#include "pic.h"
#include "port_io.h"

#define PIC1_COMMAND 0x20
#define PIC1_DATA    0x21
#define PIC2_COMMAND 0xA0
#define PIC2_DATA    0xA1

#define ICW1_ICW4       0x01        /* ICW4 (not) needed */
#define ICW1_SINGLE     0x02        /* Single (cascade) mode */
#define ICW1_INTERVAL4  0x04        /* Call address interval 4 (8) */
#define ICW1_LEVEL      0x08        /* Level triggered (edge) mode */
#define ICW1_INIT       0x10        /* Initialization - required! */

#define ICW4_8086       0x01        /* 8086/88 (MCS-80/85) mode */
#define ICW4_AUTO       0x02        /* Auto (normal) EOI */
#define ICW4_BUF_SLAVE  0x08        /* Buffered mode/slave */
#define ICW4_BUF_MASTER 0x0C        /* Buffered mode/master */
#define ICW4_SFNM       0x10        /* Special fully nested (not) */

#define PIC_EOI         0x20

void pic_send_eoi(uint8_t irq)
{
    if(irq >= 8)
        outb(PIC2_COMMAND, PIC_EOI);
    
    outb(PIC1_COMMAND, PIC_EOI);
}

/*
    reinitialize the PIC controllers, giving them specified vector offsets
    rather than 8h and 70h, as configured by default
*/
#define PIC1_OFFSET 0x20
#define PIC2_OFFSET 0x28

void init_pic(void)
{
    unsigned char a1, a2;

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

    outb(PIC1_COMMAND, ICW1_INIT | ICW1_ICW4);  // starts the initialization 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 there is 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, a1);   // restore saved masks.
    outb(PIC2_DATA, a2);
}

void pic_clear_mask(uint8_t irq) {
    uint16_t port;
    uint8_t value;
 
    if(irq < 8) {
        port = PIC1_DATA;
    } else {
        port = PIC2_DATA;
        irq -= 8;
    }
    value = inb(port) & ~(1 << irq);
    outb(port, value);
}

void pic_set_mask(uint8_t irq) {
    uint16_t port;
    uint8_t value;
 
    if(irq < 8) {
        port = PIC1_DATA;
    } else {
        port = PIC2_DATA;
        irq -= 8;
    }
    value = inb(port) | (1 << irq);
    outb(port, value);
}