18.1 PCI Root Bridge I/O Protocol Drivers
UEFI firmware for a platform typically implements a Root Bridge Driver that
produces the PCI Root Bridge I/O Protocol. This code is chipset specific and
directly accesses the chipset resources producing the services of the PCI Root
Bridge I/O Protocol. A sample driver for systems with a PC-AT-compatible
chipset is included in EDK II. The source code for this driver is found in the
EDK II package called PcAtChipsetPkg
in the directory
PcAtChipsetPkg/PciHostBridgeDxe
.