[PATCH] ptp: measure the time offset between PHC and system clock

STALE4696d

8 messages, 4 authors, 2013-09-23 · open the first message on its own page

[PATCH] ptp: measure the time offset between PHC and system clock

From: Dong Zhu <hidden>
Date: 2013-09-14 08:04:55

This patch add a method into testptp.c to measure the time offset
between phc and system clock through the ioctl PTP_SYS_OFFSET.

Signed-off-by: Dong Zhu <redacted>
---
 Documentation/ptp/testptp.c | 40 ++++++++++++++++++++++++++++++++++++++--
 1 file changed, 38 insertions(+), 2 deletions(-)

diff --git a/Documentation/ptp/testptp.c b/Documentation/ptp/testptp.c
index f59ded0..72bb030 100644
--- a/Documentation/ptp/testptp.c
+++ b/Documentation/ptp/testptp.c

@@ -112,6 +112,7 @@ static void usage(char *progname)
 		" -f val     adjust the ptp clock frequency by 'val' ppb\n"
 		" -g         get the ptp clock time\n"
 		" -h         prints this message\n"
+		" -k val     measure the time offset between PHC and system clock\n"
 		" -p val     enable output with a period of 'val' nanoseconds\n"
 		" -P val     enable or disable (val=1|0) the system clock PPS\n"
 		" -s         set the ptp clock time from the system time\n"

@@ -133,8 +134,12 @@ int main(int argc, char *argv[])
 	struct itimerspec timeout;
 	struct sigevent sigevent;
 
+	struct ptp_clock_time *pct;
+	struct ptp_sys_offset *sysoff;
+
+
 	char *progname;
-	int c, cnt, fd;
+	int i, c, cnt, fd;
 
 	char *device = DEVICE;
 	clockid_t clkid;

@@ -144,6 +149,8 @@ int main(int argc, char *argv[])
 	int extts = 0;
 	int gettime = 0;
 	int oneshot = 0;
+	int offset = 0;
+	int n_samples = 0;
 	int periodic = 0;
 	int perout = -1;
 	int pps = -1;

@@ -151,7 +158,7 @@ int main(int argc, char *argv[])
 
 	progname = strrchr(argv[0], '/');
 	progname = progname ? 1+progname : argv[0];
-	while (EOF != (c = getopt(argc, argv, "a:A:cd:e:f:ghp:P:sSt:v"))) {
+	while (EOF != (c = getopt(argc, argv, "a:A:cd:e:f:ghk:p:P:sSt:v"))) {
 		switch (c) {
 		case 'a':
 			oneshot = atoi(optarg);

@@ -174,6 +181,10 @@ int main(int argc, char *argv[])
 		case 'g':
 			gettime = 1;
 			break;
+		case 'k':
+			offset = 1;
+			n_samples = atoi(optarg);
+			break;
 		case 'p':
 			perout = atoi(optarg);
 			break;

@@ -376,6 +387,31 @@ int main(int argc, char *argv[])
 		}
 	}
 
+	if (offset) {
+		sysoff = calloc(1, sizeof(*sysoff));
+		if (!sysoff) {
+			perror("calloc");
+			return -1;
+		}
+		sysoff->n_samples = n_samples;
+
+		if (ioctl(fd, PTP_SYS_OFFSET, sysoff))
+			perror("PTP_SYS_OFFSET");
+		else
+			puts("time offset between PHC and
+					 system clock request okay");
+
+		pct = &sysoff->ts[0];
+		for (i = 0; i < sysoff->n_samples; i++, pct++) {
+			printf("system time: %ld.%ld\n", pct->sec, pct->nsec);
+			pct++;
+			printf("phc    time: %ld.%ld\n\n", pct->sec, pct->nsec);
+		}
+		printf("system time: %ld.%ld\n", pct->sec, pct->nsec);
+
+		free(sysoff);
+	}
+
 	close(fd);
 	return 0;
 }

-- 
1.7.11.7


-- 
Best Regards,
Dong Zhu

Re: [PATCH] ptp: measure the time offset between PHC and system clock

From: Richard Cochran <richardcochran@gmail.com>
Date: 2013-09-14 14:32:10

On Sat, Sep 14, 2013 at 04:03:06PM +0800, Dong Zhu wrote:

This patch add a method into testptp.c to measure the time offset
between phc and system clock through the ioctl PTP_SYS_OFFSET.

This is a nice addition to the testptp program. I do have a few
comments, below.

First off, the subject line should mention testptp. How about this?

    [PATCH] ptp: add the PTP_SYS_OFFSET ioctl to the testptp program

quoted hunk

Signed-off-by: Dong Zhu <redacted>
---
 Documentation/ptp/testptp.c | 40 ++++++++++++++++++++++++++++++++++++++--
 1 file changed, 38 insertions(+), 2 deletions(-)

diff --git a/Documentation/ptp/testptp.c b/Documentation/ptp/testptp.c
index f59ded0..72bb030 100644
--- a/Documentation/ptp/testptp.c
+++ b/Documentation/ptp/testptp.c

@@ -112,6 +112,7 @@ static void usage(char *progname)
 		" -f val     adjust the ptp clock frequency by 'val' ppb\n"
 		" -g         get the ptp clock time\n"
 		" -h         prints this message\n"
+		" -k val     measure the time offset between PHC and system clock\n"

The help message should tell the user what 'val' is.

quoted hunk

 		" -p val     enable output with a period of 'val' nanoseconds\n"
 		" -P val     enable or disable (val=1|0) the system clock PPS\n"
 		" -s         set the ptp clock time from the system time\n"

@@ -133,8 +134,12 @@ int main(int argc, char *argv[])
 	struct itimerspec timeout;
 	struct sigevent sigevent;
 
+	struct ptp_clock_time *pct;
+	struct ptp_sys_offset *sysoff;
+
+
 	char *progname;
-	int c, cnt, fd;
+	int i, c, cnt, fd;
 
 	char *device = DEVICE;
 	clockid_t clkid;
@@ -144,6 +149,8 @@ int main(int argc, char *argv[])
 	int extts = 0;
 	int gettime = 0;
 	int oneshot = 0;
+	int offset = 0;
+	int n_samples = 0;
 	int periodic = 0;
 	int perout = -1;
 	int pps = -1;
@@ -151,7 +158,7 @@ int main(int argc, char *argv[])
 
 	progname = strrchr(argv[0], '/');
 	progname = progname ? 1+progname : argv[0];
-	while (EOF != (c = getopt(argc, argv, "a:A:cd:e:f:ghp:P:sSt:v"))) {
+	while (EOF != (c = getopt(argc, argv, "a:A:cd:e:f:ghk:p:P:sSt:v"))) {
 		switch (c) {
 		case 'a':
 			oneshot = atoi(optarg);
@@ -174,6 +181,10 @@ int main(int argc, char *argv[])
 		case 'g':
 			gettime = 1;
 			break;
+		case 'k':
+			offset = 1;
+			n_samples = atoi(optarg);
+			break;
 		case 'p':
 			perout = atoi(optarg);
 			break;
@@ -376,6 +387,31 @@ int main(int argc, char *argv[])
 		}
 	}
 
+	if (offset) {
+		sysoff = calloc(1, sizeof(*sysoff));
+		if (!sysoff) {
+			perror("calloc");
+			return -1;
+		}
+		sysoff->n_samples = n_samples;
+
+		if (ioctl(fd, PTP_SYS_OFFSET, sysoff))
+			perror("PTP_SYS_OFFSET");
+		else
+			puts("time offset between PHC and
+					 system clock request okay");
+
+		pct = &sysoff->ts[0];
+		for (i = 0; i < sysoff->n_samples; i++, pct++) {
+			printf("system time: %ld.%ld\n", pct->sec, pct->nsec);
+			pct++;
+			printf("phc    time: %ld.%ld\n\n", pct->sec, pct->nsec);

                                                    ^^^^
I think the output would look nicer with only one newline. After all,
each measurement is a {sys,phc,sys} triplet and not a {sys,phc} pair.

+		}
+		printf("system time: %ld.%ld\n", pct->sec, pct->nsec);
+
+		free(sysoff);
+	}
+

Thanks,
Richard

Re: [PATCH] ptp: add the PTP_SYS_OFFSET ioctl to the testptp program clock

From: Dong Zhu <hidden>
Date: 2013-09-14 15:41:37

On Sat, Sep 14, 2013 at 04:31:46PM +0200, Richard Cochran wrote:

On Sat, Sep 14, 2013 at 04:03:06PM +0800, Dong Zhu wrote:

quoted

This patch add a method into testptp.c to measure the time offset
between phc and system clock through the ioctl PTP_SYS_OFFSET.

This is a nice addition to the testptp program. I do have a few
comments, below.

Thanks very much for your comments, I have modified the patch as below,
Cuold you have a look at it again ? Any comments would be appreciated.

From 655b45785a85599d5fff5eb3b8d9b49b72f2991f Mon Sep 17 00:00:00 2001

From: Dong Zhu <redacted> 
Date: Sat, 14 Sep 2013 23:32:14 +0800

This patch add a method into testptp.c to measure the time offset
between phc and system clock through the ioctl PTP_SYS_OFFSET.

Signed-off-by: Dong Zhu <redacted>
---
 Documentation/ptp/testptp.c | 40 ++++++++++++++++++++++++++++++++++++++--
 1 file changed, 38 insertions(+), 2 deletions(-)

diff --git a/Documentation/ptp/testptp.c b/Documentation/ptp/testptp.c
index f59ded0..8acdc70 100644
--- a/Documentation/ptp/testptp.c
+++ b/Documentation/ptp/testptp.c

@@ -112,6 +112,8 @@ static void usage(char *progname)
 		" -f val     adjust the ptp clock frequency by 'val' ppb\n"
 		" -g         get the ptp clock time\n"
 		" -h         prints this message\n"
+		" -k val     measure the time offset between phc and system clock "
+		"for 'val' times (Maximum 25)\n"
 		" -p val     enable output with a period of 'val' nanoseconds\n"
 		" -P val     enable or disable (val=1|0) the system clock PPS\n"
 		" -s         set the ptp clock time from the system time\n"

@@ -133,8 +135,12 @@ int main(int argc, char *argv[])
 	struct itimerspec timeout;
 	struct sigevent sigevent;
 
+	struct ptp_clock_time *pct;
+	struct ptp_sys_offset *sysoff;
+
+
 	char *progname;
-	int c, cnt, fd;
+	int i, c, cnt, fd;
 
 	char *device = DEVICE;
 	clockid_t clkid;

@@ -144,6 +150,8 @@ int main(int argc, char *argv[])
 	int extts = 0;
 	int gettime = 0;
 	int oneshot = 0;
+	int offset = 0;
+	int n_samples = 0;
 	int periodic = 0;
 	int perout = -1;
 	int pps = -1;

@@ -151,7 +159,7 @@ int main(int argc, char *argv[])
 
 	progname = strrchr(argv[0], '/');
 	progname = progname ? 1+progname : argv[0];
-	while (EOF != (c = getopt(argc, argv, "a:A:cd:e:f:ghp:P:sSt:v"))) {
+	while (EOF != (c = getopt(argc, argv, "a:A:cd:e:f:ghk:p:P:sSt:v"))) {
 		switch (c) {
 		case 'a':
 			oneshot = atoi(optarg);

@@ -174,6 +182,10 @@ int main(int argc, char *argv[])
 		case 'g':
 			gettime = 1;
 			break;
+		case 'k':
+			offset = 1;
+			n_samples = atoi(optarg);
+			break;
 		case 'p':
 			perout = atoi(optarg);
 			break;

@@ -376,6 +388,30 @@ int main(int argc, char *argv[])
 		}
 	}
 
+	if (offset) {
+		sysoff = calloc(1, sizeof(*sysoff));
+		if (!sysoff) {
+			perror("calloc");
+			return -1;
+		}
+		sysoff->n_samples = n_samples;
+
+		if (ioctl(fd, PTP_SYS_OFFSET, sysoff))
+			perror("PTP_SYS_OFFSET");
+		else
+			puts("phc and system clock time offset request okay");
+
+		pct = &sysoff->ts[0];
+		for (i = 0; i < sysoff->n_samples; i++, pct++) {
+			printf("system time: %ld.%ld\n", pct->sec, pct->nsec);
+			pct++;
+			printf("phc    time: %ld.%ld\n", pct->sec, pct->nsec);
+		}
+		printf("system time: %ld.%ld\n", pct->sec, pct->nsec);
+
+		free(sysoff);
+	}
+
 	close(fd);
 	return 0;
 }

-- 
1.7.11.7

-- 
Best Regards,
Dong Zhu

Re: [PATCH] ptp: add the PTP_SYS_OFFSET ioctl to the testptp program clock

From: Richard Cochran <richardcochran@gmail.com>
Date: 2013-09-15 08:48:29

On Sat, Sep 14, 2013 at 11:39:52PM +0800, Dong Zhu wrote:

On Sat, Sep 14, 2013 at 04:31:46PM +0200, Richard Cochran wrote:

quoted

On Sat, Sep 14, 2013 at 04:03:06PM +0800, Dong Zhu wrote:

quoted

This patch add a method into testptp.c to measure the time offset
between phc and system clock through the ioctl PTP_SYS_OFFSET.

This is a nice addition to the testptp program. I do have a few
comments, below.

Thanks very much for your comments, I have modified the patch as below,
Cuold you have a look at it again ? Any comments would be appreciated.

It looks better, but could you please tweak a few more things?

Subject: Re: [PATCH] ptp: add the PTP_SYS_OFFSET ioctl to the testptp program clock

The subject line has the word "clock" at the end by mistake.
 
...

quoted hunk

diff --git a/Documentation/ptp/testptp.c b/Documentation/ptp/testptp.c
index f59ded0..8acdc70 100644
--- a/Documentation/ptp/testptp.c
+++ b/Documentation/ptp/testptp.c

@@ -112,6 +112,8 @@ static void usage(char *progname)
 		" -f val     adjust the ptp clock frequency by 'val' ppb\n"
 		" -g         get the ptp clock time\n"
 		" -h         prints this message\n"
+		" -k val     measure the time offset between phc and system clock "
+		"for 'val' times (Maximum 25)\n"

This line is getting a bit too long for the terminal. Please line up
the text, like this:

		" -k val     measure the time offset between phc and system clock\n"
		"            for 'val' times (Maximum 25)\n"

Also, when you resubmit the patch, add "net-next" and a patch version,
like this: [PATCH net-next v3].

Thanks,
Richard

Re: [PATCH net-next v3] ptp: add the PTP_SYS_OFFSET ioctl to the testptp program

From: Dong Zhu <hidden>
Date: 2013-09-15 09:26:57

Hi Richard, 

Thanks for your comments, I modified the patch and resubmit it again:

From 7636f69b74c34eca14c85fd2d518da6044b94f53 Mon Sep 17 00:00:00 2001

From: Dong Zhu <redacted> 
Date: Sun, 15 Sep 2013 17:12:52 +0800

This patch add a method into testptp.c to measure the time offset
between phc and system clock through the ioctl PTP_SYS_OFFSET.

Signed-off-by: Dong Zhu <redacted>
---
 Documentation/ptp/testptp.c | 40 ++++++++++++++++++++++++++++++++++++++--
 1 file changed, 38 insertions(+), 2 deletions(-)

diff --git a/Documentation/ptp/testptp.c b/Documentation/ptp/testptp.c
index f59ded0..b6f6f47 100644
--- a/Documentation/ptp/testptp.c
+++ b/Documentation/ptp/testptp.c

@@ -112,6 +112,8 @@ static void usage(char *progname)
 		" -f val     adjust the ptp clock frequency by 'val' ppb\n"
 		" -g         get the ptp clock time\n"
 		" -h         prints this message\n"
+		" -k val     measure the time offset between phc and system clock\n"
+		"            for 'val' times (Maximum 25)\n"
 		" -p val     enable output with a period of 'val' nanoseconds\n"
 		" -P val     enable or disable (val=1|0) the system clock PPS\n"
 		" -s         set the ptp clock time from the system time\n"

@@ -133,8 +135,12 @@ int main(int argc, char *argv[])
 	struct itimerspec timeout;
 	struct sigevent sigevent;
 
+	struct ptp_clock_time *pct;
+	struct ptp_sys_offset *sysoff;
+
+
 	char *progname;
-	int c, cnt, fd;
+	int i, c, cnt, fd;
 
 	char *device = DEVICE;
 	clockid_t clkid;

@@ -144,6 +150,8 @@ int main(int argc, char *argv[])
 	int extts = 0;
 	int gettime = 0;
 	int oneshot = 0;
+	int offset = 0;
+	int n_samples = 0;
 	int periodic = 0;
 	int perout = -1;
 	int pps = -1;

@@ -151,7 +159,7 @@ int main(int argc, char *argv[])
 
 	progname = strrchr(argv[0], '/');
 	progname = progname ? 1+progname : argv[0];
-	while (EOF != (c = getopt(argc, argv, "a:A:cd:e:f:ghp:P:sSt:v"))) {
+	while (EOF != (c = getopt(argc, argv, "a:A:cd:e:f:ghk:p:P:sSt:v"))) {
 		switch (c) {
 		case 'a':
 			oneshot = atoi(optarg);

@@ -174,6 +182,10 @@ int main(int argc, char *argv[])
 		case 'g':
 			gettime = 1;
 			break;
+		case 'k':
+			offset = 1;
+			n_samples = atoi(optarg);
+			break;
 		case 'p':
 			perout = atoi(optarg);
 			break;

@@ -376,6 +388,30 @@ int main(int argc, char *argv[])
 		}
 	}
 
+	if (offset) {
+		sysoff = calloc(1, sizeof(*sysoff));
+		if (!sysoff) {
+			perror("calloc");
+			return -1;
+		}
+		sysoff->n_samples = n_samples;
+
+		if (ioctl(fd, PTP_SYS_OFFSET, sysoff))
+			perror("PTP_SYS_OFFSET");
+		else
+			puts("phc and system clock time offset request okay");
+
+		pct = &sysoff->ts[0];
+		for (i = 0; i < sysoff->n_samples; i++, pct++) {
+			printf("system time: %ld.%ld\n", pct->sec, pct->nsec);
+			pct++;
+			printf("phc    time: %ld.%ld\n", pct->sec, pct->nsec);
+		}
+		printf("system time: %ld.%ld\n", pct->sec, pct->nsec);
+
+		free(sysoff);
+	}
+
 	close(fd);
 	return 0;
 }

-- 
1.7.11.7


-- 
Best Regards,
Dong Zhu

Re: [PATCH net-next v4] ptp: add the PTP_SYS_OFFSET ioctl to the testptp program

From: Dong Zhu <hidden>
Date: 2013-09-17 07:34:23

Hi Richard,

I developed a new patch and added a method to estimate the time offset
between system and phc clock.

Could you help reviewing it again ? If it do make sense I hope it could
be accepted.

Thanks !

From e524e3b68f3df3cd91acd814490d092bad05386b Mon Sep 17 00:00:00 2001

This patch add a method into testptp.c to measure the time offset
between phc and system clock through the ioctl PTP_SYS_OFFSET.

Signed-off-by: Dong Zhu <redacted>
---
 Documentation/ptp/testptp.c | 65 +++++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 63 insertions(+), 2 deletions(-)

diff --git a/Documentation/ptp/testptp.c b/Documentation/ptp/testptp.c
index f59ded0..a74d0a8 100644
--- a/Documentation/ptp/testptp.c
+++ b/Documentation/ptp/testptp.c

@@ -100,6 +100,11 @@ static long ppb_to_scaled_ppm(int ppb)
 	return (long) (ppb * 65.536);
 }
 
+static int64_t pctns(struct ptp_clock_time *t)
+{
+	return t->sec * 1000000000LL + t->nsec;
+}
+
 static void usage(char *progname)
 {
 	fprintf(stderr,

@@ -112,6 +117,8 @@ static void usage(char *progname)
 		" -f val     adjust the ptp clock frequency by 'val' ppb\n"
 		" -g         get the ptp clock time\n"
 		" -h         prints this message\n"
+		" -k val     measure the time offset between system and phc clock\n"
+		"            for 'val' times (Maximum 25)\n"
 		" -p val     enable output with a period of 'val' nanoseconds\n"
 		" -P val     enable or disable (val=1|0) the system clock PPS\n"
 		" -s         set the ptp clock time from the system time\n"

@@ -133,8 +140,12 @@ int main(int argc, char *argv[])
 	struct itimerspec timeout;
 	struct sigevent sigevent;
 
+	struct ptp_clock_time *pct;
+	struct ptp_sys_offset *sysoff;
+
+
 	char *progname;
-	int c, cnt, fd;
+	int i, c, cnt, fd;
 
 	char *device = DEVICE;
 	clockid_t clkid;

@@ -144,14 +155,19 @@ int main(int argc, char *argv[])
 	int extts = 0;
 	int gettime = 0;
 	int oneshot = 0;
+	int pct_offset = 0;
+	int n_samples = 0;
 	int periodic = 0;
 	int perout = -1;
 	int pps = -1;
 	int settime = 0;
 
+	int64_t t1, t2, tp;
+	int64_t interval, offset;
+
 	progname = strrchr(argv[0], '/');
 	progname = progname ? 1+progname : argv[0];
-	while (EOF != (c = getopt(argc, argv, "a:A:cd:e:f:ghp:P:sSt:v"))) {
+	while (EOF != (c = getopt(argc, argv, "a:A:cd:e:f:ghk:p:P:sSt:v"))) {
 		switch (c) {
 		case 'a':
 			oneshot = atoi(optarg);

@@ -174,6 +190,10 @@ int main(int argc, char *argv[])
 		case 'g':
 			gettime = 1;
 			break;
+		case 'k':
+			pct_offset = 1;
+			n_samples = atoi(optarg);
+			break;
 		case 'p':
 			perout = atoi(optarg);
 			break;

@@ -376,6 +396,47 @@ int main(int argc, char *argv[])
 		}
 	}
 
+	if (pct_offset) {
+		if (n_samples <= 0 || n_samples > 25) {
+			puts("n_samples should be between 1 and 25");
+			usage(progname);
+			return -1;
+		}
+
+		sysoff = calloc(1, sizeof(*sysoff));
+		if (!sysoff) {
+			perror("calloc");
+			return -1;
+		}
+		sysoff->n_samples = n_samples;
+
+		if (ioctl(fd, PTP_SYS_OFFSET, sysoff))
+			perror("PTP_SYS_OFFSET");
+		else
+			puts("system and phc clock time offset request okay");
+
+		pct = &sysoff->ts[0];
+		for (i = 0; i < sysoff->n_samples; i++) {
+			t1 = pctns(pct+2*i);
+			tp = pctns(pct+2*i+1);
+			t2 = pctns(pct+2*i+2);
+			interval = t2 - t1;
+			offset = (t2 + t1) / 2 - tp;
+
+			printf("system time: %ld.%ld\n",
+				(pct+2*i)->sec, (pct+2*i)->nsec);
+			printf("phc    time: %ld.%ld\n",
+				(pct+2*i+1)->sec, (pct+2*i+1)->nsec);
+			printf("system time: %ld.%ld\n",
+				(pct+2*i+2)->sec, (pct+2*i+2)->nsec);
+			printf("system/phc clock time offset is %ld ns\n"
+				"system     clock time delay  is %ld ns\n",
+				offset, interval);
+		}
+
+		free(sysoff);
+	}
+
 	close(fd);
 	return 0;
 }

-- 
1.7.11.7


-- 
Best Regards,
Dong Zhu

Re: [PATCH net-next v4] ptp: add the PTP_SYS_OFFSET ioctl to the testptp program

From: David Miller <davem@davemloft.net>
Date: 2013-09-23 20:46:44

From: Dong Zhu <redacted>
Date: Tue, 17 Sep 2013 15:32:35 +0800

This patch add a method into testptp.c to measure the time offset
between phc and system clock through the ioctl PTP_SYS_OFFSET.

Signed-off-by: Dong Zhu <redacted>

Applied.

Re: [PATCH] ptp: measure the time offset between PHC and system clock

From: Sergei Shtylyov <hidden>
Date: 2013-09-14 19:21:47

Hello.

On 09/14/2013 12:03 PM, Dong Zhu wrote:

This patch add a method into testptp.c to measure the time offset
between phc and system clock through the ioctl PTP_SYS_OFFSET.

Signed-off-by: Dong Zhu <redacted>
---
  Documentation/ptp/testptp.c | 40 ++++++++++++++++++++++++++++++++++++++--
  1 file changed, 38 insertions(+), 2 deletions(-)

quoted hunk

diff --git a/Documentation/ptp/testptp.c b/Documentation/ptp/testptp.c
index f59ded0..72bb030 100644
--- a/Documentation/ptp/testptp.c
+++ b/Documentation/ptp/testptp.c

[...]

quoted hunk

@@ -376,6 +387,31 @@ int main(int argc, char *argv[])
  		}
  	}

+	if (offset) {
+		sysoff = calloc(1, sizeof(*sysoff));
+		if (!sysoff) {
+			perror("calloc");
+			return -1;
+		}
+		sysoff->n_samples = n_samples;
+
+		if (ioctl(fd, PTP_SYS_OFFSET, sysoff))
+			perror("PTP_SYS_OFFSET");
+		else
+			puts("time offset between PHC and
+					 system clock request okay");

    Don't break the string constant that way, there'll be all spaces between 
"and" and "system" included in it. Do it like this:

			puts("time offset between PHC and "
			     "system clock request okay");

WBR, Sergei

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