From e4200782ac9017bbe7c3f90b2668e7d513785158 Mon Sep 17 00:00:00 2001
From: Mathieu Maret <mathieu.maret@gmail.com>
Date: Thu, 8 Nov 2018 21:11:45 +0100
Subject: [PATCH] Add Serial driver

---
 core/irq_handler.c |  7 ++++++
 core/main.c        |  4 ++++
 drivers/serial.c   | 55 ++++++++++++++++++++++++++++++++++++++++++++++
 drivers/serial.h   |  6 +++++
 4 files changed, 72 insertions(+)
 create mode 100644 drivers/serial.c
 create mode 100644 drivers/serial.h

diff --git a/core/irq_handler.c b/core/irq_handler.c
index 971f699..2d8dda4 100644
--- a/core/irq_handler.c
+++ b/core/irq_handler.c
@@ -3,6 +3,7 @@
 #include "irq.h"
 #include "keyboard.h"
 #include "pic.h"
+#include "serial.h"
 #include "vga.h"
 
 // Need GCC > 6
@@ -20,3 +21,9 @@ __attribute__((interrupt)) void timer_handler(struct interrupt_frame *frame)
         printIntDetails(timeCnt++, RED, BLACK, 20, VGA_HEIGHT - 1);
         (void)frame;
 }
+
+__attribute__((interrupt)) void serial_handler(struct interrupt_frame *frame)
+{
+        EOIIrq(IRQ_COM1);
+        serial_do_irq((int)frame);
+}
diff --git a/core/main.c b/core/main.c
index b1ac5da..131c35f 100644
--- a/core/main.c
+++ b/core/main.c
@@ -8,6 +8,7 @@
 #include "mem.h"
 #include "multiboot.h"
 #include "pit.h"
+#include "serial.h"
 #include "stdarg.h"
 #include "vga.h"
 
@@ -61,6 +62,9 @@ void kmain(unsigned long magic, unsigned long addr)
     exceptionSetRoutine(EXCEPTION_DOUBLE_FAULT, print_handler);
     // Enabling the HW interrupts
     asm volatile("sti\n");
+    printf("Init Serial\n");
+    initSerial(115200);
+
     int count = 0;
     while (1) {
         printIntDetails(count++, GREEN, BLACK, 0, VGA_HEIGHT - 1);
diff --git a/drivers/serial.c b/drivers/serial.c
new file mode 100644
index 0000000..b398b71
--- /dev/null
+++ b/drivers/serial.c
@@ -0,0 +1,55 @@
+#include "serial.h"
+#include "io.h"
+#include "irq.h"
+
+#define PORT 0x3f8 /* COM1 */
+#define SERIAL_MAX_SPEED 115200
+
+/* The type of parity.  */
+#define UART_NO_PARITY 0x00
+#define UART_ODD_PARITY 0x08
+#define UART_EVEN_PARITY 0x18
+
+/* The type of word length.  */
+#define UART_5BITS_WORD 0x00
+#define UART_6BITS_WORD 0x01
+#define UART_7BITS_WORD 0x02
+#define UART_8BITS_WORD 0x03
+
+/* The type of the length of stop bit.  */
+#define UART_1_STOP_BIT 0x00
+#define UART_2_STOP_BITS 0x04
+
+void initSerial(int speed)
+{
+   unsigned short div = SERIAL_MAX_SPEED / speed;
+   outb(PORT + 1, 0x00);       // Disable all interrupts
+   outb(PORT + 3, 0x80);       // Enable DLAB (set baud rate divisor)
+   outb(PORT + 0, div & 0xFF); // Set divisor lo byte
+   outb(PORT + 1, div >> 8);   // Set divisor hi byte
+   outb(PORT + 3,
+        UART_NO_PARITY | UART_8BITS_WORD | UART_1_STOP_BIT); // 8 bits, no parity, one stop bit
+   outb(PORT + 2, 0xC7); // Enable FIFO, clear them, with 14-byte threshold
+   outb(PORT + 4, 0x0B); // IRQs enabled, RTS/DSR set
+}
+
+int isTransmitEmpty()
+{
+   return inb(PORT + 5) & 0x20;
+}
+
+void writeSerial(char a)
+{
+   while (isTransmitEmpty() == 0)
+      ;
+
+   outb(PORT, a);
+}
+
+void serial_do_irq(int level){
+   if(level == IRQ_COM1){
+      char c = inb(PORT + 5) & 1;
+      writeSerial(c);
+   }
+   return;
+}
diff --git a/drivers/serial.h b/drivers/serial.h
new file mode 100644
index 0000000..0389b71
--- /dev/null
+++ b/drivers/serial.h
@@ -0,0 +1,6 @@
+#pragma once
+
+
+void initSerial(int speed);
+void writeSerial(char a);
+void serial_do_irq(int level);