[nrf fromtree] bluetooth: gatt: Add BT_GATT_CCC_WITH_WRITE_CB()

Add simple helper macro so users can define a CCCD with a write cb
without having to combine BT_GATT_CCC_MANAGED() and
BT_GATT_CCC_INITIALIZER() themselves.

Unlike the changed callback the write callback has a return value
that can be used to reject the write request.

Signed-off-by: Olivier Lesage <olivier.lesage@nordicsemi.no>
(cherry picked from commit 7b61bd6)
(cherry picked from commit 336b11a)

Author: olivier-le-sage

include/zephyr/bluetooth/gatt.h

@@ -1167,6 +1167,20 @@ ssize_t bt_gatt_attr_write_ccc(struct bt_conn *conn,
 	BT_GATT_CCC_MANAGED(((struct _bt_gatt_ccc[])			\
 		{BT_GATT_CCC_INITIALIZER(_changed, NULL, NULL)}), _perm)
 
+/**
+ *  @brief Client Characteristic Configuration Declaration Macro with write callback.
+ *
+ *  Helper macro to declare a CCC attribute with a write callback.
+ *
+ *  @param _changed Configuration changed callback.
+ *  @param _write Configuration write callback.
+ *  @param _perm CCC access permissions,
+ *               a bitmap of @ref bt_gatt_perm values.
+ */
+#define BT_GATT_CCC_WITH_WRITE_CB(_changed, _write, _perm)		\
+	BT_GATT_CCC_MANAGED(((struct _bt_gatt_ccc[])			\
+		{BT_GATT_CCC_INITIALIZER(_changed, _write, NULL) }), _perm)
+
 /** @brief Read Characteristic Extended Properties Attribute helper
  *
  *  Read CEP attribute value from local database storing the result into buffer

tests/bluetooth/gatt/src/main.c

@@ -39,6 +39,11 @@ static void test1_ccc_cfg_changed(const struct bt_gatt_attr *attr, uint16_t valu
 	nfy_enabled = (value == BT_GATT_CCC_NOTIFY) ? 1 : 0;
 }
 
+static ssize_t test1_ccc_cfg_write_cb(struct bt_conn *conn, const struct bt_gatt_attr *attr, uint16_t value)
+{
+	return sizeof(value);
+}
+
 static ssize_t read_test(struct bt_conn *conn, const struct bt_gatt_attr *attr,
 			void *buf, uint16_t len, uint16_t offset)
 {
@@ -507,3 +512,25 @@ ZTEST(test_gatt, test_bt_gatt_err_to_str)
 		zassert_not_null(bt_gatt_err_to_str(-i), ": %d", i);
 	}
 }
+
+ZTEST(test_gatt, test_gatt_ccc_write_cb)
+{
+	struct bt_gatt_attr test_write_cb_attrs[] = {
+		/* Vendor Primary Service Declaration */
+		BT_GATT_PRIMARY_SERVICE(&test1_uuid),
+
+		BT_GATT_CHARACTERISTIC(&test1_nfy_uuid.uuid,
+				       BT_GATT_CHRC_NOTIFY, BT_GATT_PERM_NONE,
+				       NULL, NULL, &nfy_enabled),
+		BT_GATT_CCC_WITH_WRITE_CB(test1_ccc_cfg_changed,
+			test1_ccc_cfg_write_cb,
+			BT_GATT_PERM_READ_ENCRYPT | BT_GATT_PERM_WRITE_ENCRYPT),
+	};
+
+	struct bt_gatt_service test_write_cb_svc = BT_GATT_SERVICE(test_write_cb_attrs);
+
+	zassert_false(bt_gatt_service_register(&test_write_cb_svc),
+		     "Test service registration failed");
+	zassert_false(bt_gatt_service_unregister(&test_write_cb_svc),
+		     "Test service1 unregister failed");
+}

tests/bsim/bluetooth/host/gatt/ccc_store/src/central.c

@@ -41,6 +41,7 @@ static struct bt_conn *default_conn;
 
 static struct bt_conn_cb central_cb;
 
+DEFINE_FLAG_STATIC(gatt_subscribed_rejected_flag);
 DEFINE_FLAG_STATIC(gatt_subscribed_flag);
 
 static uint8_t notify_cb(struct bt_conn *conn, struct bt_gatt_subscribe_params *params,
@@ -69,6 +70,9 @@ static uint8_t notify_cb(struct bt_conn *conn, struct bt_gatt_subscribe_params *
 static void subscribe_cb(struct bt_conn *conn, uint8_t err, struct bt_gatt_subscribe_params *params)
 {
 	if (err) {
+		if (err == BT_ATT_ERR_WRITE_NOT_PERMITTED) {
+			SET_FLAG(gatt_subscribed_rejected_flag);
+		}
 		return;
 	}
 
@@ -81,6 +85,7 @@ static void ccc_subscribe(void)
 {
 	int err;
 
+	UNSET_FLAG(gatt_subscribed_rejected_flag);
 	UNSET_FLAG(gatt_subscribed_flag);
 
 	subscribe_params.notify = notify_cb;
@@ -94,6 +99,13 @@ static void ccc_subscribe(void)
 		TEST_FAIL("Failed to subscribe (att err %d)", err);
 	}
 
+	WAIT_FOR_FLAG(gatt_subscribed_rejected_flag);
+
+	err = bt_gatt_subscribe(default_conn, &subscribe_params);
+	if (err) {
+		TEST_FAIL("Failed to subscribe (att err %d)", err);
+	}
+
 	WAIT_FOR_FLAG(gatt_subscribed_flag);
 }
 

tests/bsim/bluetooth/host/gatt/ccc_store/src/peripheral.c

@@ -41,6 +41,8 @@ static struct bt_conn *default_conn;
 
 static struct bt_conn_cb peripheral_cb;
 
+static bool notif_write_allowed;
+
 static void ccc_cfg_changed(const struct bt_gatt_attr *attr, uint16_t value)
 {
 	ARG_UNUSED(attr);
@@ -52,10 +54,24 @@ static void ccc_cfg_changed(const struct bt_gatt_attr *attr, uint16_t value)
 	SET_FLAG(ccc_cfg_changed_flag);
 }
 
+static ssize_t ccc_cfg_write_cb(struct bt_conn *conn, const struct bt_gatt_attr *attr, uint16_t value)
+{
+	if (notif_write_allowed) {
+		LOG_INF("CCC Write Request accepted.");
+		return sizeof(value);
+	} else {
+		LOG_INF("CCC Write Request rejected.");
+		notif_write_allowed = true;
+		return BT_GATT_ERR(BT_ATT_ERR_WRITE_NOT_PERMITTED);
+	}
+}
+
 BT_GATT_SERVICE_DEFINE(dummy_svc, BT_GATT_PRIMARY_SERVICE(&dummy_service),
 		       BT_GATT_CHARACTERISTIC(&notify_characteristic_uuid.uuid, BT_GATT_CHRC_NOTIFY,
 					      BT_GATT_PERM_NONE, NULL, NULL, NULL),
-		       BT_GATT_CCC(ccc_cfg_changed, BT_GATT_PERM_READ | BT_GATT_PERM_WRITE));
+		       BT_GATT_CCC_WITH_WRITE_CB(ccc_cfg_changed, ccc_cfg_write_cb,
+						 BT_GATT_PERM_READ | BT_GATT_PERM_WRITE)
+);
 
 static void create_adv(struct bt_le_ext_adv **adv)
 {