On Mon, 12 Oct 2020 15:33:45 +0000 Danielle Ratson wrote:

quoted

What's the use for this in practical terms? Isn't the lane count basically
implied by the module that gets plugged in?  

The use is to enable the user to decide how to achieve a certain speed. 
For example, if he wants to get 100G and the port has 4 lanes, the
speed can be achieved it using both 2 lanes of 50G and 4 lanes of
25G, as a port with 4 lanes width can work in 2 lanes mode with
double speed each. So, by specifying "lanes 2" he will achieve 100G
using 2 lanes of 50G.

Can you give a concrete example of serdes capabilities of the port,
what SFP gets plugged in and what configuration user wants to select?