diff --git a/phc2sys.c b/phc2sys.c
index 15f8d75..2cd477a 100644
--- a/phc2sys.c
+++ b/phc2sys.c
@@ -74,7 +74,7 @@ struct clock {
 	LIST_ENTRY(clock) dst_list;
 	clockid_t clkid;
 	int phc_index;
-	int sysoff_supported;
+	int sysoff_method;
 	int is_utc;
 	int dest_only;
 	int state;
@@ -255,9 +255,8 @@ static struct clock *clock_add(struct node *node, char *device)
 		c->servo = servo_add(node, c);
 
 	if (clkid != CLOCK_INVALID && clkid != CLOCK_REALTIME)
-		c->sysoff_supported = (SYSOFF_SUPPORTED ==
-				       sysoff_probe(CLOCKID_TO_FD(clkid),
-						    node->phc_readings));
+		c->sysoff_method = sysoff_probe(CLOCKID_TO_FD(clkid),
+						node->phc_readings);
 
 	LIST_INSERT_HEAD(&node->clocks, c, list);
 	return c;
@@ -784,11 +783,12 @@ static int do_loop(struct node *node, int subscriptions)
 				continue;
 
 			if (clock->clkid == CLOCK_REALTIME &&
-			    node->master->sysoff_supported) {
+			    node->master->sysoff_method >= 0) {
 				/* use sysoff */
 				if (sysoff_measure(CLOCKID_TO_FD(node->master->clkid),
+						   node->master->sysoff_method,
 						   node->phc_readings,
-						   &offset, &ts, &delay))
+						   &offset, &ts, &delay) < 0)
 					return -1;
 			} else {
 				/* use phc */
diff --git a/phc_ctl.c b/phc_ctl.c
index 4a78a19..b9a9cf4 100644
--- a/phc_ctl.c
+++ b/phc_ctl.c
@@ -367,10 +367,12 @@ static int do_cmp(clockid_t clkid, int cmdc, char *cmdv[])
 	struct timespec ts, rta, rtb;
 	int64_t sys_offset, delay = 0, offset;
 	uint64_t sys_ts;
+	int method;
 
-	if (SYSOFF_SUPPORTED ==
-	    sysoff_measure(CLOCKID_TO_FD(clkid),
-			   9, &sys_offset, &sys_ts, &delay)) {
+	method = sysoff_probe(CLOCKID_TO_FD(clkid), 9);
+
+	if (method >= 0 && sysoff_measure(CLOCKID_TO_FD(clkid), method, 9,
+					  &sys_offset, &sys_ts, &delay) >= 0) {
 		pr_notice( "offset from CLOCK_REALTIME is %"PRId64"ns\n",
 			sys_offset);
 		return 0;
diff --git a/sysoff.c b/sysoff.c
index 407a01c..f709a9b 100644
--- a/sysoff.c
+++ b/sysoff.c
@@ -73,8 +73,8 @@ static int64_t sysoff_estimate(struct ptp_clock_time *pct, int n_samples,
 	return samples[0].offset;
 }
 
-int sysoff_measure(int fd, int n_samples,
-		   int64_t *result, uint64_t *ts, int64_t *delay)
+static int sysoff_basic(int fd, int n_samples,
+			int64_t *result, uint64_t *ts, int64_t *delay)
 {
 	struct ptp_sys_offset pso;
 	memset(&pso, 0, sizeof(pso));
@@ -84,13 +84,24 @@ int sysoff_measure(int fd, int n_samples,
 		return SYSOFF_RUN_TIME_MISSING;
 	}
 	*result = sysoff_estimate(pso.ts, n_samples, ts, delay);
-	return SYSOFF_SUPPORTED;
+	return SYSOFF_BASIC;
+}
+
+int sysoff_measure(int fd, int method, int n_samples,
+		   int64_t *result, uint64_t *ts, int64_t *delay)
+{
+	switch (method) {
+	case SYSOFF_BASIC:
+		return sysoff_basic(fd, n_samples, result, ts, delay);
+	}
+	return SYSOFF_COMPILE_TIME_MISSING;
 }
 
 int sysoff_probe(int fd, int n_samples)
 {
 	int64_t junk, delay;
 	uint64_t ts;
+	int i;
 
 	if (n_samples > PTP_MAX_SAMPLES) {
 		fprintf(stderr, "warning: %d exceeds kernel max readings %d\n",
@@ -99,7 +110,13 @@ int sysoff_probe(int fd, int n_samples)
 		return SYSOFF_RUN_TIME_MISSING;
 	}
 
-	return sysoff_measure(fd, n_samples, &junk, &ts, &delay);
+	for (i = 0; i < SYSOFF_LAST; i++) {
+		if (sysoff_measure(fd, i, n_samples, &junk, &ts, &delay) < 0)
+			continue;
+		return i;
+	}
+
+	return SYSOFF_RUN_TIME_MISSING;
 }
 
 #else /* !PTP_SYS_OFFSET */
diff --git a/sysoff.h b/sysoff.h
index cb70265..02ecdfa 100644
--- a/sysoff.h
+++ b/sysoff.h
@@ -21,13 +21,14 @@
 #include <stdint.h>
 
 enum {
-	SYSOFF_SUPPORTED,
-	SYSOFF_COMPILE_TIME_MISSING,
-	SYSOFF_RUN_TIME_MISSING,
+	SYSOFF_COMPILE_TIME_MISSING = -2,
+	SYSOFF_RUN_TIME_MISSING = -1,
+	SYSOFF_BASIC,
+	SYSOFF_LAST,
 };
 
 /**
- * Check to see if the PTP_SYS_OFFSET ioctl is supported.
+ * Check to see if a PTP_SYS_OFFSET ioctl is supported.
  * @param fd  An open file descriptor to a PHC device.
  * @return  One of the SYSOFF_ enumeration values.
  */
@@ -36,11 +37,12 @@ int sysoff_probe(int fd, int n_samples);
 /**
  * Measure the offset between a PHC and the system time.
  * @param fd         An open file descriptor to a PHC device.
+ * @param method     A non-negative SYSOFF_ value returned by sysoff_probe().
  * @param n_samples  The number of consecutive readings to make.
  * @param result     The estimated offset in nanoseconds.
  * @param ts         The system time corresponding to the 'result'.
  * @param delay      The delay in reading of the clock in nanoseconds.
  * @return  One of the SYSOFF_ enumeration values.
  */
-int sysoff_measure(int fd, int n_samples,
+int sysoff_measure(int fd, int method, int n_samples,
 		   int64_t *result, uint64_t *ts, int64_t *delay);