[PATCH 6.1 088/280] testptp: Add option to open PHC in readonly mode

Greg Kroah-Hartman
2026-02-04T15:09:35Z

From: Wojtek Wasko <wwasko@nvidia.com>

[ Upstream commit 76868642e42795353106197abf9c607ad80f4c9e ]

PTP Hardware Clocks no longer require WRITE permission to perform
readonly operations, such as listing device capabilities or listening to
EXTTS events once they have been enabled by a process with WRITE
permissions.

Add '-r' option to testptp to open the PHC in readonly mode instead of
the default read-write mode. Skip enabling EXTTS if readonly mode is
requested.

Acked-by: Richard Cochran <richardcochran@gmail.com>
Reviewed-by: Vadim Fedorenko <vadim.fedorenko@linux.dev>
Signed-off-by: Wojtek Wasko <wwasko@nvidia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
tools/testing/selftests/ptp/testptp.c | 37 +++++++++++++++++----------
1 file changed, 23 insertions(+), 14 deletions(-)

diff --git a/tools/testing/selftests/ptp/testptp.c b/tools/testing/selftests/ptp/testptp.c
index 2323a3329b298..532fb6a5d0591 100644
--- a/tools/testing/selftests/ptp/testptp.c
+++ b/tools/testing/selftests/ptp/testptp.c
@@ -140,6 +140,7 @@ static void usage(char *progname)
" -H val set output phase to 'val' nanoseconds (requires -p)\n"
" -w val set output pulse width to 'val' nanoseconds (requires -p)\n"
" -P val enable or disable (val=1|0) the system clock PPS\n"
+ " -r open the ptp clock in readonly mode\n"
" -s set the ptp clock time from the system time\n"
" -S set the system time from the ptp clock time\n"
" -t val shift the ptp clock time by 'val' seconds\n"
@@ -188,6 +189,7 @@ int main(int argc, char *argv[])
int pin_index = -1, pin_func;
int pps = -1;
int seconds = 0;
+ int readonly = 0;
int settime = 0;
int channel = -1;
clockid_t ext_clockid = CLOCK_REALTIME;
@@ -200,7 +202,7 @@ int main(int argc, char *argv[])

progname = strrchr(argv[0], '/');
progname = progname ? 1+progname : argv[0];
- while (EOF != (c = getopt(argc, argv, "cd:e:f:F:ghH:i:k:lL:n:o:p:P:sSt:T:w:x:Xy:z"))) {
+ while (EOF != (c = getopt(argc, argv, "cd:e:f:F:ghH:i:k:lL:n:o:p:P:rsSt:T:w:x:Xy:z"))) {
switch (c) {
case 'c':
capabilities = 1;
@@ -252,6 +254,9 @@ int main(int argc, char *argv[])
case 'P':
pps = atoi(optarg);
break;
+ case 'r':
+ readonly = 1;
+ break;
case 's':
settime = 1;
break;
@@ -308,7 +313,7 @@ int main(int argc, char *argv[])
}
}

- fd = open(device, O_RDWR);
+ fd = open(device, readonly ? O_RDONLY : O_RDWR);
if (fd < 0) {
fprintf(stderr, "opening %s: %s\n", device, strerror(errno));
return -1;
@@ -434,14 +439,16 @@ int main(int argc, char *argv[])
}

if (extts) {
- memset(&extts_request, 0, sizeof(extts_request));
- extts_request.index = index;
- extts_request.flags = PTP_ENABLE_FEATURE;
- if (ioctl(fd, PTP_EXTTS_REQUEST, &extts_request)) {
- perror("PTP_EXTTS_REQUEST");
- extts = 0;
- } else {
- puts("external time stamp request okay");
+ if (!readonly) {
+ memset(&extts_request, 0, sizeof(extts_request));
+ extts_request.index = index;
+ extts_request.flags = PTP_ENABLE_FEATURE;
+ if (ioctl(fd, PTP_EXTTS_REQUEST, &extts_request)) {
+ perror("PTP_EXTTS_REQUEST");
+ extts = 0;
+ } else {
+ puts("external time stamp request okay");
+ }
}
for (; extts; extts--) {
cnt = read(fd, &event, sizeof(event));
@@ -453,10 +460,12 @@ int main(int argc, char *argv[])
event.t.sec, event.t.nsec);
fflush(stdout);
}
- /* Disable the feature again. */
- extts_request.flags = 0;
- if (ioctl(fd, PTP_EXTTS_REQUEST, &extts_request)) {
- perror("PTP_EXTTS_REQUEST");
+ if (!readonly) {
+ /* Disable the feature again. */
+ extts_request.flags = 0;
+ if (ioctl(fd, PTP_EXTTS_REQUEST, &extts_request)) {
+ perror("PTP_EXTTS_REQUEST");
+ }
}
}

--
2.51.0