[source] ugps: fix and improve init script

[LEDE Commits]

pepe2k pushed a commit to source.git, branch lede-17.01:
https://git.lede-project.org/0cb669b46976a83b94bba26b4a54424e513dafc4

commit 0cb669b46976a83b94bba26b4a54424e513dafc4
Author: Piotr Dymacz <pepe2k at gmail.com>
AuthorDate: Sun Mar 5 19:30:44 2017 +0100

    ugps: fix and improve init script
    
    The ugps tool expects device path in last argument. If it's provided
    before other options, they won't be processed at all.
    
    Additionally, make it possible to use absolute path for gps character
    device in related uci configuration.
    
    Signed-off-by: Piotr Dymacz <pepe2k at gmail.com>
---
 package/utils/ugps/Makefile        | 2 +-
 package/utils/ugps/files/ugps.init | 8 ++++++--
 2 files changed, 7 insertions(+), 3 deletions(-)

diff --git a/package/utils/ugps/Makefile b/package/utils/ugps/Makefile
index 9dc33ca..0243b77 100644
--- a/package/utils/ugps/Makefile
+++ b/package/utils/ugps/Makefile
@@ -8,7 +8,7 @@
 include $(TOPDIR)/rules.mk
 
 PKG_NAME:=ugps
-PKG_RELEASE:=2
+PKG_RELEASE:=3
 
 PKG_SOURCE_URL=$(LEDE_GIT)/project/ugps.git
 PKG_SOURCE_PROTO:=git
diff --git a/package/utils/ugps/files/ugps.init b/package/utils/ugps/files/ugps.init
index a7a88c2..157043c 100644
--- a/package/utils/ugps/files/ugps.init
+++ b/package/utils/ugps/files/ugps.init
@@ -14,11 +14,15 @@ start_service() {
 	local tty="$(uci get gps. at gps[-1].tty)"
 	local atime="$(uci get gps. at gps[-1].adjust_time)"
 
-	[ -d "/sys/class/tty/$tty/" ] || return
+	[ -c "$tty" ] || {
+		tty="/dev/$tty"
+		[ -c "$tty" ] || return
+	}
 
 	procd_open_instance
-	procd_set_param command "$PROG" "/dev/$tty"
+	procd_set_param command "$PROG"
 	[ "$atime" -eq 0 ] || procd_append_param command "-a"
+	procd_append_param command "$tty"
 	procd_set_param respawn
 	procd_close_instance
 }