parse-util: introduce parse_dev() helper

src/basic/parse-util.c

@@ -589,3 +589,18 @@ int parse_ip_port(const char *s, uint16_t *ret) {
 
         return 0;
 }
+
+int parse_dev(const char *s, dev_t *ret) {
+        unsigned x, y;
+        dev_t d;
+
+        if (sscanf(s, "%u:%u", &x, &y) != 2)
+                return -EINVAL;
+
+        d = makedev(x, y);
+        if ((unsigned) major(d) != x || (unsigned) minor(d) != y)
+                return -EINVAL;
+
+        *ret = d;
+        return 0;
+}

src/basic/parse-util.h

@@ -30,6 +30,7 @@
 #define MODE_INVALID ((mode_t) -1)
 
 int parse_boolean(const char *v) _pure_;
+int parse_dev(const char *s, dev_t *ret);
 int parse_pid(const char *s, pid_t* ret_pid);
 int parse_mode(const char *s, mode_t *ret);
 int parse_ifindex(const char *s, int *ret);