The kselftest framework defines KSFT_SKIP=4 as the standard exit code
for skipped tests. However, phc.sh currently uses a mix of 'exit 0' and
'exit 1' to indicate skip conditions, which can confuse test harnesses
and CI systems.

This patch introduces ksft_skip=4 variable and unifies all skip exit
paths to use 'exit $ksft_skip', consistent with other selftests like
net/lib.sh and net/fib_nexthops.sh.

Signed-off-by: Junjie Cao <junjie.cao@intel.com>
---
 tools/testing/selftests/ptp/phc.sh | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/tools/testing/selftests/ptp/phc.sh b/tools/testing/selftests/ptp/phc.sh
index ac6e5a6e1d3a..51aad466d989 100755
--- a/tools/testing/selftests/ptp/phc.sh
+++ b/tools/testing/selftests/ptp/phc.sh
@@ -8,17 +8,20 @@ ALL_TESTS="
 "
 DEV=$1
 
+# Kselftest framework requirement - SKIP code is 4.
+ksft_skip=4
+
 ##############################################################################
 # Sanity checks
 
 if [[ "$(id -u)" -ne 0 ]]; then
 	echo "SKIP: need root privileges"
-	exit 0
+	exit $ksft_skip
 fi
 
 if [[ "$DEV" == "" ]]; then
 	echo "SKIP: PTP device not provided"
-	exit 0
+	exit $ksft_skip
 fi
 
 require_command()
@@ -27,7 +30,7 @@ require_command()
 
 	if [[ ! -x "$(command -v "$cmd")" ]]; then
 		echo "SKIP: $cmd not installed"
-		exit 1
+		exit $ksft_skip
 	fi
 }
 
@@ -37,7 +40,7 @@ phc_sanity()
 
 	if [ $? != 0 ]; then
 		echo "SKIP: unknown clock $DEV: No such device"
-		exit 1
+		exit $ksft_skip
 	fi
 }
 
-- 
2.43.0

Some PTP hardware clock (PHC) devices may return -EOPNOTSUPP for
operations like settime, adjtime, or adjfreq. This commonly occurs
with timestamp-only PHC implementations that don't support full clock
control.

For background, syzbot previously exposed a crash risk when PTP clock
drivers lacked required callbacks[1]. Subsequent work[2] made callback
presence a registration requirement. As a result, some drivers (like
iwlwifi MVM/MLD[3]) now provide stub callbacks that return -EOPNOTSUPP
for unsupported operations.

When phc_ctl encounters such devices, the "Operation not supported"
error should be treated as a skip (device limitation) rather than a
test failure. This patch:
- Adds [SKIP] output handling in log_test()
- Detects "Operation not supported" from phc_ctl and returns ksft_skip
- Returns ksft_skip if all tests are skipped, preventing false-positive
  results when testing timestamp-only PHC implementations

Link: https://lore.kernel.org/netdev/20251028043216.1971292-1-junjie.cao@intel.com/ [1]
Link: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=dfb073d32cac [2]
Link: https://lore.kernel.org/netdev/20251204123204.9316-1-ziyao@disroot.org/ [3]
Signed-off-by: Junjie Cao <junjie.cao@intel.com>
---
 tools/testing/selftests/ptp/phc.sh | 49 ++++++++++++++++++++++--------
 1 file changed, 37 insertions(+), 12 deletions(-)

diff --git a/tools/testing/selftests/ptp/phc.sh b/tools/testing/selftests/ptp/phc.sh
index 51aad466d989..9f61c1579edf 100755
--- a/tools/testing/selftests/ptp/phc.sh
+++ b/tools/testing/selftests/ptp/phc.sh
@@ -52,6 +52,7 @@ phc_sanity
 
 # Exit status to return at the end. Set in case one of the tests fails.
 EXIT_STATUS=0
+PASS_COUNT=0
 # Per-test return value. Clear at the beginning of each test.
 RET=0
 
@@ -68,12 +69,18 @@ log_test()
 {
 	local test_name=$1
 
+	if [[ $RET -eq $ksft_skip ]]; then
+		printf "TEST: %-60s  [SKIP]\n" "$test_name"
+		return 0
+	fi
+
 	if [[ $RET -ne 0 ]]; then
 		EXIT_STATUS=1
 		printf "TEST: %-60s  [FAIL]\n" "$test_name"
 		return 1
 	fi
 
+	((PASS_COUNT++))
 	printf "TEST: %-60s  [ OK ]\n" "$test_name"
 	return 0
 }
@@ -92,34 +99,49 @@ tests_run()
 
 settime_do()
 {
-	local res
+	local res out
 
-	res=$(phc_ctl $DEV set 0 wait 120.5 get 2> /dev/null \
-		| awk '/clock time is/{print $5}' \
-		| awk -F. '{print $1}')
+	out=$(LC_ALL=C phc_ctl $DEV set 0 wait 120.5 get 2>&1)
+	if [[ $? -ne 0 ]]; then
+		if echo "$out" | grep -qi "Operation not supported"; then
+			return $ksft_skip
+		fi
+		return 1
+	fi
+	res=$(echo "$out" | awk '/clock time is/{print $5}' | awk -F. '{print $1}')
 
 	(( res == 120 ))
 }
 
 adjtime_do()
 {
-	local res
+	local res out
 
-	res=$(phc_ctl $DEV set 0 adj 10 get 2> /dev/null \
-		| awk '/clock time is/{print $5}' \
-		| awk -F. '{print $1}')
+	out=$(LC_ALL=C phc_ctl $DEV set 0 adj 10 get 2>&1)
+	if [[ $? -ne 0 ]]; then
+		if echo "$out" | grep -qi "Operation not supported"; then
+			return $ksft_skip
+		fi
+		return 1
+	fi
+	res=$(echo "$out" | awk '/clock time is/{print $5}' | awk -F. '{print $1}')
 
 	(( res == 10 ))
 }
 
 adjfreq_do()
 {
-	local res
+	local res out
 
 	# Set the clock to be 1% faster
-	res=$(phc_ctl $DEV freq 10000000 set 0 wait 100.5 get 2> /dev/null \
-		| awk '/clock time is/{print $5}' \
-		| awk -F. '{print $1}')
+	out=$(LC_ALL=C phc_ctl $DEV freq 10000000 set 0 wait 100.5 get 2>&1)
+	if [[ $? -ne 0 ]]; then
+		if echo "$out" | grep -qi "Operation not supported"; then
+			return $ksft_skip
+		fi
+		return 1
+	fi
+	res=$(echo "$out" | awk '/clock time is/{print $5}' | awk -F. '{print $1}')
 
 	(( res == 101 ))
 }
@@ -166,4 +188,7 @@ trap cleanup EXIT
 
 tests_run
 
+if [[ $EXIT_STATUS -eq 0 && $PASS_COUNT -eq 0 ]]; then
+	exit $ksft_skip
+fi
 exit $EXIT_STATUS
-- 
2.43.0