matos/drivers/pic.c

#include "pic.h"
#include "io.h"
#include "irq.h"

#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) */

void initPic(void)
{
    /* Send CMD: Init + sequence in 4 DATA */
    outb(PIC_MASTER_CMD, ICW1_INIT + ICW1_ICW4);
    outb(PIC_SLAVE_CMD, ICW1_INIT + ICW1_ICW4);

    /* Send ICW2: ctrl base address. Remap IRQ from interupt range 0x0-0xF to 0x20-0x2F as
     * intel
     * reserve interupt 0x0-0x1F in protected mode (e.g. 0-7 are CPU exception)  */
    outb(PIC_MASTER_DATA, IRQ_INTERRUPT_BASE_ADDRESS);
    outb(PIC_SLAVE_DATA, IRQ_INTERRUPT_BASE_ADDRESS + 8);

    /* Send ICW3 master: mask where slaves are connected */
    outb(PIC_MASTER_DATA, 0x4);
    /* Send ICW3 slave: index where the slave is connected on master */
    outb(PIC_SLAVE_DATA, 0x2);

    /* Send ICW4: 8086 mode, fully nested, not buffered, no implicit EOI */
    outb(PIC_MASTER_DATA, ICW4_8086);
    outb(PIC_SLAVE_DATA, ICW4_8086);

    /* Send OCW1:
     * Closing all IRQs : waiting for a correct handler The only IRQ
     * enabled is the cascade (that's why we use 0xFB for the master) */
    outb(PIC_MASTER_DATA, 0xFB);
    outb(PIC_SLAVE_DATA, 0xFF);
}

inline void EOIIrq(int irq)
{
    if (irq >= 8)
        outb(PIC_SLAVE_CMD, PIC_EOI);

    outb(PIC_MASTER_CMD, PIC_EOI);
}

void disableIrq(int irq)
{
    if (irq < 8) {
        uint8_t status = inb(PIC_MASTER_DATA);
        outb(PIC_MASTER_DATA, (status | (1 << irq)));
    } else {
        uint8_t status = inb(PIC_SLAVE_DATA);
        outb(PIC_SLAVE_DATA, (status | (1 << (irq - 8))));
    }
}

void enableIrq(int irq)
{
    if (irq < 8) {
        uint8_t status = inb(PIC_MASTER_DATA);
        outb(PIC_MASTER_DATA, (status & ~(1 << irq)));
    } else {
        uint8_t status = inb(PIC_SLAVE_DATA);
        outb(PIC_SLAVE_DATA, (status & ~(1 << (irq - 8))));
    }
}