From 184f1fc5d716729b210af0127f2e5b4b00f094a8 Mon Sep 17 00:00:00 2001
From: ChUrl <christoph.urlacher@protonmail.com>
Date: Sat, 16 Jul 2022 00:57:17 +0200
Subject: [PATCH] add simple serial output

---
 c_os/user/devices/SerialOut.cc | 51 ++++++++++++++++++++++++++++++++++
 c_os/user/devices/SerialOut.h  | 28 +++++++++++++++++++
 2 files changed, 79 insertions(+)
 create mode 100644 c_os/user/devices/SerialOut.cc
 create mode 100644 c_os/user/devices/SerialOut.h

diff --git a/c_os/user/devices/SerialOut.cc b/c_os/user/devices/SerialOut.cc
new file mode 100644
index 0000000..13e20da
--- /dev/null
+++ b/c_os/user/devices/SerialOut.cc
@@ -0,0 +1,51 @@
+#include "user/devices/SerialOut.h"
+#include "kernel/Globals.h"
+
+int SerialOut::init() const {
+    // NOTE: I could add different ports for every register but this was easier as it's that way on OSDev
+    com1.outb(1, 0x00);  // Disable all interrupts
+    com1.outb(3, 0x80);  // Enable DLAB (set baud rate divisor)
+    com1.outb(0x03);     // Set divisor to 3 (lo byte) 38400 baud
+    com1.outb(1, 0x00);  //                  (hi byte)
+    com1.outb(3, 0x03);  // 8 bits, no parity, one stop bit
+    com1.outb(2, 0xC7);  // Enable FIFO, clear them, with 14-byte threshold
+    com1.outb(4, 0x0B);  // IRQs enabled, RTS/DSR set
+    com1.outb(4, 0x1E);  // Set in loopback mode, test the serial chip
+    com1.outb(0xAE);     // Test serial chip (send byte 0xAE and check if serial returns same byte)
+
+    // Check if serial is faulty (i.e: not same byte as sent)
+    if (com1.inb() != 0xAE) {
+        return 1;
+    }
+
+    // If serial is not faulty set it in normal operation mode
+    // (not-loopback with IRQs enabled and OUT#1 and OUT#2 bits enabled)
+    com1.outb(4, 0x0F);
+    return 0;
+}
+
+int SerialOut::serial_received() {
+    return com1.inb(5) & 1;
+}
+
+int SerialOut::is_transmit_empty() {
+    return com1.inb(5) & 0x20;
+}
+
+char SerialOut::read() {
+    while (serial_received() == 0) {}
+    return com1.inb();
+}
+
+void SerialOut::write(char a) {
+    while (is_transmit_empty() == 0) {}
+    com1.outb(a);
+}
+
+void SerialOut::write(char* a) {
+    char* current = a;
+    do {
+        this->write(*current);
+        current = current + 1;
+    } while (*current != '\0');
+}
diff --git a/c_os/user/devices/SerialOut.h b/c_os/user/devices/SerialOut.h
new file mode 100644
index 0000000..92939b6
--- /dev/null
+++ b/c_os/user/devices/SerialOut.h
@@ -0,0 +1,28 @@
+#ifndef __SerialOut_Include_H_
+#define __SerialOut_Include_H_
+
+#include "kernel/interrupts/ISR.h"
+#include "kernel/IOport.h"
+
+// NOTE: I took this code from https://wiki.osdev.org/Serial_Ports
+
+class SerialOut {
+private:
+    const IOport com1;
+
+    SerialOut(const SerialOut& copy) = delete;
+
+    int serial_received();
+    int is_transmit_empty();
+
+public:
+    SerialOut() : com1(0x3f8) {}
+
+    int init() const;
+
+    char read();
+    void write(char a);
+    void write(char* a);
+};
+
+#endif