sound.c

#include "types.h"

static inline uint8_t inb(uint16_t port) {
    uint8_t ret;
    __asm__ __volatile__ ("inb %1, %0" : "=a"(ret) : "Nd"(port));
    return ret;
}

static inline void outb(uint16_t port, uint8_t val) {
    __asm__ __volatile__ ("outb %0, %1" : : "a"(val), "Nd"(port));
}

void play_sound(uint32_t frequency) {
    uint32_t divisor = 1193182 / frequency;
    outb(0x43, 0xB6);
    outb(0x42, (uint8_t)(divisor & 0xFF));
    outb(0x42, (uint8_t)((divisor >> 8) & 0xFF));

    uint8_t tmp = inb(0x61);
    if (tmp != (tmp | 3)) {
        outb(0x61, tmp | 3);
    }
}

void nosound(void) {
    uint8_t tmp = inb(0x61) & 0xFC;
    outb(0x61, tmp);
}

void beep(void) {
    play_sound(750);
    for (volatile uint32_t i = 0; i < 50000000; i++);
    nosound();
}