Mon, Nov 30, 2020 at 06:01:43PM CET, edwin.peer@broadcom.com wrote:

On Mon, Nov 23, 2020 at 1:40 AM Jiri Pirko [off-list ref] wrote:

quoted

quoted

Why can't this be implied by port break-out configuration? For higher
speed signalling modes like PAM4, what's the difference between a
port with unused lanes vs the same port split into multiple logical
ports? In essence, the driver could then always choose the slowest

There is a crucial difference. Split port is configured alwasy by user.
Each split port has a devlink instace, netdevice associated with it.
It is one level above the lanes.

Right, but the one still implies the other. Splitting the port implies fewer
lanes available.

I understand the concern if the device cannot provide sufficient MAC
resources to provide for the additional ports, but leaving a net device
unused (with the option to utilize an additional, now spare, port) still
seems better to me than leaving lanes unused and always wasted.

I don't follow what exactly are you implying. Could you elaborate a bit
more?

Otherwise, the earlier suggestion of fully specifying the forced link
mode (although I don't think Andrew articulated it quite that way)
instead of a forced speed and separate lane mode makes most
sense.

Regards,
Edwin Peer