dectmngr: Determine UART from device tree

Instead of hardcoding it, determine UART device to use for communication
with the DCX81 DECT chip using an alias in the device-tree
/aliases/dcx81-uart.

Also use the existence of the alias as an indicator of whether the
device supports DECT instead of checking for hw.board.hasDect in
board-db.

Signed-off-by: Andreas Gnau <andreas.gnau@iopsys.eu>

dectmngr/files/etc/init.d/dectmngr

@@ -10,6 +10,7 @@ NAME=dectmngr
 PROG=/usr/sbin/dectmngr
 LOG_PATH=/var/log/dectmngr
 DB_PATH=/etc/dect
+DCX81_UART_DT_ALIAS=/proc/device-tree/aliases/dcx81-uart
 
 DECT_GPIO=$(db -q get hw.board.dect_gpio)
 
@@ -24,13 +25,43 @@ stop_and_wait_dectmngr() {
 	done
 }
 
+has_dect() {
+	[ -f "$DCX81_UART_DT_ALIAS" ]
+}
+
+get_dcx81_device() {
+	readonly dcx81_uart_dt_node="/proc/device-tree/$(cat "$DCX81_UART_DT_ALIAS" 2>/dev/null)"
+	[ -e "$dcx81_uart_dt_node" ] || return 1
+	for tty_dt_node in /sys/class/tty/*/device/of_node; do
+		if [ "$tty_dt_node" -ef "$dcx81_uart_dt_node" ]; then
+			readonly uevent_file="${tty_dt_node%%/device/of_node}/uevent"
+			local device_name_line
+			device_name_line="$(grep '^DEVNAME=' "$uevent_file")" || return 1
+			readonly device="/dev/${device_name_line##DEVNAME=}"
+			[ -c "$device" ] || return 1
+			printf "%s" "$device"
+			return 0
+		fi
+	done
+	return 1
+}
+
 start_service() {
 	local opt_ext=
 	local rfpi=
 	local model_id=
 	local rxtun=
 
-	test $(db get hw.board.hasDect) = "0" && return
+	if ! has_dect; then
+		logger -t "$PROG" "Not starting because no DECT hardware is available."
+		return 0
+	fi
+
+	local dcx81_uart_device
+	if ! dcx81_uart_device="$(get_dcx81_device)"; then
+		logger -t "$PROG" -p daemon.error "Could not determine DCX81 UART device. Cannot start $PROG"
+		return 1
+	fi
 
 	[ -n "$DECT_GPIO" ] && echo 1 > /sys/class/gpio/gpio${DECT_GPIO}/value
 
@@ -51,19 +82,22 @@ start_service() {
 	config_get log_dect_cmbs global log_dect_cmbs syslog
 
 	procd_open_instance
+
+	# dectmngr takes expects device without /dev
+	readonly dcx81_uart_device_wo_dev="${dcx81_uart_device##/dev/}"
 	case "$log_dect_cmbs" in
 	none)
 		echo "Starting dectmngr with cmbs logging disabled"
-		procd_set_param command $PROG -comname ttyH0 $opt_ext
+		procd_set_param command "$PROG" -comname "$dcx81_uart_device_wo_dev" $opt_ext
 		rm -f $LOG_PATH/*
 		;;
 	file)
 		echo "Starting dectmngr with cmbs logging enabled to file"
-		procd_set_param command $PROG -comname ttyH0 -log $LOG_PATH/dect-cmbs.log $opt_ext
+		procd_set_param command "$PROG" -comname "$dcx81_uart_device_wo_dev" -log $LOG_PATH/dect-cmbs.log $opt_ext
 		;;
 	*)
 		echo "Starting dectmngr with cmbs logging enabled to syslog"
-		procd_set_param command $PROG -comname ttyH0 -syslog $opt_ext
+		procd_set_param command "$PROG" -comname "$dcx81_uart_device_wo_dev" -syslog $opt_ext
 		rm -f $LOG_PATH/*
 		;;
 	esac
@@ -75,7 +109,7 @@ start_service() {
 }
 
 stop_service() {
-	test $(db get hw.board.hasDect) = "0" && return
+	has_dect || return 0
 
 	[ -n "$DECT_GPIO" ] && echo 0 > /sys/class/gpio/gpio${DECT_GPIO}/value
 	stop_and_wait_dectmngr