1 files changed, 34 insertions, 0 deletions
diff --git a/src/kernel/cmos.c b/src/kernel/cmos.c
new file mode 100644
index 0000000..39f7c4f
--- /dev/null
+++ b/src/kernel/cmos.c
@@ -0,0 +1,34 @@
+#include "cmos.h"
+#include "util.h"
+
+static inline uint8_t read_cmos(uint8_t reg) {
+  outb(0x0070, reg);
+  return inb(0x0071);
+}
+
+//The idea of reading until you get the same value twice, and checking the status register
+//  is from the OSDev Wiki page at <https://wiki.osdev.org/CMOS#The_Real-Time_Clock>.
+struct rtc_time get_rtc_time() {
+  uint8_t prev_sec = -1;
+  struct rtc_time ret;
+get_sec:
+  while (read_cmos(0x0a) & 0x80)
+    ;//spin while rtc is being updated
+  ret.seconds      = read_cmos(0x00);
+  if (ret.seconds != prev_sec) {
+    prev_sec = ret.seconds;
+    goto get_sec;
+  }
+  ret.minutes      = read_cmos(0x02);
+  ret.hours        = read_cmos(0x04);
+  if (ret.hours & 0x80) {
+    ret.hours -= 0x80 - 12;
+    if (ret.hours == 24)
+      ret.hours = 0;
+  }
+  ret.day_of_week  = read_cmos(0x06);
+  ret.day_of_month = read_cmos(0x07);
+  ret.month        = read_cmos(0x08);
+  ret.year         = read_cmos(0x09);
+  return ret;
+}
+\ No newline at end of file