Sending data (debug printing) to serial port

src/kernel/include/ports.h

@@ -0,0 +1,17 @@
+#pragma once
+#include <stdint.h>
+
+static __inline void _outb(uint16_t port, uint8_t value)
+{
+  asm volatile("outb %1, %0" : : "dN" (port), "a" (value));
+}
+
+static __inline uint8_t _inb(uint16_t port)
+{
+  uint8_t ret;
+  asm volatile("inb %1, %0" : "=a" (ret) : "dN" (port));
+  return ret;
+}
+
+#define outb _outb
+#define inb _inb

src/kernel/include/serial.h

@@ -0,0 +1,7 @@
+#pragma once
+#include <stdint.h>
+
+#define PORT_COM1 0x3F8
+
+void serial_init(uint16_t port);
+void serial_write(uint16_t port, uint8_t c);