From b4753f7ec45cf4324f84a00aebc4fdcb1ff5c1cb Mon Sep 17 00:00:00 2001
From: Stéphane Raimbault <stephane.raimbault@gmail.com>
Date: Fri, 10 May 2013 01:10:17 +0200
Subject: [PATCH] Returns -1 on invalid mode in modbus_rtu_set_rts

---
 src/modbus-rtu.c | 3 +++
 1 file changed, 3 insertions(+), 0 deletions(-)

diff --git a/src/modbus-rtu.c b/src/modbus-rtu.c
index 3ac7324..690fb9c 100644
--- a/src/modbus-rtu.c
+++ b/src/modbus-rtu.c
@@ -985,6 +985,9 @@ int modbus_rtu_set_rts(modbus_t *ctx, int mode)
             _modbus_rtu_ioctl_rts(ctx->s, ctx_rtu->rts != MODBUS_RTU_RTS_UP);
 
             return 0;
+        } else {
+            errno = EINVAL;
+            return -1;
         }
 #else
         if (ctx->debug) {
--
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