From 2cff3ac0ee43b0412a82da764feb5d348aa9cc44 Mon Sep 17 00:00:00 2001
From: aleks <aleks@espressif.com>
Date: Mon, 4 May 2026 08:58:09 +0200
Subject: [PATCH] fix: address maximum api blocking time

---
 Kconfig                                        | 13 ++++++++++++-
 .../mb_controller/common/esp_modbus_master.c   |  9 ++++++++-
 modbus/mb_controller/common/mbc_master.h       | 18 ++++++++++++++----
 3 files changed, 34 insertions(+), 6 deletions(-)

diff --git a/Kconfig b/Kconfig
index f799740..514f989 100644
--- a/Kconfig
+++ b/Kconfig
@@ -71,12 +71,23 @@ menu "Modbus configuration"
 
     config FMB_MASTER_TIMEOUT_MS_RESPOND
         int "Slave respond timeout (Milliseconds)"
-        default 10000
+        default 5000
         range 150 30000
         help
                 If master sends a frame which is not broadcast, it has to wait some time for slave response.
                 if slave is not respond in this time, the master will process timeout error.
 
+    config FMB_MASTER_MAX_API_BLOCKING_TIME_MS
+        int "Modbus TCP master API blocking threshold (ms)"
+        range 3000 200000
+        default 6000
+        help
+                This option represents the maximum API blocking time used by controller API calls.
+                The master uses timer to handle slave response timeout as defined by FMB_MASTER_TIMEOUT_MS_RESPOND
+                or overridden by corresponded master configuration field. The actual API blocking time is determined
+                as a shortest time between these two values. This API blocking time is separated with
+                FMB_MASTER_TIMEOUT_MS_RESPOND intentionally to prevent possible misconfiguration and must not be less than it.
+
     config FMB_MASTER_DELAY_MS_CONVERT
         int "Slave conversion delay (Milliseconds)"
         default 200
diff --git a/modbus/mb_controller/common/esp_modbus_master.c b/modbus/mb_controller/common/esp_modbus_master.c
index 1d9010b..e0072d4 100644
--- a/modbus/mb_controller/common/esp_modbus_master.c
+++ b/modbus/mb_controller/common/esp_modbus_master.c
@@ -1,5 +1,5 @@
 /*
- * SPDX-FileCopyrightText: 2016-2023 Espressif Systems (Shanghai) CO LTD
+ * SPDX-FileCopyrightText: 2016-2026 Espressif Systems (Shanghai) CO LTD
  *
  * SPDX-License-Identifier: Apache-2.0
  */
@@ -203,6 +203,13 @@ esp_err_t mbc_master_start(void *ctx)
     MB_RETURN_ON_FALSE(ctx, ESP_ERR_INVALID_STATE, TAG,
                        "Master interface is not correctly initialized.");
     mbm_controller_iface_t *mbm_controller = MB_MASTER_GET_IFACE(ctx);
+
+    if ((mbm_controller->opts.comm_opts.common_opts.response_tout_ms > 0) &&
+            (mbm_controller->opts.comm_opts.common_opts.response_tout_ms > CONFIG_FMB_MASTER_MAX_API_BLOCKING_TIME_MS)) {
+        mbm_controller->opts.comm_opts.common_opts.response_tout_ms = CONFIG_FMB_MASTER_MAX_API_BLOCKING_TIME_MS + 500;
+        ESP_LOGW(TAG, "Slave response time option in master is incorrect, setting to max value.");
+    }
+
     MB_RETURN_ON_FALSE(mbm_controller->start, ESP_ERR_INVALID_STATE, TAG,
                        "Master interface is not correctly initialized.");
     error = mbm_controller->start(ctx);
diff --git a/modbus/mb_controller/common/mbc_master.h b/modbus/mb_controller/common/mbc_master.h
index 40d8073..837d57d 100644
--- a/modbus/mb_controller/common/mbc_master.h
+++ b/modbus/mb_controller/common/mbc_master.h
@@ -1,5 +1,5 @@
 /*
- * SPDX-FileCopyrightText: 2016-2023 Espressif Systems (Shanghai) CO LTD
+ * SPDX-FileCopyrightText: 2016-2026 Espressif Systems (Shanghai) CO LTD
  *
  * SPDX-License-Identifier: Apache-2.0
  */
@@ -22,16 +22,26 @@
 #include "mb_utils.h"
 #include "mb_master.h"
 
+#include "sdkconfig.h"
+
 #ifdef __cplusplus
 extern "C" {
 #endif
 
 /* ----------------------- Defines ------------------------------------------*/
+#define MB_MIN_RESP_DELAY_MS (300)
 
 // Set the maximum resource waiting time, the actual time of resource release
-// will be dependent on response time set by timer + conversion time if the command is received
-#define MB_MAX_RESP_DELAY_MS (3000)
-#define MB_MIN_RESP_DELAY_MS (300)
+// will be dependent on response time set by timer + conversion time if the command is received.
+#if defined(CONFIG_FMB_MASTER_MAX_API_BLOCKING_TIME_MS)
+#define MB_MAX_RESP_DELAY_MS (CONFIG_FMB_MASTER_MAX_API_BLOCKING_TIME_MS)
+_Static_assert(
+    (CONFIG_FMB_MASTER_MAX_API_BLOCKING_TIME_MS) >= (CONFIG_FMB_MASTER_TIMEOUT_MS_RESPOND),
+    "CONFIG_FMB_MASTER_MAX_API_BLOCKING_TIME_MS must be >= CONFIG_FMB_MASTER_TIMEOUT_MS_RESPOND"
+);
+#else
+#define MB_MAX_RESP_DELAY_MS (CONFIG_FMB_MASTER_TIMEOUT_MS_RESPOND)
+#endif
 
 /**
  * @brief Modbus controller handler structure