Determining extended capability of a channel path

• US 8,838,860 B2
• Filed: 03/15/2013
• Issued: 09/16/2014
• Est. Priority Date: 02/14/2008
• Status: Active Grant

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Gainey, Charles W. Jr., Casper, Daniel F.
• Primary Examiner(s): Abad, Farley
• Assistant Examiner(s): YU, HENRY W
• Application Number:
  US13/833,378
• Publication Number:
  US 20130205050A1
• Time in Patent Office: 550 Days
• Field of Search: 710/5, 710/11, 710/14, 710/20, 710/28, 710/62, 710/72, 710/74, 710/107, 710/113, 711/4, 711/112, 711/154, 370/389, 370/412, 370/476, 370/311, 370/338, 370/392
• US Class Current: 710/74
• CPC Class Codes: G06F 13/12 using hardware independent of the central processor, e.g. channel or peripheral processor
• CPC Class Codes: G06F 13/4022 using switching circuits, e.g. switching matrix, connection or expansion network G06F13/4009 takes precedence
• CPC Class Codes: G06F 13/4282 on a serial bus, e.g. I2C bus, SPI bus on daisy chain buses G06F13/4247
• CPC Class Codes: G06F 2213/4004 Universal serial bus hub with a plurality of upstream ports
• CPC Class Codes: G06F 3/00 Input arrangements for transferring data to be processed into a form capable of being handled by the computer; Output arrangements for transferring data from processing unit to output unit, e.g. interface arrangements
• CPC Class Codes: G06F 3/002 Specific input/output arrangements not covered by G06F3/01 - G06F3/16 other optical apparatus G02B27/00
• CPC Class Codes: G06F 3/0635 by changing the path, e.g. traffic rerouting, path reconfiguration

Abstract

A computer program product includes a tangible storage storing instructions for performing a method. The method includes receiving a request at a channel subsystem in a host computer system from an operating system in the host computer system to provide a channel path description for a channel path, the channel subsystem configured to direct information flow between memory and the control unit via the channel path; and outputting from the channel subsystem to the operating system, a channel path description block including the channel path description for the channel path in response to the request. The channel path description block includes: a descriptor field (DESC) indicating that the channel path supports a Fiber Channel protocol for commanding an I/O operation; and an extension support indicator field (F) specifying whether the channel path supports an extension to the Fiber Channel protocol.

Claims

1. A computer program product for determining extended capability of a channel path in an input/output (I/O) processing system, the computer program product comprising:

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

receiving a request at a channel subsystem in a host computer system from an operating system in the host computer system to provide a channel path description for a channel path, wherein the channel path includes a channel configured to be coupled to a control unit configured to operate and control one or more I/O devices, the channel subsystem configured to direct information flow between memory and the control unit via the channel path; and

outputting from the channel subsystem to the operating system, a channel path description block including the channel path description for the channel path in response to the request, wherein the channel path description block includes;

a descriptor field (DESC) indicating that the channel path supports a Fibre Channel protocol for commanding an I/0 operation; and

an extension support indicator field (F) specifying whether the channel path supports an extension to the Fibre Channel protocol.

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

the extension support indicator field (F) is contained within a channel description specific data (CDSD) field.

3. The computer program product of claim 2, wherein in response to the F field being ‘

1’

, the CDSD includes a maximum data count field indicating a maximum count of a sum of data count fields in all device control words (DCWs) in a transport command area (TCA) of a command message supported by the channel path when communicating via the extension to the Fibre Channel protocol.

4. The computer program product of claim 1, wherein the Fibre Channel protocol supports channel command word (CCW) channel programs configured to support at least one CCW that specifies a command for performing an I/O operation, and the extension to the Fibre Channel protocol supports transport control word (TCW) channel programs configured to support at least one transport command control block (TCCB), the TCCB configured to be sent from the channel subsystem to the control unit and configured to hold a plurality of commands for performing an I/O operation.

5. The computer program product of claim 1, wherein the descriptor field indicates that the channel path supports the Fibre Channel protocol, and the extension support indicator field is included in a channel description specific data (CDSD) field that is defined as a function of the descriptor field.

6. The computer program product of claim 3, wherein in response to the F field being ‘

0’

, the maximum data count field has a value of ‘

0’

.

7. The computer program product of claim 3, wherein the method further comprises:

in response to the descriptor field (DESC) not indicating that the channel path is capable of performing both a command mode link protocol supporting the Fibre Channel protocol and an extension to the Fibre Channel protocol using transport mode, the channel description specific data (CDSD) field absent the extension support indicator field (F) specifying whether the channel path supports an extension to the Fibre Channel protocol.

8. The computer program product of claim 3, wherein the TCA is included in a transport command control block (TCCB) sent from a channel to a control unit, the TCA comprising one or more DCWs, and wherein the maximum data count field represents a number of 64K bytes of data.

9. An apparatus for determining extended capability of a channel path in an input/output (I/O) processing system, the apparatus comprising:

a channel subsystem in a host computer system for communication with a control unit via a channel path, the channel subsystem including one or more channel paths including one or more channels configured to be coupled to a control unit configured to operate and control one or more I/O devices, the channel subsystem configured to direct information flow between memory and one or more I/O devices via the channel path, the channel subsystem configured to perform a method comprising;

receiving a request at the channel subsystem from an operating system in the host computer system to provide a channel path description for the channel path; and

outputting from the channel subsystem to the operating system, a channel path description block including the channel path description for the channel path in response to the request, wherein the channel path description block includes;

a descriptor field (DESC) indicating that the channel path supports a Fibre Channel protocol for commanding an I/O operation; and

an extension support indicator field (F) specifying whether the channel path supports an extension to the Fibre Channel protocol.

10. The apparatus of claim 9, wherein:

the extension support indicator field (F) is contained within a channel description specific data (CDSD) field.

11. The apparatus of claim 10, wherein in response to the extension support indicator field (F) being ‘

1’

, the CDSD includes a maximum data count field indicating a maximum count of a sum of data count fields in all device control words (DCWs) in a transport command area (TCA) of a command message supported by the channel path when communicating via the extension to the Fibre Channel protocol.

12. The apparatus of claim 9, wherein the Fibre Channel protocol supports channel command word (CCW) channel programs configured to support at least one CCW that specifies a command for performing an I/O operation, and the extension to the Fibre Channel protocol supports transport control word (TCW) channel programs configured to support at least one transport command control block (TCCB), the TCCB configured to be sent from the channel subsystem to the control unit and configured to hold a plurality of commands for performing an I/O operation.

13. The apparatus of claim 9, wherein the descriptor field indicates that the channel path supports the Fibre Channel protocol, and the extension support indicator field is included in a channel description specific data (CDSD) field that is defined as a function of the descriptor field.

14. The apparatus of claim 10, wherein in response to the F field being ‘

0’

, the maximum data count field has a value of ‘

0’

.

15. The apparatus of claim 10, wherein the method further comprises:

in response to the descriptor field (DESC) not indicating that the channel path is capable of performing both a command mode link protocol supporting the Fibre Channel protocol and an extension to the Fibre Channel protocol using transport mode, the channel description specific data (CDSD) field absent the extension support indicator field (F) specifying whether the channel path supports an extension to the Fibre Channel protocol.

16. The apparatus of claim 10, wherein the TCA is included in a transport command control block (TCCB) sent from a channel to a control unit, the TCA comprising one or more DCWs, and wherein the maximum data count field represents a number of 64K bytes of data.

17. A method for determining extended capability of a channel path in an input/output (I/O) processing system, the method comprising:

receiving a request at a channel subsystem in a host computer system from an operating system in the host computer system to provide a channel path description for a channel path, wherein the channel path includes a channel configured to be coupled to a control unit configured to operate and control one or more I/O devices, the channel subsystem configured to direct information flow between memory and the control unit via the channel path; and

outputting from the channel subsystem to the operating system a channel path description block including the channel path description for the channel path in response to the request, wherein the channel path description block includes;

a descriptor field indicating that the channel path supports a Fibre Channel protocol for commanding an I/O operation; and

an extension support indicator field specifying whether the channel path supports an extension to the Fibre Channel protocol.

18. The method of claim 17, wherein:

the F Field is contained within a channel description specific data (CDSD) field.

19. The method of claim 18 wherein in response to the extension support indicator field (F) being ‘

1’

, the CDSD includes a maximum data count field indicating a maximum count of a sum of data count fields in all device control words (DCWs) in a transport command area (TCA) of a command message supported by the channel path when communicating via the extension to the Fibre Channel protocol.

20. The method of claim 17 wherein the Fibre Channel protocol supports channel command word (CCW) channel programs configured to support at least one CCW that specifies a command for performing an I/O operation, and the extension to the Fibre Channel protocol supports transport control word (TCW) channel programs configured to support at least one transport command control block (TCCB), the TCCB configured to be sent from the channel subsystem to the control unit and configured to hold a plurality of commands for performing an I/O operation.

21. The method of claim 17, wherein the descriptor field indicates that the channel path supports the Fibre Channel protocol, and the extension support indicator field is included in a channel description specific data (CDSD) field that is defined as a function of the descriptor field.

22. The method of claim 18, wherein in response to the F field being ‘

0’

, the maximum data count field has a value of ‘

0’

.

23. The method of claim 18, further comprising:

in response to the descriptor field (DESC) not indicating that the channel path is capable of performing both a command mode link protocol supporting the Fibre Channel protocol and an extension to the Fibre Channel protocol using transport mode, the channel description specific data (CDSD) field absent the extension support indicator field (F) specifying whether the channel path supports an extension to the Fibre Channel protocol.

24. The method of claim 18, wherein the TCA is included in a transport command control block (TCCB) sent from a channel to a control unit, the TCA comprising one or more DCWs, and wherein the maximum data count field represents a number of 64K bytes of data.