#define PIC1 0x20 /* IO base address for master PIC */

#define PIC2 0xa0 /* IO base address for slave PIC */

#define PIC1_COMMAND PIC1

#define PIC1_DATA (PIC1 1)

#define PIC2_COMMAND PIC2

#define PIC2_DATA (PIC2 1)

#define ICW1_ICW4 0x01

#define ICW1_INIT 0x10

#define ICW4_8086 0x01

/* look at it carefully! */

void outb(unsigned char value, unsigned short port);

/* init PIC and remap the irqs */

void pic_remap(int offset1, int offset2) {

unsigned char m1, m2;

// save masks

m1 = inb(PIC1_DATA);

m2 = inb(PIC2_DATA);

// start the initialization sequence

outb(ICW1_ICW4 | ICW1_INIT, PIC1_COMMAND);

outb(ICW1_ICW4 | ICW1_INIT, PIC2_COMMAND);

// ICW2: master PIC vector offset

outb((unsigned char)offset1, PIC1_DATA);

// ICW2: slave PIC vector offset

outb((unsigned char)offset2, PIC2_DATA);

// ICW3: tell master PIC what irq is connected slave PIC, 80x86 use irq line 2

outb(4, PIC1_DATA);

// ICW3: tell slave PIC the same thing, but use a different notation

outb(2, PIC2_DATA);

// ICW4: set how the pic operates

outb(ICW4_8086, PIC1_DATA);

outb(ICW4_8086, PIC2_DATA);

// restore masks

outb(m1, PIC1_DATA);

outb(m2, PIC2_DATA);

}