Indirect addressing of channels via logical channel groups

• US 5,568,648 A
• Filed: 06/06/1995
• Issued: 10/22/1996
• Est. Priority Date: 06/05/1991
• Status: Expired due to Term

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Coscarella, Anthony, Temple, Joseph, Sachs, Martin W.
• Primary Examiner(s): Harrell, Robert B.
• Application Number:
  US08/471,475
• Time in Patent Office: 504 Days
• Field of Search: 364/DIG. 1 MS, 364/DIG. 2 MS, 364/, 395/842, 395/858, 395/821, 395/823, 395/416, 395/474, 395/200.2, 395/830, 395/846, 395/862, 395/869, 370/58.2, 370/60, 370/81
• US Class Current: 710/42
• CPC Class Codes: G06F 13/122 where hardware performs an I/O function other than control of data transfer

Abstract

A computer system for using logical channel groups to indirectly address channels. The computer system includes a processor, a memory, and an input/output (IO) system for transferring information between devices and the processor. The IO system includes channels, channel path identifiers for identifying the channels, logical channel groups having lists of the channel path identifiers, and subchannels having pointers to the logical channel groups. The IO system also includes one or more switches for routing information between the channels and devices.

Claims

1. In a computer system comprising a plurality of channels, an active data unit, and one or more peripheral devices, an IO subsystem for establishing physical paths between the active data unit and the peripheral devices using the channels, the subsystem comprising:

a plurality of channel path identifiers for identifying the channels;

a computer memory having a finite storage capacity;

a plurality of logical channel groups comprising lists that store channel path identifiers, said lists stored in said computer memory, said lists storing varying numbers of channel path identifiers, said lists having a storage capacity that is limited only by said finite storage capacity of said computer memory; and

a plurality of subchannels each exclusively assigned to one of said peripheral devices, each of said subchannels maintaining one or more pointers, each of said pointers addressing one of said logical channel groups.

2. The subsystem of claim 1, wherein ranges of said channel path identifiers are represented by first channel path identifiers and last channel path identifiers.

3. The subsystem of claim 2, wherein each of said logical channel groups comprises:

one of said first channel path identifiers;

one of said last channel path identifiers; and

flag means for identifying optimized channels, wherein said optimized channels represent channels which are each optimized to perform a particular function.

4. The subsystem of claim 3, further comprising:

busy means for identifying busy channels;

first mask means, coupled to said flag means, for identifying said optimized channels;

second mask means for generating a channel vector according to one of said ranges represented by said first channel path identifier and said last channel path identifier;

AND means, coupled to said busy means, first mask means, and second mask means, for generating a result vector;

CTLZ means, coupled to said AND means, for analyzing said result vector to determine whether an available channel exists; and

means for using said available channel to establish one of said physical paths if said available channel exists.

5. The subsystem of claim 4, wherein said AND means comprises means for specifying idle channels within said range by AND'"'"'ing said busy vector and channel vector.

6. The subsystem of claim 5, wherein said available channel comprises one of said idle channels within said range.

7. The subsystem of claim 4, wherein said AND means comprises means for specifying idle and optimized channels within said range by AND'"'"'ing said busy vector, mask vector, and channel vector.

8. The subsystem of claim 7, wherein said available channel comprises one of said idle and optimized channels within said range.

9. The subsystem of claim 4, wherein said CTLZ means comprises:

means for scanning said result vector in a first direction if a START CHANNEL operation is being performed; and

means for scanning said result vector in a second direction if a RECONNECT CHANNEL operation is being performed.

10. The subsystem of claim 1, wherein each pointer maintained by each subchannel addresses a logical channel group storing channel path identifiers that identify channels that are connected to a peripheral device assigned to said each subchannel.

11. The subsystem of claim 1 in which the system includes switches connected to said peripheral devices and said channels, wherein the channel path identifiers in any one of said logical channel groups identify channels which are electrically coupled to a particular one of said peripheral devices via a particular one of said switches.

12. In a computer system having an active data unit, a plurality of channels, and a plurality of peripheral devices, a method for establishing a communication link between the active data unit and one of the peripheral devices, the method comprising the steps of:

(1) establishing a logical channel between the active data unit and the peripheral device;

(2) associating one or more of said channels with said logical channel; and

(3) establishing a physical path via one of said associated channels between the active data unit and the peripheral device;

wherein step (1) comprises the steps of;

(a) identifying a subchannel associated with the peripheral device, wherein said subchannel includes pointers that address logical channel groups, said logical channel groups comprising lists that store channel path identifiers that identify channels, said lists stored in a computer memory, said lists storing varying numbers of channel path identifiers, said lists having a storage capacity that is limited only by a storage capacity of the computer memory; and

(b) selecting one of said logical channel groups.

13. The method of claim 12, wherein step (2) comprises the step of:

selecting one of the channel path identifiers stored in said selected logical channel group.

14. The method of claim 13, wherein step (3) comprises the step of:

establishing a physical path between the active data unit and the peripheral device using a channel identified by said selected channel path identifier.

15. The method of claim 12, wherein each pointer maintained by said subchannel addresses a logical channel group storing channel path identifiers that identify channels that are connected to the peripheral device assigned to the subchannel.

16. The method of claim 12 in which the system includes switches connected to the peripheral devices and the channels, wherein the channel path identifiers in each of the logical channel groups identify channels which are electrically coupled to the peripheral device via a particular one of the switches.

17. A computer system, comprising:

an active data unit;

a plurality of peripheral devices; and

an IO subsystem to transfer information between said peripheral devices and said active data unit, said IO subsystem comprising;

multiple channels electrically coupled to said active data unit;

one or more switches each electrically coupled to one or more of said channels and one or more of said peripheral devices, for routing information between said channels and said peripheral devices;

a plurality of channel path identifiers each identifying one of said channels;

a computer memory having a finite storage capacity;

a plurality of logical channel groups comprising lists that store channel path identifiers, said lists stored in said computer memory, said lists storing varying numbers of channel path identifiers, said lists having a storage capacity that is limited only by said finite storage capacity of said computer memory, channel path identifiers in any one of said logical channel groups identifying channels which are electrically coupled to a particular one of said peripheral devices via a particular one of said switches;

a plurality of subchannels each exclusively assigned to one of said peripheral devices, each of said subchannels maintaining one or more pointers each addressing one of said logical channel groups; and

means for establishing a physical communication path between said active data unit and one of said peripheral devices by selecting a channel path identifier in a logical channel group addressed by a pointer maintained by a subchannel assigned to said peripheral device, wherein said physical communication path includes a channel identified by said selected channel path identifier.

18. The system of claim 17, wherein each pointer maintained by each subchannel addresses a logical channel group storing channel path identifiers that identify channels that are connected to a peripheral device assigned to said each subchannel.