From de7840be25ee089eb3ca7e4695da2331214e8e89 Mon Sep 17 00:00:00 2001
From: Deomid Ryabkov <rojer@cesanta.com>
Date: Fri, 14 Dec 2018 22:43:21 +0000
Subject: [PATCH] Refactored BT GATTS API, added mJS bindings

All the ESP32 specifics are hidden in the implementation, new API is
generic and is much easier to use:

 * Prepared writes are handled by mos, user doesn't need to care about reassembling the write.
 * Notification handling is much simpler - CCCD management is handled by mos, user gets simple "notifications on/off" event.
 * ESP32 code cleaned up, all processing moved to main task.

Updated existing GATTS service implementations to use it.

CL: Refactored BT GATTS API, added mJS bindings

PUBLISHED_FROM=7f1a63102d207b68baf1f50b6b9e7fd7c175f35b
---
 mos.yml                         |   4 +
 mos_esp32.yml                   |   2 -
 src/esp32/esp32_bt_svc_config.c | 343 --------------------------------
 src/mgos_bt_svc_config.c        | 295 +++++++++++++++++++++++++++
 4 files changed, 299 insertions(+), 345 deletions(-)
 delete mode 100644 mos_esp32.yml
 delete mode 100644 src/esp32/esp32_bt_svc_config.c
 create mode 100644 src/mgos_bt_svc_config.c

diff --git a/mos.yml b/mos.yml
index 0cb0955..a76a4a8 100644
--- a/mos.yml
+++ b/mos.yml
@@ -3,11 +3,15 @@ description: Configuration over Bluetooth GATT service support
 type: lib
 version: 1.0
 
+sources:
+  - src
+
 libs:
   - origin: https://github.com/mongoose-os-libs/bt-common
 
 config_schema:
   - ["bt.config_svc_enable", "b", true, {title: "Enable the config service"}]
+  - ["bt.config_svc_sec_level", "i", 0, {title: "Minimum required security level"}]
 
 tags:
   - bt
diff --git a/mos_esp32.yml b/mos_esp32.yml
deleted file mode 100644
index eedd0d3..0000000
--- a/mos_esp32.yml
+++ /dev/null
@@ -1,2 +0,0 @@
-sources:
-  - src/esp32
diff --git a/src/esp32/esp32_bt_svc_config.c b/src/esp32/esp32_bt_svc_config.c
deleted file mode 100644
index 6200c84..0000000
--- a/src/esp32/esp32_bt_svc_config.c
+++ /dev/null
@@ -1,343 +0,0 @@
-/*
- * Copyright (c) 2014-2018 Cesanta Software Limited
- * All rights reserved
- *
- * Licensed under the Apache License, Version 2.0 (the ""License"");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *     http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an ""AS IS"" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-/*
- * Interface to sys_config over BLE GATT service.
- * See README.md for high-level description.
- */
-
-#include <stdlib.h>
-
-#include "common/cs_dbg.h"
-#include "common/mbuf.h"
-#include "common/mg_str.h"
-
-#include "mgos_config_util.h"
-#include "mgos_hal.h"
-#include "mgos_sys_config.h"
-#include "mgos_utils.h"
-
-#include "esp32_bt_gatts.h"
-
-/* Note: UUIDs below are in reverse, because that's how ESP wants them. */
-static const esp_bt_uuid_t mos_cfg_svc_uuid = {
-    .len = ESP_UUID_LEN_128,
-    .uuid.uuid128 =
-        {
-         /* _mOS_CFG_SVC_ID_, 5f6d4f53-5f43-4647-5f53-56435f49445f */
-         0x5f, 0x44, 0x49, 0x5f, 0x43, 0x56, 0x53, 0x5f, 0x47, 0x46, 0x43, 0x5f,
-         0x53, 0x4f, 0x6d, 0x5f,
-        },
-};
-
-static const esp_bt_uuid_t mos_cfg_key_uuid = {
-    .len = ESP_UUID_LEN_128,
-    .uuid.uuid128 =
-        {
-         /* 0mOS_CFG_key___0, 306d4f53-5f43-4647-5f6b-65795f5f5f30 */
-         0x30, 0x5f, 0x5f, 0x5f, 0x79, 0x65, 0x6b, 0x5f, 0x47, 0x46, 0x43, 0x5f,
-         0x53, 0x4f, 0x6d, 0x30,
-        },
-};
-static uint16_t mos_cfg_key_ah;
-
-static const esp_bt_uuid_t mos_cfg_value_uuid = {
-    .len = ESP_UUID_LEN_128,
-    .uuid.uuid128 =
-        {
-         /* 1mOS_CFG_value_1, 316d4f53-5f43-4647-5f76-616c75655f31 */
-         0x31, 0x5f, 0x65, 0x75, 0x6c, 0x61, 0x76, 0x5f, 0x47, 0x46, 0x43, 0x5f,
-         0x53, 0x4f, 0x6d, 0x31,
-        },
-};
-static uint16_t mos_cfg_value_ah;
-
-static const esp_bt_uuid_t mos_cfg_save_uuid = {
-    .len = ESP_UUID_LEN_128,
-    .uuid.uuid128 =
-        {
-         /* 2mOS_CFG_save__2, 326d4f53-5f43-4647-5f73-6176655f5f32 */
-         0x32, 0x5f, 0x5f, 0x65, 0x76, 0x61, 0x73, 0x5f, 0x47, 0x46, 0x43, 0x5f,
-         0x53, 0x4f, 0x6d, 0x32,
-        },
-};
-static uint16_t mos_cfg_save_ah;
-
-const esp_gatts_attr_db_t mos_cfg_gatt_db[7] = {
-    {
-     .attr_control = {.auto_rsp = ESP_GATT_AUTO_RSP},
-     .att_desc =
-         {
-          .uuid_length = ESP_UUID_LEN_16,
-          .uuid_p = (uint8_t *) &primary_service_uuid,
-          .perm = ESP_GATT_PERM_READ,
-          .max_length = ESP_UUID_LEN_128,
-          .length = ESP_UUID_LEN_128,
-          .value = (uint8_t *) mos_cfg_svc_uuid.uuid.uuid128,
-         },
-    },
-
-    /* key */
-    {{ESP_GATT_AUTO_RSP},
-     {ESP_UUID_LEN_16, (uint8_t *) &char_decl_uuid, ESP_GATT_PERM_READ, 1, 1,
-      (uint8_t *) &char_prop_write}},
-    {{ESP_GATT_RSP_BY_APP},
-     {ESP_UUID_LEN_128, (uint8_t *) mos_cfg_key_uuid.uuid.uuid128,
-      ESP_GATT_PERM_WRITE, 0, 0, NULL}},
-
-    /* value */
-    {{ESP_GATT_AUTO_RSP},
-     {ESP_UUID_LEN_16, (uint8_t *) &char_decl_uuid, ESP_GATT_PERM_READ, 1, 1,
-      (uint8_t *) &char_prop_read_write}},
-    {{ESP_GATT_RSP_BY_APP},
-     {ESP_UUID_LEN_128, (uint8_t *) mos_cfg_value_uuid.uuid.uuid128,
-      ESP_GATT_PERM_READ | ESP_GATT_PERM_WRITE, 0, 0, NULL}},
-
-    /* save */
-    {{ESP_GATT_AUTO_RSP},
-     {ESP_UUID_LEN_16, (uint8_t *) &char_decl_uuid, ESP_GATT_PERM_READ, 1, 1,
-      (uint8_t *) &char_prop_write}},
-    {{ESP_GATT_RSP_BY_APP},
-     {ESP_UUID_LEN_128, (uint8_t *) mos_cfg_save_uuid.uuid.uuid128,
-      ESP_GATT_PERM_WRITE, 0, 0, NULL}},
-};
-
-enum bt_cfg_state {
-  BT_CFG_STATE_KEY_ENTRY = 0,
-  BT_CFG_STATE_VALUE_ENTRY = 1,
-  BT_CFG_STATE_VALUE_READ = 2,
-  BT_CFG_STATE_SAVE = 3,
-};
-
-struct bt_cfg_svc_data {
-  struct mbuf key;
-  struct mbuf value;
-  enum bt_cfg_state state;
-};
-
-static bool mgos_bt_svc_config_set(struct bt_cfg_svc_data *sd) {
-  bool ret = false;
-  const struct mgos_conf_entry *e = mgos_conf_find_schema_entry_s(
-      mg_mk_str_n(sd->key.buf, sd->key.len), mgos_config_schema());
-  if (e == NULL) {
-    LOG(LL_ERROR,
-        ("Config key '%.*s' not found", (int) sd->key.len, sd->key.buf));
-    return false;
-  }
-  /* Make sure value is NUL-terminated, for simplicity. */
-  mbuf_append(&sd->value, "", 1);
-  sd->value.len--;
-  const char *vt = NULL;
-  char *vp = (((char *) &mgos_sys_config) + e->offset);
-  /* For simplicity, we only allow setting leaf values. */
-  switch (e->type) {
-    case CONF_TYPE_INT: {
-      int *ivp = (int *) vp;
-      char *endptr = NULL;
-      int v = strtol(sd->value.buf, &endptr, 0);
-      vt = "int";
-      if (endptr - sd->value.buf == sd->value.len) {
-        *ivp = v;
-        ret = true;
-        LOG(LL_INFO, ("'%.*s' = %d", (int) sd->key.len, sd->key.buf, *ivp));
-      }
-      break;
-    }
-    case CONF_TYPE_DOUBLE: {
-      double *dvp = (double *) vp;
-      char *endptr = NULL;
-      double v = strtod(sd->value.buf, &endptr);
-      vt = "float";
-      if (endptr - sd->value.buf == sd->value.len) {
-        *dvp = v;
-        ret = true;
-        LOG(LL_INFO, ("'%.*s' = %f", (int) sd->key.len, sd->key.buf, *dvp));
-      }
-      break;
-    }
-    case CONF_TYPE_STRING: {
-      vt = "string";
-      char **svp = (char **) vp;
-      mgos_conf_set_str(svp, sd->value.buf);
-      LOG(LL_INFO, ("'%.*s' = '%s'", (int) sd->key.len, sd->key.buf,
-                    (*svp ? *svp : "")));
-      ret = true;
-      break;
-    }
-    case CONF_TYPE_BOOL: {
-      bool *bvp = (bool *) vp;
-      const struct mg_str vs = mg_mk_str_n(sd->value.buf, sd->value.len);
-      vt = "bool";
-      if (mg_vcmp(&vs, "true") == 0 || mg_vcmp(&vs, "false") == 0) {
-        *bvp = (mg_vcmp(&vs, "true") == 0);
-        LOG(LL_INFO, ("'%.*s' = %s", (int) sd->key.len, sd->key.buf,
-                      (*bvp ? "true" : "false")));
-        ret = true;
-      }
-      break;
-    }
-    case CONF_TYPE_OBJECT: {
-      LOG(LL_ERROR, ("Setting objects is not allowed (%.*s)", (int) sd->key.len,
-                     sd->key.buf));
-      break;
-    }
-  }
-  if (!ret && vt != NULL) {
-    LOG(LL_ERROR, ("'%.*s': invalid %s value '%.*s'", (int) sd->key.len,
-                   sd->key.buf, vt, (int) sd->value.len, sd->value.buf));
-  }
-  return ret;
-}
-
-static bool mgos_bt_svc_config_ev(struct esp32_bt_session *bs,
-                                  esp_gatts_cb_event_t ev,
-                                  esp_ble_gatts_cb_param_t *ep) {
-  bool ret = false;
-  struct bt_cfg_svc_data *sd = NULL;
-  struct esp32_bt_connection *bc = NULL;
-  if (bs != NULL) { /* CREAT_ATTR_TAB is not associated with any session. */
-    bc = bs->bc;
-    sd = (struct bt_cfg_svc_data *) bs->user_data;
-  }
-  switch (ev) {
-    case ESP_GATTS_CREAT_ATTR_TAB_EVT: {
-      const struct gatts_add_attr_tab_evt_param *p = &ep->add_attr_tab;
-      uint16_t svch = p->handles[0];
-      mos_cfg_key_ah = p->handles[2];
-      mos_cfg_value_ah = p->handles[4];
-      mos_cfg_save_ah = p->handles[6];
-      LOG(LL_DEBUG, ("svch = %d key_ah = %d value_ah = %d save_ah = %d", svch,
-                     mos_cfg_key_ah, mos_cfg_value_ah, mos_cfg_save_ah));
-      break;
-    }
-    case ESP_GATTS_CONNECT_EVT: {
-      sd = (struct bt_cfg_svc_data *) calloc(1, sizeof(*sd));
-      if (sd == NULL) break;
-      mbuf_init(&sd->key, 0);
-      mbuf_init(&sd->value, 0);
-      sd->state = BT_CFG_STATE_KEY_ENTRY;
-      bs->user_data = sd;
-      break;
-    }
-    case ESP_GATTS_READ_EVT: {
-      const struct gatts_read_evt_param *p = &ep->read;
-      if (sd == NULL || p->handle != mos_cfg_value_ah) break;
-      if (sd->key.len == 0) {
-        LOG(LL_ERROR, ("Key to read is not set"));
-        break;
-      }
-      sd->state = BT_CFG_STATE_VALUE_READ;
-      const struct mgos_conf_entry *e = mgos_conf_find_schema_entry_s(
-          mg_mk_str_n(sd->key.buf, sd->key.len), mgos_config_schema());
-      if (e == NULL) {
-        LOG(LL_ERROR,
-            ("Config key '%.*s' not found", (int) sd->key.len, sd->key.buf));
-        break;
-      }
-      struct mbuf vb;
-      mbuf_init(&vb, 0);
-      mgos_conf_emit_cb(&mgos_sys_config, NULL /* base */, e,
-                        false /* pretty */, &vb, NULL /* cb */,
-                        NULL /* cb_param */);
-      uint16_t to_send = bc->mtu - 1;
-      if (p->offset > vb.len) break;
-      if (vb.len - p->offset < to_send) to_send = vb.len - p->offset;
-      LOG(LL_INFO,
-          ("Read '%.*s' %d @ %d = '%.*s'", (int) sd->key.len, sd->key.buf,
-           (int) to_send, (int) p->offset, (int) to_send, vb.buf + p->offset));
-      esp_gatt_rsp_t rsp = {.attr_value = {.handle = mos_cfg_value_ah,
-                                           .offset = p->offset,
-                                           .len = to_send}};
-      memcpy(rsp.attr_value.value, vb.buf + p->offset, to_send);
-      esp_ble_gatts_send_response(bc->gatt_if, bc->conn_id, p->trans_id,
-                                  ESP_GATT_OK, &rsp);
-      ret = true;
-      mbuf_free(&vb);
-      break;
-    }
-    case ESP_GATTS_WRITE_EVT: {
-      const struct gatts_write_evt_param *p = &ep->write;
-      if (sd == NULL) break;
-      if (p->handle == mos_cfg_key_ah) {
-        if (sd->state != BT_CFG_STATE_KEY_ENTRY) {
-          mbuf_free(&sd->key);
-          mbuf_free(&sd->value);
-          mbuf_init(&sd->key, p->len);
-          sd->state = BT_CFG_STATE_KEY_ENTRY;
-        }
-        mbuf_append(&sd->key, p->value, p->len);
-        LOG(LL_DEBUG, ("Key = '%.*s'", (int) sd->key.len, sd->key.buf));
-        ret = true;
-      } else if (p->handle == mos_cfg_value_ah) {
-        if (sd->state != BT_CFG_STATE_VALUE_ENTRY) {
-          mbuf_free(&sd->value);
-          mbuf_init(&sd->value, p->len);
-          sd->state = BT_CFG_STATE_VALUE_ENTRY;
-        }
-        if (p->len == 1 && p->value[0] == 0) {
-          mbuf_free(&sd->value);
-          mbuf_init(&sd->value, 0);
-        } else {
-          mbuf_append(&sd->value, p->value, p->len);
-        }
-        LOG(LL_DEBUG, ("Value = '%.*s'", (int) sd->value.len,
-                       (sd->value.buf ? sd->value.buf : "")));
-        ret = true;
-      } else if (p->handle == mos_cfg_save_ah) {
-        sd->state = BT_CFG_STATE_SAVE;
-        /* NULL value is a legal value, so we check for state here. */
-        if (sd->key.len > 0 && sd->state != BT_CFG_STATE_VALUE_ENTRY) {
-          ret = mgos_bt_svc_config_set(sd);
-        } else {
-          ret = true; /* Allow save and reboot without setting anything. */
-        }
-        if (ret) {
-          if (p->len == 1 && (p->value[0] == '1' || p->value[0] == '2')) {
-            char *msg = NULL;
-            ret = save_cfg(&mgos_sys_config, &msg);
-            if (!ret) {
-              LOG(LL_ERROR, ("Error saving config: %s", msg));
-            } else if (p->value[0] == '2') {
-              mgos_system_restart_after(100);
-            }
-          }
-        }
-      }
-      break;
-    }
-    case ESP_GATTS_DISCONNECT_EVT: {
-      if (sd != NULL) {
-        mbuf_free(&sd->key);
-        mbuf_free(&sd->value);
-        free(sd);
-        bs->user_data = NULL;
-      }
-      break;
-    }
-    default:
-      break;
-  }
-  return ret;
-}
-
-bool mgos_bt_service_config_init(void) {
-  if (mgos_sys_config_get_bt_config_svc_enable()) {
-    mgos_bt_gatts_register_service(mos_cfg_gatt_db, ARRAY_SIZE(mos_cfg_gatt_db),
-                                   mgos_bt_svc_config_ev);
-  }
-  return true;
-}
diff --git a/src/mgos_bt_svc_config.c b/src/mgos_bt_svc_config.c
new file mode 100644
index 0000000..09f91a8
--- /dev/null
+++ b/src/mgos_bt_svc_config.c
@@ -0,0 +1,295 @@
+/*
+ * Copyright (c) 2014-2018 Cesanta Software Limited
+ * All rights reserved
+ *
+ * Licensed under the Apache License, Version 2.0 (the ""License"");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an ""AS IS"" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+/*
+ * Interface to sys_config over BLE GATT service.
+ * See README.md for high-level description.
+ */
+
+#include <stdlib.h>
+
+#include "common/cs_dbg.h"
+#include "common/mbuf.h"
+#include "common/mg_str.h"
+
+#include "mgos_config_util.h"
+#include "mgos_hal.h"
+#include "mgos_sys_config.h"
+#include "mgos_utils.h"
+
+#include "mgos_bt_gatts.h"
+
+enum bt_cfg_state {
+  BT_CFG_STATE_KEY_ENTRY = 0,
+  BT_CFG_STATE_VALUE_ENTRY = 1,
+  BT_CFG_STATE_VALUE_READ = 2,
+  BT_CFG_STATE_SAVE = 3,
+};
+
+struct bt_cfg_svc_data {
+  struct mbuf key;
+  struct mbuf value;
+  enum bt_cfg_state state;
+};
+
+static bool mgos_bt_svc_config_set(struct bt_cfg_svc_data *sd) {
+  bool ret = false;
+  const struct mgos_conf_entry *e = mgos_conf_find_schema_entry_s(
+      mg_mk_str_n(sd->key.buf, sd->key.len), mgos_config_schema());
+  if (e == NULL) {
+    LOG(LL_ERROR,
+        ("Config key '%.*s' not found", (int) sd->key.len, sd->key.buf));
+    return false;
+  }
+  /* Make sure value is NUL-terminated, for simplicity. */
+  mbuf_append(&sd->value, "", 1);
+  sd->value.len--;
+  const char *vt = NULL;
+  char *vp = (((char *) &mgos_sys_config) + e->offset);
+  /* For simplicity, we only allow setting leaf values. */
+  switch (e->type) {
+    case CONF_TYPE_INT: {
+      int *ivp = (int *) vp;
+      char *endptr = NULL;
+      int v = strtol(sd->value.buf, &endptr, 0);
+      vt = "int";
+      if (endptr - sd->value.buf == sd->value.len) {
+        *ivp = v;
+        ret = true;
+        LOG(LL_INFO, ("'%.*s' = %d", (int) sd->key.len, sd->key.buf, *ivp));
+      }
+      break;
+    }
+    case CONF_TYPE_DOUBLE: {
+      double *dvp = (double *) vp;
+      char *endptr = NULL;
+      double v = strtod(sd->value.buf, &endptr);
+      vt = "float";
+      if (endptr - sd->value.buf == sd->value.len) {
+        *dvp = v;
+        ret = true;
+        LOG(LL_INFO, ("'%.*s' = %f", (int) sd->key.len, sd->key.buf, *dvp));
+      }
+      break;
+    }
+    case CONF_TYPE_STRING: {
+      vt = "string";
+      char **svp = (char **) vp;
+      mgos_conf_set_str(svp, sd->value.buf);
+      LOG(LL_INFO, ("'%.*s' = '%s'", (int) sd->key.len, sd->key.buf,
+                    (*svp ? *svp : "")));
+      ret = true;
+      break;
+    }
+    case CONF_TYPE_BOOL: {
+      bool *bvp = (bool *) vp;
+      const struct mg_str vs = mg_mk_str_n(sd->value.buf, sd->value.len);
+      vt = "bool";
+      if (mg_vcmp(&vs, "true") == 0 || mg_vcmp(&vs, "false") == 0) {
+        *bvp = (mg_vcmp(&vs, "true") == 0);
+        LOG(LL_INFO, ("'%.*s' = %s", (int) sd->key.len, sd->key.buf,
+                      (*bvp ? "true" : "false")));
+        ret = true;
+      }
+      break;
+    }
+    case CONF_TYPE_OBJECT: {
+      LOG(LL_ERROR, ("Setting objects is not allowed (%.*s)", (int) sd->key.len,
+                     sd->key.buf));
+      break;
+    }
+  }
+  if (!ret && vt != NULL) {
+    LOG(LL_ERROR, ("'%.*s': invalid %s value '%.*s'", (int) sd->key.len,
+                   sd->key.buf, vt, (int) sd->value.len, sd->value.buf));
+  }
+  return ret;
+}
+
+static enum mgos_bt_gatt_status mgos_bt_cfg_svc_ev(struct mgos_bt_gatts_conn *c,
+                                                   enum mgos_bt_gatts_ev ev,
+                                                   void *ev_arg,
+                                                   void *handler_arg) {
+  switch (ev) {
+    case MGOS_BT_GATTS_EV_CONNECT: {
+      if (!mgos_sys_config_get_bt_config_svc_enable()) {
+        /* Turned off at runtime. */
+        return MGOS_BT_GATT_STATUS_REQUEST_NOT_SUPPORTED;
+      }
+      struct bt_cfg_svc_data *sd =
+          (struct bt_cfg_svc_data *) calloc(1, sizeof(*sd));
+      if (sd == NULL) return MGOS_BT_GATT_STATUS_INSUF_RESOURCES;
+      mbuf_init(&sd->key, 0);
+      mbuf_init(&sd->value, 0);
+      sd->state = BT_CFG_STATE_KEY_ENTRY;
+      c->user_data = sd;
+      return MGOS_BT_GATT_STATUS_OK;
+    }
+    case MGOS_BT_GATTS_EV_CLOSE: {
+      struct bt_cfg_svc_data *sd = (struct bt_cfg_svc_data *) c->user_data;
+      mbuf_free(&sd->key);
+      mbuf_free(&sd->value);
+      free(sd);
+      return MGOS_BT_GATT_STATUS_OK;
+    }
+    default:
+      break;
+  }
+  return MGOS_BT_GATT_STATUS_REQUEST_NOT_SUPPORTED;
+}
+
+static enum mgos_bt_gatt_status mgos_bt_cfg_key_ev(struct mgos_bt_gatts_conn *c,
+                                                   enum mgos_bt_gatts_ev ev,
+                                                   void *ev_arg,
+                                                   void *handler_arg) {
+  struct bt_cfg_svc_data *sd = (struct bt_cfg_svc_data *) c->user_data;
+  if (ev != MGOS_BT_GATTS_EV_WRITE) {
+    return MGOS_BT_GATT_STATUS_REQUEST_NOT_SUPPORTED;
+  }
+  struct mgos_bt_gatts_write_arg *wa =
+      (struct mgos_bt_gatts_write_arg *) ev_arg;
+  if (sd->state != BT_CFG_STATE_KEY_ENTRY) {
+    mbuf_free(&sd->key);
+    mbuf_free(&sd->value);
+    mbuf_init(&sd->key, wa->data.len);
+    sd->state = BT_CFG_STATE_KEY_ENTRY;
+  }
+  mbuf_append(&sd->key, wa->data.p, wa->data.len);
+  LOG(LL_DEBUG, ("Key = '%.*s'", (int) sd->key.len, sd->key.buf));
+  return MGOS_BT_GATT_STATUS_OK;
+}
+
+static enum mgos_bt_gatt_status mgos_bt_cfg_val_ev(struct mgos_bt_gatts_conn *c,
+                                                   enum mgos_bt_gatts_ev ev,
+                                                   void *ev_arg,
+                                                   void *handler_arg) {
+  struct bt_cfg_svc_data *sd = (struct bt_cfg_svc_data *) c->user_data;
+  if (ev == MGOS_BT_GATTS_EV_READ) {
+    struct mgos_bt_gatts_read_arg *ra =
+        (struct mgos_bt_gatts_read_arg *) ev_arg;
+    if (sd->key.len == 0) {
+      LOG(LL_ERROR, ("Key to read is not set"));
+      return MGOS_BT_GATT_STATUS_READ_NOT_PERMITTED;
+    }
+    sd->state = BT_CFG_STATE_VALUE_READ;
+    const struct mgos_conf_entry *e = mgos_conf_find_schema_entry_s(
+        mg_mk_str_n(sd->key.buf, sd->key.len), mgos_config_schema());
+    if (e == NULL) {
+      LOG(LL_ERROR,
+          ("Config key '%.*s' not found", (int) sd->key.len, sd->key.buf));
+      return MGOS_BT_GATT_STATUS_INVALID_OFFSET;
+    }
+    struct mbuf vb;
+    mbuf_init(&vb, 0);
+    mgos_conf_emit_cb(&mgos_sys_config, NULL /* base */, e, false /* pretty */,
+                      &vb, NULL /* cb */, NULL /* cb_param */);
+    uint16_t to_send = c->gc.mtu - 1;
+    if (ra->offset > vb.len) return MGOS_BT_GATT_STATUS_INVALID_OFFSET;
+    if (vb.len - ra->offset < to_send) to_send = vb.len - ra->offset;
+    struct mg_str data = MG_MK_STR_N(vb.buf + ra->offset, to_send);
+    LOG(LL_INFO,
+        ("Read '%.*s' %d @ %d = '%.*s'", (int) sd->key.len, sd->key.buf,
+         (int) to_send, (int) ra->offset, (int) data.len, data.p));
+    mgos_bt_gatts_send_resp_data(c, ra, data);
+    mbuf_free(&vb);
+    return MGOS_BT_GATT_STATUS_OK;
+  } else if (ev == MGOS_BT_GATTS_EV_WRITE) {
+    struct mgos_bt_gatts_write_arg *wa =
+        (struct mgos_bt_gatts_write_arg *) ev_arg;
+    if (sd->state != BT_CFG_STATE_VALUE_ENTRY) {
+      mbuf_free(&sd->value);
+      mbuf_init(&sd->value, wa->data.len);
+      sd->state = BT_CFG_STATE_VALUE_ENTRY;
+    }
+    if (wa->data.len == 1 && wa->data.p[0] == 0) {
+      mbuf_free(&sd->value);
+      mbuf_init(&sd->value, 0);
+    } else {
+      mbuf_append(&sd->value, wa->data.p, wa->data.len);
+    }
+    LOG(LL_DEBUG, ("Value = '%.*s'", (int) sd->value.len,
+                   (sd->value.buf ? sd->value.buf : "")));
+    return MGOS_BT_GATT_STATUS_OK;
+  }
+  return MGOS_BT_GATT_STATUS_REQUEST_NOT_SUPPORTED;
+}
+
+static enum mgos_bt_gatt_status mgos_bt_cfg_save_ev(
+    struct mgos_bt_gatts_conn *c, enum mgos_bt_gatts_ev ev, void *ev_arg,
+    void *handler_arg) {
+  struct bt_cfg_svc_data *sd = (struct bt_cfg_svc_data *) c->user_data;
+  if (ev != MGOS_BT_GATTS_EV_WRITE) {
+    return MGOS_BT_GATT_STATUS_REQUEST_NOT_SUPPORTED;
+  }
+  struct mgos_bt_gatts_write_arg *wa =
+      (struct mgos_bt_gatts_write_arg *) ev_arg;
+  sd->state = BT_CFG_STATE_SAVE;
+  /* NULL value is a legal value, so we check for state here. */
+  if (sd->key.len > 0 && sd->state != BT_CFG_STATE_VALUE_ENTRY) {
+    if (!mgos_bt_svc_config_set(sd)) {
+      LOG(LL_ERROR, ("Error setting config value"));
+      return MGOS_BT_GATT_STATUS_INVALID_OFFSET;
+    }
+  } else {
+    /* Allow save and reboot without setting anything. */
+  }
+  if (wa->data.len == 1) {
+    char op = wa->data.p[0];
+    if (op != '1' && op != '2') {
+      LOG(LL_ERROR, ("Invalid save action %c", op));
+      return MGOS_BT_GATT_STATUS_INVALID_OFFSET;
+    }
+    char *msg = NULL;
+    if (!save_cfg(&mgos_sys_config, &msg)) {
+      LOG(LL_ERROR, ("Error saving config: %s", msg));
+      return MGOS_BT_GATT_STATUS_INVALID_OFFSET;
+    }
+    if (op == '2') {
+      mgos_system_restart_after(300);
+    }
+  }
+  return MGOS_BT_GATT_STATUS_OK;
+}
+
+static const struct mgos_bt_gatts_char_def s_cfg_svc_def[] = {
+    {
+     .uuid = "306d4f53-5f43-4647-5f6b-65795f5f5f30", /* 0mOS_CFG_key___0 */
+     .prop = MGOS_BT_GATTS_PROP_RWNI(0, 1, 0, 0),
+     .handler = mgos_bt_cfg_key_ev,
+    },
+    {
+     .uuid = "316d4f53-5f43-4647-5f76-616c75655f31", /* 1mOS_CFG_value_1 */
+     .prop = MGOS_BT_GATTS_PROP_RWNI(1, 1, 0, 0),
+     .handler = mgos_bt_cfg_val_ev,
+    },
+    {
+     .uuid = "326d4f53-5f43-4647-5f73-6176655f5f32", /* 2mOS_CFG_save__2 */
+     .prop = MGOS_BT_GATTS_PROP_RWNI(0, 1, 0, 0),
+     .handler = mgos_bt_cfg_save_ev,
+    },
+    {.uuid = NULL},
+};
+
+bool mgos_bt_service_config_init(void) {
+  if (!mgos_sys_config_get_bt_config_svc_enable()) return true;
+  mgos_bt_gatts_register_service(
+      "5f6d4f53-5f43-4647-5f53-56435f49445f", /* _mOS_CFG_SVC_ID_ */
+      (enum mgos_bt_gatt_sec_level)
+          mgos_sys_config_get_bt_config_svc_sec_level(),
+      s_cfg_svc_def, mgos_bt_cfg_svc_ev, NULL);
+  return true;
+}