Working RTC access

arch/i386/cmos.c

@@ -0,0 +1,68 @@
+#include <kernel/cmos.h>
+
+int _check_update_in_progress(void) {
+  unsigned char ret_val = 0;
+  __asm__ volatile("mov $0x0A, %%al\n\t" "outb %%al, $0x70\n\t" "inb $0x71, %%al\n\t" "mov %%al, %0":"=b" (ret_val)::"%al");
+  return ret_val;
+}
+
+unsigned char _get_rtc_reg(unsigned char reg) {
+  unsigned char ret_val = 0;
+  __asm__ volatile("mov %1, %%al\n\t" "outb %%al, $0x70\n\t" "inb $0x71, %%al\n\t" "mov %%al, %0":"=b" (ret_val):"c" (reg):"%al");
+  return ret_val;
+}
+
+unsigned long int read_rtc() {
+  unsigned char regb;
+  unsigned long int ret_val;
+
+  /* I might need to add this check back in, but it's fine for now. */
+  /* while(_check_update_in_progress()); */
+
+  cur_time.second = _get_rtc_reg(0x00);
+  cur_time.minute = _get_rtc_reg(0x02);
+  cur_time.hour = _get_rtc_reg(0x04);
+  cur_time.day = _get_rtc_reg(0x07);
+  cur_time.month = _get_rtc_reg(0x08);
+  cur_time.year = _get_rtc_reg(0x09);
+
+  regb = _get_rtc_reg(0x0B);
+
+  /* Convert bcd to binary if needed */
+  if(!(regb & 0x04)) {
+    cur_time.second = (cur_time.second & 0x0F) + ((cur_time.second / 16) * 10);
+    cur_time.minute = (cur_time.minute & 0x0F) + ((cur_time.minute / 16) * 10);
+    cur_time.hour = ((cur_time.hour & 0x0F) + (((cur_time.hour & 0x70) / 16) * 10)) | (cur_time.hour & 0x80);
+    cur_time.day = (cur_time.day & 0x0F) + ((cur_time.day / 16) * 10);
+    cur_time.month = (cur_time.month & 0x0F) + ((cur_time.month / 16) * 10);
+    cur_time.year = (cur_time.year & 0x0F) + ((cur_time.year / 16) * 10);
+  }
+
+  /* Convert to 24H time if needed */
+  if(!(regb & 0x02) && (cur_time.hour & 0x80)) {
+    cur_time.hour = ((cur_time.hour & 0x7F) + 12) % 24;
+  }
+
+  /* Get year. TODO: Use century register for this. */
+  cur_time.year += (RELEASE_YEAR / 100) * 100; /* Add century of release year */
+  if(cur_time.year < RELEASE_YEAR) cur_time.year += 100;
+
+  ret_val = cur_time.second;
+  ret_val += cur_time.minute * 60;
+  ret_val += cur_time.hour * 3600;
+  unsigned int tot_days = cur_time.day;
+  unsigned char month_days[12] = {31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};
+  for(unsigned int i = 1970; i < cur_time.year; i++) {
+    if(i % 400 == 0 || (i % 100 != 0 && i % 4 == 0)) {
+      tot_days += 366;
+    }
+    else {
+      tot_days += 365;
+    }
+  }
+  for(int i = 0; i < (cur_time.month - 1); i++) {
+    tot_days += month_days[i];
+  }
+  ret_val += tot_days * 86400;
+  return ret_val;
+}

include/kernel/cmos.h

@@ -0,0 +1,27 @@
+#ifndef _KERNEL_CMOS
+#define _KERNEL_CMOS
+
+/* This is kinda important, and has to be changed each year. */
+#define RELEASE_YEAR 2020
+
+struct _rtc_val {
+  unsigned char second;
+  unsigned char minute;
+  unsigned char hour;
+  unsigned char day;
+  unsigned char month;
+  unsigned int year;
+};
+
+static struct _rtc_val cur_time;
+
+enum {
+  cmos_address = 0x70,
+  cmos_data = 0x71
+};
+
+int _check_update_in_progress(void);
+unsigned char _get_rtc_reg(unsigned char reg);
+unsigned long int read_rtc();
+
+#endif