Hi, all When initializing a PCI device, during the pci_driver's probe function, pci_request_region is called. Inside the pci_request_region, it is just calling request_region with the values in pci_dev->resource[bar].start and end. But when is this pci->dev->resource values filled? Is it done by the BIOS(or UEFI) before linux boots? Probably not because this pci_dev struct is from linux and should be filled by linux code and I couldn't find where it's done. Chan Kim