Initial commit

src/kernel/rtc.c

@@ -0,0 +1,76 @@
+#include "rtc.h"
+#include "io.h"
+
+#define CMOS_ADDRESS 0x70
+#define CMOS_DATA    0x71
+
+static int updating_rtc() {
+    outb(CMOS_ADDRESS, 0x0A);
+    return (inb(CMOS_DATA) & 0x80);
+}
+
+static uint8_t get_rtc_register(int reg) {
+    outb(CMOS_ADDRESS, reg);
+    return inb(CMOS_DATA);
+}
+
+void rtc_get_datetime(int *year, int *month, int *day, int *hour, int *minute, int *second) {
+    uint8_t century;
+    uint8_t last_second;
+    uint8_t last_minute;
+    uint8_t last_hour;
+    uint8_t last_day;
+    uint8_t last_month;
+    uint8_t last_year;
+    uint8_t last_century;
+    uint8_t registerB;
+
+    while (updating_rtc());
+    *second = get_rtc_register(0x00);
+    *minute = get_rtc_register(0x02);
+    *hour = get_rtc_register(0x04);
+    *day = get_rtc_register(0x07);
+    *month = get_rtc_register(0x08);
+    *year = get_rtc_register(0x09);
+    
+    // Note: Century register is not standard, but often 0x32 if ACPI table says so.
+    // For now, assume 20xx
+    
+    do {
+        last_second = *second;
+        last_minute = *minute;
+        last_hour = *hour;
+        last_day = *day;
+        last_month = *month;
+        last_year = *year;
+
+        while (updating_rtc());
+        *second = get_rtc_register(0x00);
+        *minute = get_rtc_register(0x02);
+        *hour = get_rtc_register(0x04);
+        *day = get_rtc_register(0x07);
+        *month = get_rtc_register(0x08);
+        *year = get_rtc_register(0x09);
+    } while( (last_second != *second) || (last_minute != *minute) || (last_hour != *hour) ||
+             (last_day != *day) || (last_month != *month) || (last_year != *year) );
+
+    registerB = get_rtc_register(0x0B);
+
+    // Convert BCD to binary values if necessary
+    if (!(registerB & 0x04)) {
+        *second = (*second & 0x0F) + ((*second / 16) * 10);
+        *minute = (*minute & 0x0F) + ((*minute / 16) * 10);
+        *hour = ( (*hour & 0x0F) + (((*hour & 0x70) / 16) * 10) ) | (*hour & 0x80);
+        *day = (*day & 0x0F) + ((*day / 16) * 10);
+        *month = (*month & 0x0F) + ((*month / 16) * 10);
+        *year = (*year & 0x0F) + ((*year / 16) * 10);
+    }
+
+    // Convert 12 hour clock to 24 hour clock if necessary
+    if (!(registerB & 0x02) && (*hour & 0x80)) {
+        *hour = ((*hour & 0x7F) + 12) % 24;
+    }
+
+    // Calculate full year
+    *year += 2000;
+}