EXCEPTION CONDITION HANDLING AT A CHANNEL SUBSYSTEM IN AN I/O PROCESSING SYSTEM

• US 20090210768A1
• 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., Ricci, Louis W., Carlson, Scott M., Hathorn, Roger G., Sittmann, Gustav E., Njoku, Ugochukwu C., Casper, Daniel F., Gainey, Charles W.
• Granted Patent: US 8,095,847 B2
• Time in Patent Office: Days
• US Class Current: 714/758
• CPC Class Codes: G06F 13/385 for adaptation of a particular data processing system to different peripheral devices

Abstract

A computer program product, apparatus, and method for handling exception condition feedback at a channel subsystem of an I/O processing system using data from a control unit are provided. 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 sending a command message to the control unit, and receiving a response message in response to the command message. The response message includes exception condition feedback identifying a termination reason code in response to unsuccessful execution of at least one command in the command message. The method also includes interrupting a CPU in the I/O processing system, and reporting status associated with the exception condition feedback to the CPU in an interrupt response block.

Claims

1. A computer program product for handling exception condition feedback at a channel subsystem of an input/output (I/O) processing system using data from 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;

sending a command message to the control unit;

receiving a response message in response to the command message, wherein the response message includes exception condition feedback identifying a termination reason code in response to unsuccessful execution of at least one command in the command message;

interrupting a central processing unit (CPU) in the I/O processing system; and

reporting status associated with the exception condition feedback to the CPU in an interrupt response block.

2. The computer program product of claim 1 wherein the termination reason code identifies one or more of:

invalidity of the command message, an invalid cyclic redundancy check (CRC), incorrect length of the command message, a transport command area header error, a device control word (DCW) specification error, a transfer direction specification error, a transport count specification error, and two active I/O operations to a common device address.

3. The computer program product of claim 1 wherein the exception condition feedback further includes a reason code qualifier providing encoded meaning corresponding to the termination reason code.

4. The computer program product of claim 3 wherein the reason code qualifier includes information on one or more of:

a length mismatch of the command message, a longitudinal redundancy check (LRC) error, and a field specification error in the command message.

5. The computer program product of claim 4 wherein the field specification error is one of:

a format field specification error, a reserved field specification error, a service action code field specification error, a flags field command chaining specification error, a control data count field specification error, a direction specification error, and a count specification error.

6. The computer program product of claim 1 wherein the response message includes a status section and an extended status section, the extended status section including the termination reason code.

7. The computer program product of claim 6 wherein the method further comprises:

copying information from a status flags field in the response message to the interrupt response block, wherein the status flags field indicates that the extended status section is included as part of the response message.

8. The computer program product of claim 6 wherein the status section includes one or more flags capable of declaring one of:

a device level exception, a link reject, a resetting event, a device requested program check, and a device requested program check with a possible interface control check.

9. The computer program product of claim 1 wherein the interrupt response block includes a sub-channel status and a sub-channel extended status, the sub-channel status identifying a check condition and the sub-channel extended status providing detail associated with the check condition.

10. The computer program product of claim 9 wherein the sub-channel extended status indicates at least one of:

a storage request limit exceeded, a count mismatch, an unsupported mode, an invalid transport control word, a device requested program check, a device requested program check with a possible interface control check, a storage exception, and an interface control check cause.

11. An apparatus for handling exception condition feedback in an input/output (I/O) processing system, the apparatus comprising:

a channel subsystem in communication with a control unit, the channel subsystem performing a method comprising;

sending a command message to the control unit;

receiving a response message in response to the command message, wherein the response message includes exception condition feedback identifying a termination reason code in response to unsuccessful execution of at least one command in the command message;

interrupting a central processing unit (CPU) in the I/O processing system; and

reporting status associated with the exception condition feedback to the CPU in an interrupt response block.

12. The apparatus of claim 11 wherein the termination reason code identifies one or more of:

invalidity of the command message, an invalid cyclic redundancy check (CRC), incorrect length of the command message, a transport command area header error, a device control word (DCW) specification error, a transfer direction specification error, a transport count specification error, and two active I/O operations to a common device address.

13. The apparatus of claim 11 wherein the exception condition feedback further includes a reason code qualifier providing encoded meaning corresponding to the termination reason code.

14. The apparatus of claim 13 wherein the reason code qualifier includes information on one or more of:

a length mismatch of the command message, a longitudinal redundancy check (LRC) error, and a field specification en-or in the command message.

15. The apparatus of claim 14 wherein the field specification error is one of:

a format field specification en-or, a reserved field specification error, a service action code field specification error, a flags field command chaining specification error, a control data count field specification error, a direction specification error, and a count specification error.

16. The apparatus of claim 11 wherein the response message includes a status section and an extended status section, the extended status section including the termination reason code.

17. The apparatus of claim 16 wherein the channel subsystem performing the method further comprises:

copying information from a status flags field in the response message to the interrupt response block, wherein the status flags field indicates that the extended status section is included as part of the response message.

18. The apparatus of claim 16 wherein the status section includes one or more flags capable of declaring one of:

a device level exception, a link reject, a resetting event, a device requested program check, and a device requested program check with a possible interface control check.

19. The apparatus of claim 11 wherein the interrupt response block includes a sub-channel status and a sub-channel extended status, the sub-channel status identifying a check condition and the sub-channel extended status providing detail associated with the check condition.

20. The apparatus of claim 19 wherein the sub-channel extended status indicates at least one of:

a storage request limit exceeded, a count mismatch, an unsupported mode, an invalid transport control word, a device requested program check, a device requested program check with a possible interface control check, a storage exception, and an interface control check cause.

21. A method for handling exception condition feedback at a channel subsystem of an input/output (I/O) processing system using data from a control unit, the method comprising:

sending a command message to the control unit;

receiving a response message in response to the command message, wherein the response message includes exception condition feedback identifying a termination reason code in response to unsuccessful execution of at least one command in the command message;

interrupting a central processing unit (CPU) in the I/O processing system; and

reporting status associated with the exception condition feedback to the CPU in an interrupt response block.

22. The method of claim 21 wherein the termination reason code identifies one or more of:

invalidity of the command message, an invalid cyclic redundancy check (CRC), incorrect length of the command message, a transport command area header error, a device control word (DCW) specification error, a transfer direction specification error, a transport count specification error, and two active I/O operations to a common device address, and further wherein the exception condition feedback further includes a reason code qualifier including information on one or more of;

a length mismatch of the command message, a longitudinal redundancy check (LRC) error, and a field specification error in the command message.

23. The method of claim 21 wherein the response message includes a status section and an extended status section, the extended status section including the termination reason code, and further wherein the status section includes one or more flags capable of declaring one of:

a device level exception, a link reject, a resetting event, a device requested program check, and a device requested program check with a possible interface control check.

24. The method of claim 23 further comprising:

copying information from a status flags field in the response message to the interrupt response block, wherein the status flags field indicates that the extended status section is included as part of the response message.

25. The method of claim 21 wherein the interrupt response block includes a sub-channel status and a sub-channel extended status, the sub-channel status identifying a check condition and the sub-channel extended status providing detail associated with the check condition indicating at least one of:

a storage request limit exceeded, a count mismatch, an unsupported mode, an invalid transport control word, a device requested program check, a device requested program check with a possible interface control check, a storage exception, and an interface control check cause.