rockOS/kernel/arch/i386/boot/pic.c

#include <kernel/pic.h>
#include <stdio.h>

void PIC_remap() {
    printf("Beginning PIC initialization.\n");
    
    unsigned char a1, a2;

    a1 = inb(PIC1_DATA); // save masks
    a2 = inb(PIC2_DATA);

    outb(PIC1_COMMAND, ICW1_INIT | ICW1_ICW4); // Start init sequence in cascade mode
    io_wait();
    outb(PIC2_COMMAND, ICW1_INIT | ICW1_ICW4);
    io_wait();

    outb(PIC1_DATA, PIC1_OFFSET); // ICW2: Master PIC vector offset
    io_wait();
    outb(PIC2_DATA, PIC2_OFFSET); // ICW2: Slave PIC vector offset
    io_wait();
    outb(PIC1_DATA, 4); // ICW3: tell Master PIC that theres a slave PIC at IRQ2 (0000 0100)
    io_wait();
    outb(PIC2_DATA, 2); // ICW3: tell Slave PIC its cascade identity (0000 0010)
    io_wait();

    outb(PIC1_DATA, ICW4_8086);
    io_wait();
    outb(PIC2_DATA, ICW4_8086);
    io_wait();

    outb(PIC1_DATA, 0xFF); // restore saved masks
    outb(PIC2_DATA, 0xFF);

    outb(PIC1_DATA, 0xFD); // Keyboard IRQ
    //outb(PIC2_DATA, 0xFF);
}