PCIe lanes confusion

[engr.waqas]

Considering the following scenario:

A designer wants to connect 3 devices on a PCIe x4 finger edge connector, commonly found on mother boards. All 3 devices will be populated on the same PCIe card. One device has 1 port of 2 lanes i.e (1 x2 PCIe port) Remaining two devices have 1 port of 1 lane (1 x1 PCIe port) each.

Scheme 1:


Scheme 2:



I've seen scheme 1 in the datasheets of some PCIe switches. I want to know if a PCIe switch is really required in this case.

What if we omit the switch and just split the PCIe lanes?

Will it be a legit PCIe network?

If yes then how will bus numbers be assigned?

Kindly ask if there is a need for clarification.

 

[FvM]

PCIe spec says:

Optional Link negotiation behaviors include Lane reversal, variable width Links, splitting of Ports
into multiple Links and the configuration of a crosslink.

So the question is if the peer (e.g. the motherboard's PCIe bridge) supports it. I guess, it won't.