1 files changed, 138 insertions, 0 deletions
diff --git a/kernel/src/drivers/cmos.c b/kernel/src/drivers/cmos.c
new file mode 100644
index 0000000..5ac12c3
--- /dev/null
+++ b/kernel/src/drivers/cmos.c
@@ -0,0 +1,138 @@
+#include "print.h"
+#include <stdint.h>
+#include <sys.h>
+#include <time.h>
+
+#define CMOS_WRITE_PORT 0x70
+#define CMOS_READ_PORT  0x71
+
+#define CMOS_REG_SEC    0x00
+#define CMOS_REG_MIN    0x02
+#define CMOS_REG_HOUR   0x04
+#define CMOS_REG_WDAY   0x06
+#define CMOS_REG_MDAY   0x07
+#define CMOS_REG_MON    0x08
+#define CMOS_REG_YEAR   0x09
+#define CMOS_REG_CEN    0x32
+
+static struct Time time;
+static struct Time localtime;
+static int cur_offset = 0;
+
+static uint8_t cmos_read(uint8_t reg) {
+    uint8_t hex, ret;
+    
+    outb(CMOS_WRITE_PORT, reg);
+    hex = inb(CMOS_READ_PORT);
+
+    ret = hex & 0x0F;
+    ret += (hex & 0xF0) / 16 * 10;
+
+    return ret;
+}
+
+static int mday_offset[12] = {
+    0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334
+};
+
+static int month_days[12] = {
+    31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31
+};
+
+static void update_localtime(void) {
+
+    int change, max;
+
+    // set localtime
+    localtime = time;
+
+    // do we acutally need to do anything
+    if (cur_offset == 0) return;
+    localtime.hour += cur_offset;
+    
+    // check if day rolled over
+    change = localtime.hour < 0 ? -1 : localtime.hour >= 24 ? 1 : 0;
+    if (!change) return;
+
+    // roll over day
+    localtime.hour = (localtime.hour + 24) % 24;
+    localtime.wday = (localtime.wday + change + 7) % 7;
+    localtime.mday += change;
+    localtime.yday += change;
+    
+    // check if month rolled over
+    max = month_days[localtime.mon];
+    if (localtime.leap && localtime.mon == 1) max++;
+    change = localtime.mday < 0 ? -1 : localtime.mday >= max ? 1 : 0;
+    if (!change) return;
+
+    // roll over month
+    localtime.mon = (localtime.mon + change + 12) % 12;
+    
+    // check if year rolled over
+    max = localtime.leap ? 366 : 365;
+    change = localtime.yday < 0 ? -1 : localtime.yday >= max ? 1 : 0;
+    if (!change) return;
+
+    // roll over year
+    localtime.yn += change;
+
+    // check if cen rolled over
+    change = localtime.yn < 0 ? -1 : localtime.yn >= 100 ? 1 : 0;
+    if (!change) goto year;
+
+    // roll over cen
+    localtime.cen += change;
+
+
+year:
+
+    localtime.year = localtime.yn + localtime.cen * 100;
+    localtime.leap = localtime.year % 4 == 0 && localtime.year % 100 != 0;
+
+    if (localtime.leap && localtime.yday == -1)
+        localtime.yday = 365;
+    else if (localtime.yday == -1)
+        localtime.yday = 364;
+    else
+        localtime.yday = 0;
+
+    localtime.year -= 1900;
+
+}
+
+void rtc_set_timezone(int offset) {
+    cur_offset = offset;
+}
+
+void rtc_update(void) {
+    time.sec = cmos_read(CMOS_REG_SEC);
+    time.min = cmos_read(CMOS_REG_MIN);
+    time.hour = cmos_read(CMOS_REG_HOUR);
+    time.wday = cmos_read(CMOS_REG_WDAY) - 1;
+    time.mday = cmos_read(CMOS_REG_MDAY);
+    time.mon = cmos_read(CMOS_REG_MON) - 1;
+    time.yn = cmos_read(CMOS_REG_YEAR);
+    time.cen = 20;
+
+    time.year = time.yn + time.cen * 100;
+
+    time.leap = time.year % 4 == 0 && time.year % 100 != 0;
+
+    time.yday = mday_offset[time.mon] + time.mday;
+
+    if (time.leap && time.mon > 2)
+        time.yday++;
+    
+    time.year -= 1900;
+
+    update_localtime();
+}
+
+struct Time *rtc_utctime(void) {
+    return &time;
+}
+
+struct Time *rtc_localtime(void) {
+     return &localtime;
+}