devices/pic_8259.c


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#include "pic.h"
#include <sys/io.h>

#define PIC1 0x20
#define PIC2 0xa0
#define DATA 1

// initialization
#define ICW1_INIT 0x10
// TODO
#define ICW1_ICW4 0x01
// 8086/88 mode
#define ICW4_8086 0x01

void
pic_init()
{
  outb(ICW1_INIT | ICW1_ICW4, PIC1);
  outb(ICW1_INIT | ICW1_ICW4, PIC2);

  outb(0x20, PIC1 + DATA); // offset 0x20
  outb(0x28, PIC2 + DATA); // offset 0x28

  outb(0x04, PIC1 + DATA); // tell master pic there is a slave pic
  outb(0x02, PIC2 + DATA); // tell slave pic its cascade identity

  outb(ICW4_8086, PIC1 + DATA);
  outb(ICW4_8086, PIC2 + DATA);

  // PIC masks
  outb(0xff, PIC1 + DATA);
  outb(0xff, PIC2 + DATA);
}

void
pic_clear(unsigned char irq)
{
  outb(0x20, PIC1);
}