Introduce a boot environment variable (clock_compat_osf1) which can

be set to 1 to make FreeBSD and Tru64 coexist peacefully on a dual
boot system and not clobber each other's year in the TOY clock.
(Tru64 uses an offset 52 years higher than one would expect)

Obtained from: NetBSD
MFC After: 1 week

2 files changed, 28 insertions, 13 deletions

diff --git a/sys/alpha/alpha/clock.c b/sys/alpha/alpha/clock.c
index 6cba099..3bc0ce0 100644
--- a/sys/alpha/alpha/clock.c
+++ b/sys/alpha/alpha/clock.c
@@ -71,6 +71,17 @@
 #define	SECYR	((unsigned)(365*SECDAY))	/* seconds per common year */
 
 /*
+ * According to OSF/1's /usr/sys/include/arch/alpha/clock.h,
+ * the console adjusts the RTC years 13..19 to 93..99 and
+ * 20..40 to 00..20. (historical reasons?)
+ * DEC Unix uses an offset to the year to stay outside
+ * the dangerous area for the next couple of years.
+ */
+#define UNIX_YEAR_OFFSET 52 /* 41=>1993, 12=>2064 */
+
+static int clock_year_offset = 0;
+
+/*
  * 32-bit time_t's can't reach leap years before 1904 or after 2036, so we
  * can use a simple formula for leap years.
  */
@@ -472,7 +483,7 @@ inittodr(base)
 	register int days, yr;
 	struct clocktime ct;
 	time_t deltat;
-	int badbase;
+	int badbase, clock_compat_osf1;
 	int s;
 	struct timespec ts;
 
@@ -484,9 +495,22 @@ inittodr(base)
 	} else
 		badbase = 0;
 
+	if (getenv_int("clock_compat_osf1", &clock_compat_osf1)) {
+		if (clock_compat_osf1)
+			clock_year_offset = UNIX_YEAR_OFFSET;
+	}
+
 	CLOCK_GET(clockdev, base, &ct);
 	clockinitted = 1;
 
+#ifdef DEBUG
+	printf("readclock: %d/%d/%d/%d/%d/%d\n", ct.year, ct.mon, ct.day,
+		ct.hour, ct.min, ct.sec);
+#endif
+	ct.year += clock_year_offset;
+	if (ct.year < 70)
+		ct.year += 100;
+	
 	/* simple sanity checks */
 	if (ct.year < 70 || ct.mon < 1 || ct.mon > 12 || ct.day < 1 ||
 	    ct.day > 31 || ct.hour > 23 || ct.min > 59 || ct.sec > 59) {
@@ -595,6 +619,7 @@ resettodr()
 	ct.min = t / SECMIN;
 	ct.sec = t % SECMIN;
 
+	ct.year = (ct.year - clock_year_offset) % 100;
 	CLOCK_SET(clockdev, &ct);
 }
 
diff --git a/sys/dev/dec/mcclock.c b/sys/dev/dec/mcclock.c
index 9cb3af2..a8a94be 100644
--- a/sys/dev/dec/mcclock.c
+++ b/sys/dev/dec/mcclock.c
@@ -84,13 +84,6 @@ mcclock_get(device_t dev, time_t base, struct clocktime *ct)
 	ct->day = regs[MC_DOM];
 	ct->mon = regs[MC_MONTH];
 	ct->year = regs[MC_YEAR];
-	/*
-	 * This chip is not y2k compliant- If it's less than
-	 * 70, we're clearly past the year 2000.
-	 */
-	if (ct->year < 70) {
-		ct->year += 100;
-	}
 }
 
 /*
@@ -112,11 +105,8 @@ mcclock_set(device_t dev, struct clocktime *ct)
 	regs[MC_DOW] = ct->dow;
 	regs[MC_DOM] = ct->day;
 	regs[MC_MONTH] = ct->mon;
-	/*
-	 * This chip is not y2k compliant- write it with
-	 * no more than two digits.
-	 */
-	regs[MC_YEAR] = ct->year % 100;
+	regs[MC_YEAR] = ct->year;
+
 	s = splclock();
 	MC146818_PUTTOD(dev, &regs);
 	splx(s);