preventing pci slots from beeing used / having the cards in these slots ignored

Issue

• We have installed a system at a customer's site with InfiniBand cards from two different vendors: Intel and Mellanox.
  At present, the driver is not capable of handling both cards, but one is in the works which will do so. Until then, they are looking for a means to tell the kernel to ignore one of the cards. Blacklisting the entire driver is not possible, because it is required to drive the other card. The only means I have found so far is the "pci=lastbus=N" kernel
  parameter, and maybe I can convince them to put the card into a PCI slot at the far end of the range, but if this is impossible: what other ways are there?
• preventing pci slots from beeing used / having the cards in these slots ignored