Driver System

Driver Architecture

guideXOS drivers are compiled directly into the kernel image. All drivers initialize during boot and communicate directly with hardware through port I/O and memory-mapped I/O (MMIO).

Key Characteristics

• Statically Linked - All drivers compiled into kernel binary
• Direct Hardware Access - No HAL or abstraction layers
• Interrupt-Driven - Hardware events via IDT handlers
• DMA Capable - Direct Memory Access for network and storage
• Bare-Metal - Written in unsafe C# with pointer access

PCI Device Discovery

The PCI subsystem enumerates all devices on the PCI bus during initialization:

PCI Scan Process

PCI.Initialize()
    ↓
Scan Bus 0-255
    ↓ For each device:
    ├─ Read Vendor ID / Device ID
    ├─ Read Class Code / Subclass
    ├─ Read BAR (Base Address Registers)
    ├─ Enable Bus Mastering
    └─ Call device-specific Init()
        ├─ IDE Controller → IDE.Initialize()
        ├─ Network Card → Intel825xx.Initialize()
        ├─ USB Controller → (future support)
        └─ ...

PCI Configuration Space

Drivers use port I/O (0xCF8 / 0xCFC) to read/write PCI configuration registers:

// Read PCI config register
uint ReadConfig(byte bus, byte device, byte function, byte offset)
{
    uint address = 0x80000000 | (bus << 16) | (device << 11) 
                   | (function << 8) | (offset & 0xFC);
    Native.Out32(0xCF8, address);
    return Native.In32(0xCFC);
}

Detected Devices

Use the pci command in Console to view all detected PCI devices:

gx> pci
Bus:Dev.Fn  Vendor:Device  Class      Name
00:00.0     8086:1237      0600       Intel 440FX Chipset
00:01.0     8086:7000      0601       Intel PIIX3 ISA Bridge
00:01.1     8086:7010      0101       Intel PIIX3 IDE Controller
00:02.0     10EC:8139      0200       Realtek RTL8139 Fast Ethernet
00:03.0     1234:1111      0300       QEMU VGA

Storage Drivers

IDE/SATA Controller

guideXOS includes a legacy IDE driver for disk and CD-ROM access:

• PIO Mode - Programmed I/O transfer
• Primary/Secondary Channels - Master/Slave devices
• ATAPI Support - CD/DVD drives
• LBA Addressing - Supports large disks

Supported Operations

IDE.ReadSector(drive, lba, buffer)    // Read 512-byte sector
IDE.WriteSector(drive, lba, buffer)   // Write 512-byte sector
IDE.Identify(drive)                    // Get drive info
IDE.EjectCD(drive)                     // Eject CD tray

Port Layout

Network Drivers

guideXOS supports two families of network cards:

Intel 825xx Series

• Supported Cards: Intel PRO/1000 (82540EM, 82545EM, 82574L)
• DMA Engine: Descriptor ring buffers for TX/RX
• Interrupt Handling: Auto-clears on status read
• Link Detection: Automatic negotiation

// Intel 825xx TX/RX flow
Intel825xx.Send(packet[])
    ↓
Copy to TX descriptor ring
    ↓
Notify hardware (tail pointer)
    ↓
Hardware sends via DMA
    ↓
IRQ on completion

Realtek RTL8139/RTL8111

• Supported Cards: RTL8139 (older), RTL8111 (newer)
• Circular Buffers: 8KB RX buffer, 2KB TX buffer
• Low Resource Usage: Simple, reliable driver
• Wide Compatibility: Found in many VMs

// RTL8111 Packet Receive
Hardware writes to RX buffer
    ↓
Generate interrupt
    ↓
RTL8111.OnInterrupt()
    ↓
Copy packet from buffer
    ↓
Pass to IPv4 stack

MAC Address

Each driver reads the hardware MAC address from EEPROM or ROM registers. View your MAC with ipconfig.

Input Devices

PS/2 Keyboard

Standard PS/2 keyboard driver with scancode translation:

• Port: 0x60 (data), 0x64 (command)
• IRQ: IRQ1 (interrupt vector 0x21)
• Scancode Set: Set 1 (XT scancodes)
• Modifiers: Shift, Ctrl, Alt tracking

Keyboard.OnInterrupt()
    ↓
Read scancode from port 0x60
    ↓
Translate to ASCII/keycode
    ↓
Add to keyboard buffer
    ↓
GUI reads via Keyboard.GetKey()

PS/2 Mouse

PS/2 mouse with 3-byte packet protocol:

• Port: 0x60/0x64 (shared with keyboard)
• IRQ: IRQ12 (interrupt vector 0x2C)
• Protocol: 3-byte packets (buttons, X delta, Y delta)
• Wheel Support: Extended 4-byte packets

Graphics Drivers

VESA Framebuffer

guideXOS uses VESA BIOS Extensions for graphics:

• Resolution: 1024x768x32 (RGBA8888)
• Framebuffer: Memory-mapped linear buffer
• Double Buffering: Back buffer → front buffer copy
• Software Rendering: All drawing in C#

// Pixel drawing
void SetPixel(int x, int y, uint color)
{
    uint* fb = (uint*)framebufferAddress;
    fb[y * width + x] = color;
}

VGA Text Mode

VGA text mode (80x25) used during early boot:

• Buffer: 0xB8000 (memory-mapped)
• Format: 2 bytes per character (ASCII + attribute)
• Colors: 16 foreground, 8 background

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