We have 3 PCIe slots on a board, let's call them A, B and C. On this board, slot A will always be populated with a PCIe device, however, among slots B and C, only one of them will be populated.
There is only one PCIe link on slot A. So, in order to communicate via PCIe with either slot B or slot C, the same PCIe TXP/RXP/TXN/RXN signal on slot A should be routed to both slot B and slot C.
I don't know if this would be considered a common scenario. Probably not. I haven't been able to find out any layout guidelines covering this particular case.
Any ideas would be appreciated.