Intel Extensible Firmware Interface - Manual (Page 491)

Protocols — PCI Bus Support
Version 1.10 12/01/02 12-73
EFI_PCI_IO_PROTOCOL.Pci.Read()
EFI_PCI_IO_PROTOCOL.Pci.Write()
Summary
Enable a PCI driver to access PCI controller registers in PCI configuration space.
Prototype
typedef
EFI_STATUS
(EFIAPI *EFI_PCI_IO_PROTOCOL_CONFIG) (
IN EFI_PCI_IO_PROTOCOL
*This,
IN EFI_PCI_IO_PROTOCOL_WIDTH Width,
IN UINT32 Offset,
IN UINTN Count,
IN OUT VOID *Buffer
);
Parameters
This A pointer to the EFI_PCI_IO_PROTOCOL instance. Type
EFI_PCI_IO_PROTOCOL is defined in Section 12.4.
Width Signifies the width of the memory operations. Type
EFI_PCI_IO_PROTOCOL_WIDTH is defined in Section 12.4.
Offset The offset within the PCI configuration space for the PCI
controller.
Count The number of PCI configuration operations to perform. Bytes
moved is
Width size * Count , starting at Offset .
Buffer For read operations, the destination buffer to store the results. For
write operations, the source buffer to write data from.