#include "../includes/pic.h"
#include "../includes/io.h"
#include "../includes/idt.h"
#include "../includes/irq.h"

#define PIC1_PORT 				0x20
#define PIC1_DATA_PORT			0X21
#define PIC2_PORT 				0xA0
#define PIC2_DATA_PORT			0XA1

#define PIC1_START_INTERRUPT 	0x20
#define PIC2_START_INTERRUPT 	0x28
#define PIC2_END_INTERRUPT   	PIC2_START_INTERRUPT + 7

#define PIC_ACK 				0x20

void pic_acknowledge(unsigned int interrupt_no)
{
	if (interrupt_no < PIC2_START_INTERRUPT)
		outb(PIC1_PORT, PIC_ACK);
	else
		outb(PIC2_PORT, PIC_ACK);
}

void setup_pics(void)
{
	// The PIC uses Initialization Command Words (ICW) to communicate.
	// So we start with the first ICW, 0x11, this tells the PIC to expect 
	// 3 more ICWs.
	outb(PIC1_PORT, 0x11);
	outb(PIC2_PORT, 0x11);
	
	// This tells the pic what offset to use when it generates the interrupt numbers.
	// Since the first 32 ISRs are reserved by the CPU we must start at IRS32 and work
	// our way up. When the PIC recieves an interrupt on it's input line, it will add
	// the supplied values to that number before sending the newly made number to the CPU.
	// Thereby remapping an interrupt number that would have normally conflicted with the 
	// values in the IDT.
	outb(PIC1_DATA_PORT, PIC1_START_INTERRUPT);
	outb(PIC2_DATA_PORT, PIC2_START_INTERRUPT);
	
	// This ICW allows for cascading of their outputs to inputs between each other.
	// I'm not sure what that really means but at this current time I'm not going to
	// be doing this, so the bits will all be set to zero.
	outb(PIC1_DATA_PORT, 0x00);
	outb(PIC2_DATA_PORT, 0x00);
	
	// This is the environment info, and setting the lowest bit tells the PICs
	// that we're running in 80x86 mode.
	outb(PIC1_DATA_PORT, 0x01);
	outb(PIC2_DATA_PORT, 0x01);
	
	// Finally, we have the interrupt masks.
	outb(PIC1_DATA_PORT, 0xFF);
	outb(PIC2_DATA_PORT, 0xFF);
	
	idt_set_gate(33, (unsigned long) &irq1, 0x08, 0x8E);
}