PCI Bus Driver

Peripheral Component Interconnect Device Enumeration

Overview

The PCI driver enumerates and configures devices on the PCI bus. Modern hardware connects via PCI, including network cards, AHCI storage controllers, and graphics cards.

PCI Configuration Space

Each PCI device has 256 bytes of configuration space accessible via I/O ports or memory-mapped I/O. AOS uses the port-based method:

Port	Purpose
0xCF8	Address register (write device address)
0xCFC	Data register (read/write 32-bit data)

Device Enumeration

The kernel scans all PCI buses and devices:

1. For each bus (0-255)
2. For each device on bus (0-31)
3. For each function (0-7)
4. Read vendor/device ID
5. If valid, record device info
6. Initialize appropriate driver

Key Takeaways