Error message
xillybus: pci_request_regions() failed. Aborting.Meaning
This error message is issued when failing to take ownership of the memory region used to communicate directly with the processor's Xillybus peripheral.
This can happen when a removal of the Xillybus driver from the kernel failed partially, so that the driver couldn't release the resources. As a result, the memory region is considered still held by some driver.
Unless previous error messages imply that things have gone very wrong, this should never happen.
Recommended action
This error should be reported, if it appears on a just booted system.
To get Xillybus working again, reboot the host computer.