Sending data (debug printing) to serial port

src/kernel/boot/debug.c

@@ -1,11 +1,10 @@
 #include <stddef.h>
 #include <stdarg.h>
 #include <stdint.h>
+#include <serial.h>
 
 // TODO: Temporary declarations
 void vga_write(char c);
-void serial_write(int port, char c);
-#define PORT_COM1 0
 
 
 void num2str(char *buf, uint64_t num, uint64_t base)

src/kernel/boot/debug.tt

@@ -20,11 +20,11 @@ void vga_write(char c)
   static int i = 0;
   vga_recv[i++] = c;
 }
-void serial_write(int port, char c)
+void serial_write(uint16_t port, uint8_t c)
 {
   (void)port;
   static int i = 0;
-  serial_recv[i++] = c;
+  serial_recv[i++] = (char)c;
 }
 
 TEST(putch_sends_character_to_vga)

src/kernel/boot/kmain.c

@@ -1,4 +1,6 @@
 #include <memory.h>
+#include <serial.h>
+#include <debug.h>
 
 void clear_screen()
 {
@@ -17,10 +19,20 @@ void print_string(char *str)
   }
 }
 
+void vga_write(char c)
+{
+// TODO: DUMMY
+  (void)c;
+}
+
 void kmain()
 {
   clear_screen();
   print_string("Hello from c, world!");
+
+  serial_init(PORT_COM1);
+  debug_printf("Hello from debug printing function!\n");
+  debug_printf("A number:%d\n", 12345);
   for(;;);
 }
 

src/kernel/drivers/serial.c

@@ -0,0 +1,19 @@
+#include <serial.h>
+#include <ports.h>
+
+void serial_init(uint16_t port)
+{
+  outb(port + 1, 0x00);
+  outb(port + 3, 0x80);
+  outb(port + 0, 0x03);
+  outb(port + 1, 0x00);
+  outb(port + 3, 0x03);
+  outb(port + 2, 0xC7);
+  outb(port + 4, 0x0B);
+}
+
+void serial_write(uint16_t port, uint8_t c)
+{
+  while(!(inb(port + 5)&0x20));
+  outb(port, c);
+}

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);