Add UART module

include/config.h

@@ -2,5 +2,6 @@
 #define CONFIG_H_
 
 #define KSTACK_BASE 0x88000000
+#define UART0_BASE 0x10000000
 
 #endif // CONFIG_H_

include/uart.h

@@ -0,0 +1,6 @@
+#ifndef UART_H_
+#define UART_H_
+
+void uart_putc(char c);
+
+#endif // UART_H_

src/kmain.c

@@ -1,12 +1,11 @@
 #include <attribs.h>
 #include <types.h>
+#include <uart.h>
 
 noreturn void kmain(void) {
-    volatile u8 *uart = (volatile u8 *) 0x10000000;
     const char *s = "Hello, world!\n";
-
     for (int i = 0; s[i] != '\0'; i++)
-        *uart = s[i];
+        uart_putc(s[i]);
 
     while (true)
         ;

src/uart.c

@@ -0,0 +1,27 @@
+#include <attribs.h>
+#include <config.h>
+#include <types.h>
+
+#define UART_RBR 0
+#define UART_THR 0
+#define UART_DLL 0
+#define UART_IER 1
+#define UART_DLM 1
+#define UART_IIR 2
+#define UART_FCR 2
+#define UART_LCR 3
+#define UART_MCR 4
+#define UART_LSR 5
+#define UART_MSR 6
+#define UART_SCR 7
+
+#define UART_LSR_THRE 0x20
+
+#define uart_read_reg(reg) *((volatile u8 *) UART0_BASE + reg)
+#define uart_write_reg(reg, val) *((volatile u8 *) UART0_BASE + reg) = val
+
+void uart_putc(char c) {
+    while (!(uart_read_reg(UART_LSR) & UART_LSR_THRE))
+        ;
+    uart_write_reg(UART_THR, c);
+}