on the flag having a second value indicating indirect addressing.

5. The computer program product of claim 1, wherein the message is configured to hold a plurality of commands.

6. The computer program product of claim 1, wherein the message is a transport command control block (TCCB) configured to hold a plurality of I/O commands, and the location specified by the TCW is the location of the TCCB.

7. The computer program product of claim 6, 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.

8. The computer program product of claim 6, wherein the TCCB further includes a trailer for providing a check word and specifying the amount of data to transfer.

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. 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:

sending a transport command word (TCW) for an I/O operation to an I/O subsystem via an application executed in the host computer system, the TCW specifying a location address and indicating whether the TCW directly or indirectly addresses a message for transmitting one or more commands to the control unit;

receiving the TCW by the I/O subsystem;

extracting the specified location address from the TCW;

obtaining the message from the specified location address based on the TCW indicating direct addressing, the message including the one or more I/O commands;

gathering the 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 TCW indicating indirect addressing; and

generating a message including the one or more I/O commands.

11. The apparatus of claim 10, wherein the TCW includes a flag, the flag having a value that indicates whether the TCW directly or indirectly addresses the message, and extracting includes extracting the flag from the TCW.

12. The apparatus of claim 11, wherein the message is obtained based on the flag having a first value indicating direct addressing, and the one or more I/O commands are gathered from the command locations based on the flag having a second value indicating indirect addressing.

13. The apparatus of claim 10, wherein the message is configured to hold a plurality of commands.

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

15. The apparatus of claim 10, wherein the message is a transport command control block (TCCB) configured to hold a plurality of I/O commands, and the location specified by the TCW is the location of the TCCB.

16. The apparatus of claim 10, 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.

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

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

receiving the TCW at the I/O subsystem;

extracting the specified location address from the TCW;

obtaining the message from the specified location address based on the TCW indicating direct addressing, the message including the one or more I/O commands;

gathering the 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 TCW indicating indirect addressing; and

generating a message including the one or more I/O commands.

18. The method of claim 17, further comprising forwarding the message to the control unit for execution.

19. The method of claim 17, wherein the TCW includes a flag, the flag having a value that indicates whether the TCW directly or indirectly addresses the message, and extracting includes extracting the flag from the TCW.

20. The method of claim 17, wherein the message is a transport command control block (TCCB) configured to hold a plurality of I/O commands, and the location specified by the TCW is the location of the TCCB.