PCI hotplug. We need to implement arbitration of bus number, BAR, and IO/memory forward windows.

[cl91]

[cl91]

We now report PCI bridge windows to the PnP manager and the IO resource arbitration process should assign valid BAR ranges that can fit into the bridge's forward windows to a hotplugged downstream device. What remains to be done is (1) Call IoInvalidateDeviceRelations when an interrupt is received for the bridge, indicating the presence of a hotplugged device, and (2) Call IoInvalidateDeviceState when the PCI bridge's forward windows are too small for the new device to fit (including the case that this bridge is unconfigured, ie. having a zero-sized forward window). This will trigger the whole sequence of resource rebalance, including potentially moving the bridge windows somewhere else (which will include stopping and starting all existing child devices under that bridge). (3) Reporting bus numbers to the PnP manager and request a new bus number if this PCI bridge is not assigned one by the firmware. This is rare though.