keyboard.c

#include "keyboard.h"
#include "idt.h"
#include "pic.h"
#include "vga.h"

#define KB_DATA_PORT    0x60
#define KB_STATUS_PORT  0x64

/* US QWERTY scancode set 1 — 0 = non-printable */
static const char sc_ascii[58] = {
    0, 0,
    '1','2','3','4','5','6','7','8','9','0','-','=','\b',
    '\t','q','w','e','r','t','y','u','i','o','p','[',']','\n',
    0,  /* left ctrl */
    'a','s','d','f','g','h','j','k','l',';','\'','`',
    0,  /* left shift */
    '\\','z','x','c','v','b','n','m',',','.','/',
    0,  /* right shift */
    '*',
    0,  /* alt */
    ' '
};

static const char sc_ascii_shift[58] = {
    0, 0,
    '!','@','#','$','%','^','&','*','(',')','_','+','\b',
    '\t','Q','W','E','R','T','Y','U','I','O','P','{','}','\n',
    0,
    'A','S','D','F','G','H','J','K','L',':','"','~',
    0,
    '|','Z','X','C','V','B','N','M','<','>','?',
    0,'*',0,' '
};

/* Ring buffer */
#define KB_BUF_SIZE 256
static volatile char     kb_buf[KB_BUF_SIZE];
static volatile uint32_t kb_head = 0;
static volatile uint32_t kb_tail = 0;

static uint8_t shift_held = 0;
static uint8_t caps_lock  = 0;

static void keyboard_irq_handler(registers_t *regs) {
    (void)regs;

    /* Always read the scancode to clear the interrupt */
    uint8_t sc = inb(KB_DATA_PORT);

    /* Key release */
    if (sc & 0x80) {
        uint8_t rel = sc & 0x7F;
        if (rel == 0x2A || rel == 0x36) shift_held = 0;
        return;
    }

    if (sc == 0x2A || sc == 0x36) { shift_held = 1; return; }
    if (sc == 0x3A)               { caps_lock = !caps_lock; return; }

    if (sc < 58 && sc_ascii[sc]) {
        char c = shift_held ? sc_ascii_shift[sc] : sc_ascii[sc];
        if (caps_lock) {
            if (c >= 'a' && c <= 'z') c -= 32;
            else if (c >= 'A' && c <= 'Z') c += 32;
        }
        uint32_t next = (kb_head + 1) % KB_BUF_SIZE;
        if (next != kb_tail) {
            kb_buf[kb_head] = c;
            kb_head = next;
        }
    }
}

void keyboard_init(void) {
    /* Drain stale bytes from keyboard controller before enabling IRQ */
    while (inb(KB_STATUS_PORT) & 0x01)
        inb(KB_DATA_PORT);

    idt_register_handler(33, keyboard_irq_handler);
    pic_unmask_irq(1);
}

char keyboard_poll(void) {
    if (kb_head == kb_tail) return 0;
    char c = kb_buf[kb_tail];
    kb_tail = (kb_tail + 1) % KB_BUF_SIZE;
    return c;
}

char keyboard_getchar(void) {
    char c;
    while (!(c = keyboard_poll()))
        __asm__ volatile ("hlt");
    return c;
}