What I did

This PR resolves sonic-net/sonic-utilities#3925.

In this PR, I enhanced the show interfaces command to support specific BP port information display for multi-ASIC devices, for example, T2 Chassis. It means we can use commands like show interfaces status Ethernet-BP128 -d all to get the status of a backplane interface, e.g. Ethernet-BP128 itself, after this PR, just like what we used to do for a specific frontend interface (plus an extra -d all of course).

The commands I updated for getting specific BP interface information:

• show interfaces description
• show interfaces status
• show interfaces tpid
• show interfaces counters
• show interfaces autoneg status
• show interfaces link-training status
• show interfaces fec status

Please note that nothing has changed when running these commands on a single-ASIC device, and nothing has changed when running these commands on a multi-ASIC device without specifying an interface. The only behavior change is when we run the above commands for a specific interface on a multi-ASIC device.

How I did it

How to verify it

We can try the following commands after this PR to see the information of the backplane interface Ethernet-BP128 itself:

• show interfaces description Ethernet-BP128 -d all
• show interfaces status Ethernet-BP128 -d all
• show interfaces tpid Ethernet-BP128 -d all
• show interfaces counters -i Ethernet-BP128 -d all
• show interfaces autoneg status Ethernet-BP128 -d all
• show interfaces link-training status Ethernet-BP128 -d all
• show interfaces fec status Ethernet-BP128 -d all

Previous command output (if the output of a command-line utility has changed)

Before this PR, when we run show interfaces status Ethernet-BP128 -d all, the output will be empty:

admin@dut:~$ show int status Ethernet-BP128 -d all
     Interface                Lanes    Speed    MTU    FEC         Alias           Vlan    Oper    Admin    Type    Asym PFC
--------------  -------------------  -------  -----  -----  ------------  -------------  ------  -------  ------  ----------

New command output (if the output of a command-line utility has changed)

After this PR, when we run show interfaces status Ethernet-BP128 -d all, the output will be something like the following:

admin@dut:~$ show int status Ethernet-BP128 -d all
     Interface                Lanes    Speed    MTU    FEC         Alias           Vlan    Oper    Admin    Type    Asym PFC
--------------  -------------------  -------  -----  -----  ------------  -------------  ------  -------  ------  ----------
Ethernet-BP128  1700,1701,1702,1703     100G   9000    N/A  Eth310-ASIC1  PortChannel38      up       up     N/A         off