SAS Paired subtractive routing

• US 20100064060A1
• Filed: 04/02/2009
• Published: 03/11/2010
• Est. Priority Date: 09/05/2008
• Status: Active Grant

• Current Assignee: Avago Technologies General IP PTE Limited (Broadcom, Inc.)
• Original Assignee: LSI Corporation (Broadcom, Inc.)
• Inventors: Parry, Owen, Johnson, Stephen B., Petty, William K.
• Granted Patent: US 8,321,596 B2
• Time in Patent Office: Days
• US Class Current: 710/2
• 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

Abstract

An input port is assigned to a SAS expander device. An output port is assigned to the SAS expander device. The output port and the input port are defined to be paired with each other as a primary subtractive port. Only a SAS initiator address is programmed in the route table of the SAS expander. An OPEN command is sent out the output port upon receiving the OPEN command into the input port if the DEST of the OPEN command is not a direct attached device of the SAS expander device and the DEST is not in the route table of the SAS expander device. An OPEN command is sent out the input port upon receiving the OPEN command into the output port if the DEST of the OPEN command is not a direct attached device of the SAS expander device and the DEST is not in the route table of the SAS expander device.

Claims

1. A method for performing paired subtractive routing in a Serial Attached Small Computer System Interface (SAS) cascaded topology, comprising:

assigning an input port to a SAS expander device;

assigning an output port to the SAS expander device;

defining the output port and the input port to be paired with each other as a primary subtractive port;

programming only a SAS initiator address in the route table of the SAS expander;

sending an OPEN command out the output port upon receiving the OPEN command into the input port if the DEST of the OPEN command is not a direct attached device of the SAS expander device and the DEST is not in the route table of the SAS expander device; and

sending an OPEN command out the input port upon receiving the OPEN command into the output port if the DEST of the OPEN command is not a direct attached device of the SAS expander device and the DEST is not in the route table of the SAS expander device.

2. The method of claim 1, further including:

adding a second input port and a second output port to the SAS expander device;

defining the second input port and the second output port to be paired with each other as a secondary subtractive port; and

sending an OPEN command out the second output port upon receiving the OPEN command into the second input port if the DEST of the OPEN command is not a direct attached device of the SAS expander device and the DEST is not in the route table of the SAS expander device; and

sending an OPEN command out the second input port upon receiving the OPEN command into the second output port if the DEST of the OPEN command is not a direct attached device of the SAS expander device and the DEST is not in the route table of the SAS expander device.

3. The method of claim 2, wherein the secondary subtractive port operates for communication with the direct attached device of the SAS expander device.

4. The method of claim 1, wherein an OPEN command defaults to the primary subtractive port.

5. The method of claim 1, further including:

specifying the subtractive ports of the SAS expander via a modified routing attribute of a vendor unique SAS Management Protocol (SMP) function.

6. The method of claim 5, further including:

when a modified routing attribute exists for a port, the SAS initiator ignoring the SMP DISCOVER response attribute for the port and instead using the modified routing attribute for the port.

7. The method of claim 1, wherein the programming a SAS initiator address in the route table of the SAS expander further includes:

programming the route table for a self-configuration specified port, wherein the programming the route table for the port is performed by the SAS expander.

8. The method of claim 1, wherein the programming a SAS initiator address in the route table of the SAS expander further includes:

programming a SAS initiator address in the route table of the SAS expander using each SAS initiator in the SAS routing topology, each SAS initiator programming only the SAS initiator address for that SAS initiator in the route table of the SAS expander.

9. The method of claim 8, wherein the programming a SAS initiator address in the route table of the SAS expander is performed by each SAS initiator in the SAS routing topology, each SAS initiator programming only the SAS initiator address for that SAS initiator in the route table of the SAS expander further includes:

programming a SAS initiator address in the route table of the SAS expander using each SAS initiator in the SAS routing topology, each SAS initiator programming only the SAS initiator address for that SAS initiator in the route table of the SAS expander, and

wherein each SAS initiator only programs the SAS initiator address for that SAS initiator in the route table of one type of modified routing attribute port of the SAS expander, depending on the position of the SAS initiator in the SAS routing topology.

10. The method of claim 1, wherein a SAS initiator may be located at the top or the bottom of the SAS routing topology.

11. A system, comprising:

means for assigning an input port to a SAS expander device;

means for assigning an output port to the SAS expander device;

means for defining the output port and the input port to be paired with each other as a primary subtractive port;

means for programming only a SAS initiator address in the route table of the SAS expander;

means for sending an OPEN command out the output port upon receiving the OPEN command into the input port if the DEST of the OPEN command is not a direct attached device of the SAS expander device and the DEST is not in the route table of the SAS expander device; and

means for sending an OPEN command out the input port upon receiving the OPEN command into the output port if the DEST of the OPEN command is not a direct attached device of the SAS expander device and the DEST is not in the route table of the SAS expander device.

12. The system of claim 11, further including:

means for adding a second input port and a second output port to the SAS expander device;

means for defining the second input port and the second output port to be paired with each other as a secondary subtractive port; and

means for sending an OPEN command out the second output port upon receiving the OPEN command into the second input port if the DEST of the OPEN command is not a direct attached device of the SAS expander device and the DEST is not in the route table of the SAS expander device; and

means for sending an OPEN command out the second input port upon receiving the OPEN command into the second output port if the DEST of the OPEN command is not a direct attached device of the SAS expander device and the DEST is not in the route table of the SAS expander device.

13. The system of claim 12, wherein the secondary subtractive port operates for communication with the direct attached device of the SAS expander device.

14. The system of claim 11, wherein an OPEN command defaults to the primary subtractive port.

15. The system of claim 11, further including:

means for specifying the subtractive ports of the SAS expander via a modified routing attribute of a vendor unique SAS Management Protocol (SMP) function.

16. The system of claim 15, further including:

when a modified routing attribute exists for a port, the SAS initiator ignoring the SMP DISCOVER response attribute for the port and instead using the modified routing attribute for the port.

17. The system of claim 11, wherein the means for programming a SAS initiator address in the route table of the SAS expander further includes:

means for programming the route table for a self-configuration specified port, wherein the programming the route table for the port is performed by the SAS expander.

18. The system of claim 11, wherein the means for programming a SAS initiator address in the route table of the SAS expander further includes:

means for programming a SAS initiator address in the route table of the SAS expander using a SAS initiator in the SAS routing topology, and wherein each SAS initiator programs only the SAS initiator address for that SAS initiator in the route table of the SAS expander.

19. The system of claim 18, wherein the means for programming a SAS initiator address in the route table of the SAS expander is a SAS initiator in the SAS routing topology, and wherein each SAS initiator, programs only the SAS initiator address for that SAS initiator in the route table of the SAS expander further includes:

means for programming a SAS initiator address in the route table of the SAS expander using a SAS initiator in the SAS routing topology, and wherein each SAS initiator programs only the SAS initiator address for that SAS initiator in the route table of the SAS expander, and

wherein each SAS initiator only programs the SAS initiator address for that SAS initiator in the route table of one type of modified routing attribute port of the SAS expander, depending on the position of the SAS initiator in the SAS routing topology.

20. The system of claim 11, wherein a SAS initiator may be located at the top or the bottom of the SAS routing topology.

21. A computer-readable medium having computer-executable instructions for performing a method for performing paired subtractive routing in a Serial Attached Small Computer System Interface (SAS) cascaded topology, the method comprising:

assigning an input port to a SAS expander device;

assigning an output port to the SAS expander device;

defining the output port and the input port to be paired with each other as a primary subtractive port;

programming only a SAS initiator address in the route table of the SAS expander;

sending an OPEN command out the output port upon receiving the OPEN command into the input port if the DEST of the OPEN command is not a direct attached device of the SAS expander device and the DEST is not in the route table of the SAS expander device; and

sending an OPEN command out the input port upon receiving the OPEN command into the output port if the DEST of the OPEN command is not a direct attached device of the SAS expander device and the DEST is not in the route table of the SAS expander device.