From f8cb9f7286d3db3e1287f5024c7521411638e8ce Mon Sep 17 00:00:00 2001
From: David Cermak <cermak@espressif.com>
Date: Mon, 17 Jan 2022 10:47:59 +0100
Subject: [PATCH] mqtt: Add docs on MQTT_CUSTOM_OUTBOX implentation

Closes https://github.com/espressif/esp-mqtt/issues/217
---
 components/mqtt/Kconfig | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/components/mqtt/Kconfig b/components/mqtt/Kconfig
index 9a06e43..fd1d4a6 100644
--- a/components/mqtt/Kconfig
+++ b/components/mqtt/Kconfig
@@ -137,8 +137,12 @@ menu "ESP-MQTT Configurations"
         bool "Enable custom outbox implementation"
         default n
         help
-            Set to true if a specific implementation of message outbox is needed (e.g. persistant outbox in NVM or
+            Set to true if a specific implementation of message outbox is needed (e.g. persistent outbox in NVM or
             similar).
+            Note: Implementation of the custom outbox must be added to the mqtt component. These CMake commands
+            could be used to append the custom implementation to lib-mqtt sources:
+            idf_component_get_property(mqtt mqtt COMPONENT_LIB)
+            set_property(TARGET ${mqtt} PROPERTY SOURCES ${PROJECT_DIR}/custom_outbox.c APPEND)
 
     config MQTT_OUTBOX_EXPIRED_TIMEOUT_MS
         int "Outbox message expired timeout[ms]"