[slx-clock] Try to guess RTC mode and write time back if no mode is specified

1 files changed, 24 insertions, 7 deletions

diff --git a/modules.d/slx-clock/hooks/s3-ntp-sync.sh b/modules.d/slx-clock/hooks/s3-ntp-sync.sh
index 7bbcd14a..c4be6161 100755
--- a/modules.d/slx-clock/hooks/s3-ntp-sync.sh
+++ b/modules.d/slx-clock/hooks/s3-ntp-sync.sh
@@ -3,6 +3,28 @@
 
 . /etc/openslx
 
+adjust_rtc() {
+	if [ "$SLX_BIOS_CLOCK" = "local" ]; then
+		usleep 100000
+		hwclock -l -w || echo "... but could not set BIOS clock to localtime"
+	elif [ "$SLX_BIOS_CLOCK" = "utc" ]; then
+		usleep 100000
+		hwclock -u -w || echo "... but could not set BIOS clock to UTC"
+	else
+		local rtc sys diff arg
+		for arg in "-l" "-u"; do
+			rtc=$( date -d "$( LC_ALL=C hwclock "$arg" | sed -r 's/ *[0-9.]+ seconds$//' )" +%s )
+			sys=$( date +%s )
+			diff=$(( sys - rtc ))
+			if [ "$diff" -gt -900 ] && [ "$diff" -lt 900 ]; then
+				# Less than 15 minutes off, assume it's the correct mode
+				hwclock "$arg" -w || echo "... but could not set BIOS clock ($arg)"
+				break
+			fi
+		done
+	fi
+}
+
 # Try to merge with servers from DHCP. Prefer DHCP, skip duplicates
 for SERVER in $SLX_NTP_SERVER; do
 	if ! echo "$SLX_DHCP_NTP" | grep -wq "$SERVER"; then
@@ -13,13 +35,7 @@ SUCCESS=
 for SERVER in $SLX_DHCP_NTP; do
 	if timeout 3 ntpd -q -n -p "$SERVER"; then
 		echo "Successfully queried $SERVER for time."
-		if [ "$SLX_BIOS_CLOCK" = "local" ]; then
-			usleep 100000
-			hwclock -l -w || echo "... but could not set BIOS clock to localtime"
-		elif [ "$SLX_BIOS_CLOCK" = "utc" ]; then
-			usleep 100000
-			hwclock -u -w || echo "... but could not set BIOS clock to UTC"
-		fi
+		adjust_rtc
 		SUCCESS=1
 		break
 	fi
@@ -40,6 +56,7 @@ if [ -z "$SUCCESS" ]; then
 		fi
 		echo "Setting time to SLX_NOW ($SLX_NOW, corrected $TTS)"
 		date -s "@$TTS"
+		adjust_rtc
 	else
 		echo "No fallback option for timesync available, relying on correct RTC setup"
 		if [ "$SLX_BIOS_CLOCK" = "local" ]; then