Kernel: Add RTC to get current time

kernel/include/kernel/RTC.h

@@ -0,0 +1,20 @@
+#pragma once
+
+#include <stdint.h>
+
+namespace RTC
+{
+
+	struct Time
+	{
+		uint8_t	second;
+		uint8_t	minute;
+		uint8_t	hour;
+		uint8_t	day;
+		uint8_t	month;
+		int		year;
+	};
+
+	Time GetCurrentTime();
+
+}

kernel/kernel/RTC.cpp

@@ -0,0 +1,88 @@
+#include <kernel/IO.h>
+#include <kernel/RTC.h>
+
+#include <string.h>
+
+#define CURRENT_YEAR 2022
+
+#define CMOS_ADDRESS			0x70
+#define CMOS_DATA				0x71
+
+#define CMOS_REGISTER_SECOND	0x00
+#define CMOS_REGISTER_MINUTE	0x02
+#define CMOS_REGISTER_HOUR		0x04
+#define CMOS_REGISTER_WEEK_DAY	0x06
+#define CMOS_REGISTER_DAY		0x07
+#define CMOS_REGISTER_MONTH		0x08
+#define CMOS_REGISTER_YEAR		0x09
+#define CMOS_REGISTER_STATUS_1	0x0A
+#define CMOS_REGISTER_STATUS_2	0x0B
+
+namespace RTC
+{
+
+	static bool get_update_in_progress()
+	{
+		IO::outb(CMOS_ADDRESS, CMOS_REGISTER_STATUS_1);
+		return IO::inb(CMOS_DATA) & 0x80;
+	}
+
+	static uint8_t get_rtc_register(uint8_t reg)
+	{
+		IO::outb(CMOS_ADDRESS, reg);
+		return IO::inb(CMOS_DATA);
+	}
+
+	static void get_time(Time& out)
+	{
+		out.second	= get_rtc_register(CMOS_REGISTER_SECOND);
+		out.minute	= get_rtc_register(CMOS_REGISTER_MINUTE);
+		out.hour	= get_rtc_register(CMOS_REGISTER_HOUR);
+		out.day		= get_rtc_register(CMOS_REGISTER_DAY);
+		out.month	= get_rtc_register(CMOS_REGISTER_MONTH);
+		out.year	= get_rtc_register(CMOS_REGISTER_YEAR);
+	}
+
+	Time GetCurrentTime()
+	{
+		Time last_time	= {};
+		Time time		= {};
+
+		while (get_update_in_progress())
+			continue;
+
+		get_time(time);
+		last_time.second = time.second + 1;
+
+		while (memcmp(&last_time, &time, sizeof(Time)))
+		{
+			last_time = time;
+			get_time(time);
+		}
+		
+		uint8_t regB = get_rtc_register(0x0B);
+
+		// Convert BCD to binary values if necessary
+		if (!(regB & 0x04))
+		{
+            time.second	=  (time.second	& 0x0F) + ((time.second	/ 16) * 10);
+            time.minute	=  (time.minute	& 0x0F) + ((time.minute	/ 16) * 10);
+            time.hour	= ((time.hour	& 0x0F) + (((time.hour & 0x70) / 16) * 10) ) | (time.hour & 0x80);
+            time.day	=  (time.day	& 0x0F) + ((time.day	/ 16) * 10);
+            time.month	=  (time.month	& 0x0F) + ((time.month	/ 16) * 10);
+            time.year	=  (time.year	& 0x0F) + ((time.year	/ 16) * 10);
+		}
+
+		// Convert 12 hour clock to 24 hour clock if necessary
+		if (!(regB & 0x02) && (time.hour & 0x80))
+			time.hour = ((time.hour & 0x7F) + 12) % 24;
+
+		// Calculate the full 4 digit year
+		time.year += (CURRENT_YEAR / 100) * 100;
+		if (time.year < CURRENT_YEAR)
+			time.year += 100;
+
+		return time;
+	}
+
+}

kernel/kernel/kernel.cpp

@@ -8,6 +8,7 @@
 #include <kernel/panic.h>
 #include <kernel/PIC.h>
 #include <kernel/PIT.h>
+#include <kernel/RTC.h>
 #include <kernel/Serial.h>
 #include <kernel/tty.h>
 
@@ -63,9 +64,10 @@ void kernel_main(multiboot_info_t* mbi, uint32_t magic)
 	PIT::initialize();
 	Keyboard::initialize(on_key_press);
 
-	kprintln("Hello from the kernel!");
+	auto time = RTC::GetCurrentTime();
+	kprintln("Today is {2}:{2}:{2} {2}.{2}.{4}", time.hour, time.minute, time.second, time.day, time.month, time.year);
 
-	kprint("HHHHHHHHHHHHHHHHHHHHHHHHHHHHH\e[20D.\e[3K");
+	kprintln("Hello from the kernel!");
 
 	ENABLE_INTERRUPTS();