[nrf fromtree] bluetooth: host: Add bt_gatt_cb_unregister() to unregister GATT callbacks

New API bt_gatt_cb_unregister, use _SAFE iteration for callback list.

Signed-off-by: Zhijie Zhong <[email protected]>
(cherry picked from commit c222dcf)

Author: zhongzhijie1

doc/releases/release-notes-4.4.rst

@@ -65,6 +65,12 @@ Deprecated APIs and options
 New APIs and options
 ====================
 
+* Bluetooth
+
+  * Host
+
+    * :c:func:`bt_gatt_cb_unregister` Added an API to unregister GATT callback handlers.
+
 ..
   Link to new APIs here, in a group if you think it's necessary, no need to get
   fancy just list the link, that should contain the documentation. If you feel

include/zephyr/bluetooth/gatt.h

@@ -622,6 +622,17 @@ static inline const char *bt_gatt_err_to_str(int gatt_err)
  */
 void bt_gatt_cb_register(struct bt_gatt_cb *cb);
 
+/** @brief Unregister GATT callbacks.
+ *
+ *  Unregister callbacks for monitoring the state of GATT. The callback
+ *  struct should be one that was previously registered.
+ *
+ *  @param cb Callback struct.
+ *
+ *  @return 0 in case of success or negative value in case of error.
+ */
+int bt_gatt_cb_unregister(struct bt_gatt_cb *cb);
+
 /** @brief Register GATT authorization callbacks.
  *
  *  Register callbacks to perform application-specific authorization of GATT

subsys/bluetooth/host/gatt.c

@@ -1628,6 +1628,19 @@ void bt_gatt_cb_register(struct bt_gatt_cb *cb)
 	sys_slist_append(&callback_list, &cb->node);
 }
 
+int bt_gatt_cb_unregister(struct bt_gatt_cb *cb)
+{
+	if (cb == NULL) {
+		return -EINVAL;
+	}
+
+	if (!sys_slist_find_and_remove(&callback_list, &cb->node)) {
+		return -ENOENT;
+	}
+
+	return 0;
+}
+
 #if defined(CONFIG_BT_GATT_DYNAMIC_DB)
 static void db_changed(void)
 {
@@ -6023,9 +6036,9 @@ void bt_gatt_connected(struct bt_conn *conn)
 
 void bt_gatt_att_max_mtu_changed(struct bt_conn *conn, uint16_t tx, uint16_t rx)
 {
-	struct bt_gatt_cb *cb;
+	struct bt_gatt_cb *cb, *tmp;
 
-	SYS_SLIST_FOR_EACH_CONTAINER(&callback_list, cb, node) {
+	SYS_SLIST_FOR_EACH_CONTAINER_SAFE(&callback_list, cb, tmp, node) {
 		if (cb->att_mtu_updated) {
 			cb->att_mtu_updated(conn, tx, rx);
 		}