ntp: Add ADJ_SETOFFSET mode bit

This patch adds a new mode bit into the timex structure. When set, the bit
instructs the kernel to add the given time value to the current time.
Signed-off-by: NRichard Cochran <richard.cochran@omicron.at>
Acked-by: NJohn Stultz <johnstul@us.ibm.com>
LKML-Reference: <20110201134320.688829863@linutronix.de>
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>

include/linux/timex.h

@@ -73,7 +73,7 @@ struct timex {
 	long tolerance;		/* clock frequency tolerance (ppm)
 				 * (read only)
 				 */
-	struct timeval time;	/* (read only) */
+	struct timeval time;	/* (read only, except for ADJ_SETOFFSET) */
 	long tick;		/* (modified) usecs between clock ticks */
 
 	long ppsfreq;           /* pps frequency (scaled ppm) (ro) */
@@ -102,6 +102,7 @@ struct timex {
 #define ADJ_STATUS		0x0010	/* clock status */
 #define ADJ_TIMECONST		0x0020	/* pll time constant */
 #define ADJ_TAI			0x0080	/* set TAI offset */
+#define ADJ_SETOFFSET		0x0100  /* add 'time' to current time */
 #define ADJ_MICRO		0x1000	/* select microsecond resolution */
 #define ADJ_NANO		0x2000	/* select nanosecond resolution */
 #define ADJ_TICK		0x4000	/* tick value */

kernel/time/ntp.c

@@ -648,6 +648,17 @@ int do_adjtimex(struct timex *txc)
 			hrtimer_cancel(&leap_timer);
 	}
 
+	if (txc->modes & ADJ_SETOFFSET) {
+		struct timespec delta;
+		if ((unsigned long)txc->time.tv_usec >= NSEC_PER_SEC)
+			return -EINVAL;
+		delta.tv_sec  = txc->time.tv_sec;
+		delta.tv_nsec = txc->time.tv_usec;
+		if (!(txc->modes & ADJ_NANO))
+			delta.tv_nsec *= 1000;
+		timekeeping_inject_offset(&delta);
+	}
+
 	getnstimeofday(&ts);
 
 	write_seqlock_irq(&xtime_lock);