[platform api] Fix sfp index

[antoninamelnyk]

Signed-off-by: Antonina Melnyk antoninax.melnyk@intel.com

Description of PR

Summary:
Fixes # (issue)
Change sfp index from 0-based to 1-based

Type of change

• Bug fix
• Testbed and Framework(new/improvement)
• Test case(new/improvement)

Approach

What is the motivation for this PR?

On practice chassis.get_sfp function accept a 1-based index as its argument. Before the fix, returned values were shifted by one.

How did you do it?

Change sfp index from 0-based to 1-based

How did you verify/test it?

Test is locally

Any platform specific information?

Supported testbed topology if it's a new test case?

Documentation

[jleveque]

On practice chassis.get_sfp function accept a 1-based index as its argument. Before the fix, returned values were shifted by one.

This is not true. chassis.get_sfp() accepts a 0-based index. Please see here

    def get_sfp(self, index):
        """
        Retrieves sfp represented by (0-based) index <index>
        Args:
            index: An integer, the index (0-based) of the sfp to retrieve.
                   The index should be the sequence of a physical port in a chassis,
                   starting from 0.
                   For example, 0 for Ethernet0, 1 for Ethernet4 and so on.
        Returns:
            An object dervied from SfpBase representing the specified sfp
        """

[antoninamelnyk]

chassis.get_sfp() accepts a 0-based index.

Ok, I see. But most implementations have this method overridden to accept 1-based index. So returned values in tests are shifted by one. Do we need platform-specific exceptions for this?

[jleveque]

chassis.get_sfp() accepts a 0-based index.

Ok, I see. But most implementations have this method overridden to accept 1-based index. So returned values in tests are shifted by one. Do we need platform-specific exceptions for this?

Can you please link to an example of an implementation where the method is overridden to accept 1-based index?

[antoninamelnyk]

Can you please link to an example of an implementation where the method is overridden to accept 1-based index?

For example, Arista implementation or Mellanox implementation

[jleveque]

Can you please link to an example of an implementation where the method is overridden to accept 1-based index?

For example, Arista implementation or Mellanox implementation

This is due to the fact that these vendors have defined their starting index to be 1 rather than 0 (example). If you look through all the platforms, you will see many which index their ports starting from 0. We suggest vendors index their ports starting from 0 (example). If you read the SONiC Porting Guide, "if the front panel ports are starting from 1, the index should start from 1. If the front panel ports start from 0, the index should start form 0. The break out ports from the same physical port should have same index.". Therefore, the base of this index is platform-specific.

[yxieca]

Should not merge this change.