From 59f86fe8dd237e50c7fea03b506125e3abff0157 Mon Sep 17 00:00:00 2001
From: Aleksa Vuckovic <aleksav013@gmail.com>
Date: Mon, 5 Sep 2022 04:19:56 +0200
Subject: serial output

---
 kernel/src/devices/serial.c | 37 +++++++++++++++++++++++++++++++++++++
 kernel/src/libk/stdio.c     |  5 ++++-
 kernel/src/main.c           |  2 ++
 3 files changed, 43 insertions(+), 1 deletion(-)
 create mode 100644 kernel/src/devices/serial.c

(limited to 'kernel/src')

diff --git a/kernel/src/devices/serial.c b/kernel/src/devices/serial.c
new file mode 100644
index 0000000..76bc71a
--- /dev/null
+++ b/kernel/src/devices/serial.c
@@ -0,0 +1,37 @@
+#include <io.h>
+#include <serial.h>
+
+void init_serial()
+{
+	outb(PORT + 1, 0x00);	// Disable all interrupts
+	outb(PORT + 3, 0x80);	// Enable DLAB (set baud rate divisor)
+	outb(PORT + 0, 0x03);	// Set divisor to 3 (lo byte) 38400 baud
+	outb(PORT + 1, 0x00);	//                  (hi byte)
+	outb(PORT + 3, 0x03);	// 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
+}
+
+uint8_t serial_received()
+{
+	return inb(PORT + 5) & 1;
+}
+
+char read_serial()
+{
+	while (serial_received() == 0);
+
+	return (char)inb(PORT);
+}
+
+uint8_t is_transmit_empty()
+{
+	return inb(PORT + 5) & 0x20;
+}
+
+void write_serial(char c)
+{
+	while (is_transmit_empty() == 0);
+
+	outb(PORT, (uint8_t)c);
+}
diff --git a/kernel/src/libk/stdio.c b/kernel/src/libk/stdio.c
index da5d839..61681f0 100644
--- a/kernel/src/libk/stdio.c
+++ b/kernel/src/libk/stdio.c
@@ -1,9 +1,9 @@
 #include <types.h>
 #include <libk/stdio.h>
-
 #include <stdarg.h>
 #include <libk/string.h>
 #include <graphics.h>
+#include <serial.h>
 
 uint32_t curr_x;
 uint32_t curr_y;
@@ -19,6 +19,7 @@ inline void print_char(char c)
 		curr_y = 0;
 	}
 	if (c == '\n') {
+		write_serial('\n');
 		curr_x = 0;
 		curr_y++;
 		return;
@@ -31,6 +32,8 @@ inline void print_char(char c)
 	}
 	fb_draw_character(main_fb, c, (int32_t)curr_x * 8, (int32_t)curr_y * 16, WHITE, BLACK);
 	curr_x++;
+
+	write_serial(c);
 }
 
 inline void print_string(const char* s)
diff --git a/kernel/src/main.c b/kernel/src/main.c
index 45d2eeb..dce9c05 100644
--- a/kernel/src/main.c
+++ b/kernel/src/main.c
@@ -14,10 +14,12 @@
 #include <gdt.h>
 #include <userspace.h>
 #include <tss.h>
+#include <serial.h>
 
 int kernel_main(mb2_tag_header* multiboot_bootinfo, uint32_t multiboot_magic);
 int kernel_main(mb2_tag_header* multiboot_bootinfo, uint32_t multiboot_magic)
 {
+	init_serial();
 	init_gdt();
 	init_paging();
 	init_idt();
-- 
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