hazel/kernel/pit.c

#include <kernel/kernel.h>
#include <kernel/pit.h>
#include <kernel/io.h>
#include <kernel/pic.h>

extern kernel_ctx_t ctx;

void pit_init(void) {
    outb(PIT_MODE_CMD, PIT_CHAN0 | PIT_LOHIGH | PIT_MODE2);

    outb(PIT_CHAN0_DATA, (uint8_t)(DIVISOR & 0xff));
    outb(PIT_CHAN0_DATA, (uint8_t)((DIVISOR & 0xff00) >> 8));
}

extern void task_switch(task_t *task);

int pit_handler(void) {
    ctx.ticks++;

    outb(PIT_CHAN0_DATA, (uint8_t)(DIVISOR & 0xff));
    outb(PIT_CHAN0_DATA, (uint8_t)((DIVISOR & 0xff00) >> 8));
    pic_send_eoi(0);

    if ((ctx.ticks % 3) == 0) return 1;
    else return 0;
}