feat(drivers): add PS/2 keyboard driver

include/keyboard.h

@@ -0,0 +1,11 @@
+#ifndef FROSTBYTE_KEYBOARD_H
+#define FROSTBYTE_KEYBOARD_H
+
+#include "types.h"
+
+void keyboardInit(void);
+void keyboardHandler(void);
+bool keyboardHasChar(void);
+char keyboardReadChar(void);
+
+#endif

src/keyboard.c

@@ -0,0 +1,77 @@
+#include "keyboard.h"
+#include "ports.h"
+
+#define keyboardData 0x60
+
+static const char scancodeLower[128] = {
+    0, 27, '1', '2', '3', '4', '5', '6', '7', '8', '9', '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, ' ', 0
+};
+
+static const char scancodeUpper[128] = {
+    0, 27, '!', '@', '#', '$', '%', '^', '&', '*', '(', ')', '_', '+', '\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, ' ', 0
+};
+
+#define keyBufferSize 128
+static volatile char keyBuffer[keyBufferSize];
+static volatile uint32 bufferHead;
+static volatile uint32 bufferTail;
+static bool shiftHeld;
+
+void keyboardInit(void)
+{
+    bufferHead = 0;
+    bufferTail = 0;
+    shiftHeld = false;
+}
+
+static void pushChar(char c)
+{
+    uint32 next = (bufferHead + 1) % keyBufferSize;
+    if (next != bufferTail) {
+        keyBuffer[bufferHead] = c;
+        bufferHead = next;
+    }
+}
+
+void keyboardHandler(void)
+{
+    uint8 scancode = inb(keyboardData);
+
+    if (scancode == 0x2A || scancode == 0x36) {
+        shiftHeld = true;
+        return;
+    }
+    if (scancode == 0xAA || scancode == 0xB6) {
+        shiftHeld = false;
+        return;
+    }
+    if (scancode & 0x80)
+        return;
+
+    char c = shiftHeld ? scancodeUpper[scancode] : scancodeLower[scancode];
+    if (c)
+        pushChar(c);
+}
+
+bool keyboardHasChar(void)
+{
+    return bufferHead != bufferTail;
+}
+
+char keyboardReadChar(void)
+{
+    while (bufferHead == bufferTail)
+        __asm__ volatile("sti; hlt");
+
+    char c = keyBuffer[bufferTail];
+    bufferTail = (bufferTail + 1) % keyBufferSize;
+    return c;
+}