feat: Allows esp-mqtt task and work buffers to be allocated in external memory

lib/include/mqtt_config.h

@@ -1,5 +1,5 @@
 /*
- * SPDX-FileCopyrightText: 2025 Espressif Systems (Shanghai) CO LTD
+ * SPDX-FileCopyrightText: 2025-2026 Espressif Systems (Shanghai) CO LTD
  *
  * SPDX-License-Identifier: Apache-2.0
  */
@@ -96,6 +96,12 @@
 #endif
 #endif
 
+#if MQTT_CORE_SELECTION_ENABLED
+#define MQTT_TASK_AFFINITY MQTT_TASK_CORE
+#else
+#define MQTT_TASK_AFFINITY tskNO_AFFINITY
+#endif
+
 #ifdef  CONFIG_MQTT_OUTBOX_EXPIRED_TIMEOUT_MS
 #define OUTBOX_EXPIRED_TIMEOUT_MS   CONFIG_MQTT_OUTBOX_EXPIRED_TIMEOUT_MS
 #else
@@ -119,5 +125,17 @@
 #define MQTT_OUTBOX_MEMORY MALLOC_CAP_DEFAULT
 #endif
 
+#ifdef CONFIG_MQTT_BUFFERS_ON_EXTERNAL_MEMORY
+#define MQTT_BUFFER_MEMORY MALLOC_CAP_SPIRAM
+#else
+#define MQTT_BUFFER_MEMORY MALLOC_CAP_DEFAULT
+#endif
+
+#ifdef CONFIG_MQTT_TASK_STACK_ON_EXTERNAL_MEMORY
+#define MQTT_TASK_STACK_ON_EXTERNAL_MEMORY 1
+#else
+#define MQTT_TASK_STACK_ON_EXTERNAL_MEMORY 0
+#endif
+
 #define OUTBOX_MAX_SIZE             (4*1024)
 #endif

lib/mqtt_msg.c

@@ -4,6 +4,7 @@
  * SPDX-License-Identifier: BSD-3-Clause
  */
 #include <string.h>
+#include "esp_heap_caps.h"
 #include "mqtt_client.h"
 #include "mqtt_msg.h"
 #include "mqtt_config.h"
@@ -633,7 +634,7 @@ int mqtt_has_valid_msg_hdr(uint8_t *buffer, size_t length)
 esp_err_t mqtt_msg_buffer_init(mqtt_connection_t *connection, int buffer_size)
 {
     memset(&connection->outbound_message, 0, sizeof(mqtt_message_t));
-    connection->buffer = (uint8_t *)calloc(buffer_size, sizeof(uint8_t));
+    connection->buffer = (uint8_t *)heap_caps_calloc(buffer_size, sizeof(uint8_t), MQTT_BUFFER_MEMORY);
 
     if (!connection->buffer) {
         return ESP_ERR_NO_MEM;