From b0b557d919848e2d585c52f064b3f6918a333533 Mon Sep 17 00:00:00 2001
From: Max Wash <mbswash@gmail.com>
Date: Wed, 8 Feb 2023 21:28:14 +0000
Subject: [PATCH] x86_64: add temporary serial driver for printk

---
 arch/x86_64/include/arch/serial.h | 17 +++++++++++++++++
 arch/x86_64/serial.c              | 30 ++++++++++++++++++++++++++++++
 arch/x86_64/vgacon.c              |  3 +++
 3 files changed, 50 insertions(+)
 create mode 100644 arch/x86_64/include/arch/serial.h
 create mode 100644 arch/x86_64/serial.c

diff --git a/arch/x86_64/include/arch/serial.h b/arch/x86_64/include/arch/serial.h
new file mode 100644
index 0000000..f19f226
--- /dev/null
+++ b/arch/x86_64/include/arch/serial.h
@@ -0,0 +1,17 @@
+#ifndef ARCH_SERIAL_H_
+#define ARCH_SERIAL_H_
+
+#define SERIAL_PORT_A 0x3F8
+#define SERIAL_PORT_B 0x2F8
+#define SERIAL_PORT_C 0x3E8
+#define SERIAL_PORT_D 0x2E8
+
+extern void serial_putchar(int port, char ch);
+
+extern void serial_wait(int device);
+extern void serial_send_byte(int device, char out);
+extern char serial_recv_byte(int device);
+
+extern int serial_rcvd(int device);
+
+#endif
diff --git a/arch/x86_64/serial.c b/arch/x86_64/serial.c
new file mode 100644
index 0000000..0c2d666
--- /dev/null
+++ b/arch/x86_64/serial.c
@@ -0,0 +1,30 @@
+#include <arch/serial.h>
+#include <arch/ports.h>
+
+static int transmit_empty(int device)
+{
+    return inportb(device + 5) & 0x20;
+}
+
+void serial_send_byte(int device, char out)
+{
+    unsigned int _count = 0;
+    while (!transmit_empty(device)) {
+        _count++;
+    }
+
+    outportb(device, out);
+
+    while (!transmit_empty(device)) {
+        _count++;
+    }
+}
+
+void serial_putchar(int port, char ch)
+{
+    if (ch == '\n') {
+        serial_send_byte(port, '\r');
+    }
+
+    serial_send_byte(port, ch);
+}
diff --git a/arch/x86_64/vgacon.c b/arch/x86_64/vgacon.c
index 4b15123..d511540 100644
--- a/arch/x86_64/vgacon.c
+++ b/arch/x86_64/vgacon.c
@@ -1,3 +1,4 @@
+#include <arch/serial.h>
 #include <socks/libc/string.h>
 #include <socks/libc/ctype.h>
 #include <arch/ports.h>
@@ -75,6 +76,8 @@ static void handle_ctrl(int c)
 
 static void vgacon_putchar(int c)
 {
+	serial_putchar(SERIAL_PORT_A, c);
+
 	if (iscntrl(c)) {
 		handle_ctrl(c);
 		return;