kfs: added the serial print

* 38400 bauds
* 1 stop bit
* no parity check
* 8 bits words

Signed-off-by: Olivier Gayot <duskcoder@gmail.com>

1 files changed, 57 insertions, 0 deletions

diff --git a/src/serial.c b/src/serial.c
new file mode 100644
index 0000000..720d454
--- /dev/null
+++ b/src/serial.c
@@ -0,0 +1,57 @@
+#define COM1_BASE 0x3f8
+#define COM2_BASE 0x2f8
+#define COM3_BASE 0x3e8
+#define COM4_BASE 0x2e8
+
+#include "uart_16550.h"
+
+static inline void outb(unsigned char value, unsigned short port)
+{
+    asm volatile("outb %0,%1" : : "a" (value), "dN" (port));
+}
+
+static inline unsigned char inb(unsigned short port)
+{
+    unsigned char value;
+
+    asm volatile("inb %1,%0" : "=a" (value) : "dN" (port));
+
+    return value;
+}
+
+int serial_putchar(unsigned char c)
+{
+    outb(c, COM1_BASE);
+
+    return 1;
+}
+
+int serial_init(void)
+{
+    /* set the communication parameters */
+    unsigned char lcr_value = 0x0;
+
+    lcr_value = DATA_WORD_LEN_8
+        | STOP_BIT_1
+        | PARITY_NONE
+        | BREAK_SIGNAL_DISABLED
+        | DLAB_ACCESSIBLE_DLL_DLM;
+
+    outb(lcr_value, COM1_BASE + 3);
+
+    unsigned char dll_value = 0x03;
+    unsigned char dlm_value = 0x00;
+
+    outb(dll_value, COM1_BASE + 0);
+    outb(dlm_value, COM1_BASE + 1);
+
+    lcr_value = DATA_WORD_LEN_8
+        | STOP_BIT_1
+        | PARITY_NONE
+        | BREAK_SIGNAL_DISABLED
+        | DLAB_ACCESSIBLE_RBR_THR_IER;
+
+    outb(lcr_value, COM1_BASE + 3);
+
+    return 0;
+}