+/*
+ * Special bin2bcd mapping to deal with bcd storage of year.
+ *
+ * 0-69 -> 0xD0
+ * 70-99 (1970 - 1999) -> 0xD0 - 0xF9 (correctly rolls to 0x00)
+ * 100-199 (2000 - 2099) -> 0x00 - 0x99 (does not roll to 0xA0 :-( )
+ * 200-229 (2100 - 2129) -> 0xA0 - 0xC9 (really for completeness)
+ * 230- -> 0xC9
+ *
+ * Confirmed: the only transition that does not work correctly for this rtc
+ * clock is the transition from 2099 to 2100, it proceeds to 2000. We will
+ * accept this issue since the clock retains and transitions the year correctly
+ * in all other conditions.
+ */
+static unsigned char year_bin2bcd(int val)
+{
+ if (val < 70)
+ return 0xD0;
+ if (val < 100)
+ return bin2bcd(val - 20) | 0x80; /* KISS leverage of bin2bcd */
+ if (val >= 230)
+ return 0xC9;
+ if (val >= 200)
+ return bin2bcd(val - 180) | 0x80;
+ return bin2bcd(val - 100);
+}
+
+static int year_bcd2bin(unsigned char val)
+{
+ if (val >= 0xD0)
+ return bcd2bin(val & 0x7F) + 20;
+ if (val >= 0xA0)
+ return bcd2bin(val & 0x7F) + 180;
+ return bcd2bin(val) + 100;
+}
+