logind: be a bit more rigid with seat names

src/logind-seat.c

@@ -492,5 +492,8 @@ bool seat_name_is_valid(const char *name) {
                 if (!seat_name_valid_char(*p))
                         return false;
 
+        if (strlen(name) > 255)
+                return false;
+
         return true;
 }

src/logind.h

@@ -45,6 +45,7 @@
  * use device_has_tag() as soon as it is available
  * trigger based on libudev if available
  * enumerate recursively with libudev when triggering
+ * use sysfs in device hash table, not sysname, when fb driver is fixed
  *
  * non-local X11 server
  * reboot/shutdown halt management