Bluetooth: Host: Fix type mismatch in bt_gatt_cancel

`bt_gatt_cancel` takes a `bt_gatt_.._params` pointer. The `params`
pointer is mistakenly passed on to `bt_att_req_cancel`, which expects a
`bt_att_req`.

This change makes bt_gatt_cancel locate the `req` and pass that to
`bt_att_req_cancel`.

Signed-off-by: Aleksander Wasaznik <aleksander.wasaznik@nordicsemi.no>
Co-authored-by: Emil Gydesen <Thalley@users.noreply.github.com>

include/bluetooth/gatt.h

@@ -1675,10 +1675,22 @@ int bt_gatt_resubscribe(uint8_t id, const bt_addr_le_t *peer,
 int bt_gatt_unsubscribe(struct bt_conn *conn,
 			struct bt_gatt_subscribe_params *params);
 
-/** @brief Cancel GATT pending request
+/** @brief Try to cancel the first pending request identified by @p params.
  *
- *  @param conn Connection object.
+ *  This function does not release @p params for reuse. The usual callbacks
- *  @param params Requested params address.
+ *  for the request still apply. A successful cancel simulates a
+ *  #BT_ATT_ERR_UNLIKELY response from the server.
+ *
+ *  This function can cancel the following request functions:
+ *   - #bt_gatt_exchange_mtu
+ *   - #bt_gatt_discover
+ *   - #bt_gatt_read
+ *   - #bt_gatt_write
+ *   - #bt_gatt_subscribe
+ *   - #bt_gatt_unsubscribe
+ *
+ *  @param conn The connection the request was issued on.
+ *  @param params The address `params` used in the request function call.
  */
 void bt_gatt_cancel(struct bt_conn *conn, void *params);
 

subsys/bluetooth/host/att.c

@@ -3228,3 +3228,29 @@ void bt_att_req_cancel(struct bt_conn *conn, struct bt_att_req *req)
 
 	bt_att_req_free(req);
 }
+
+struct bt_att_req *bt_att_find_req_by_user_data(struct bt_conn *conn, const void *user_data)
+{
+	struct bt_att *att;
+	struct bt_att_chan *chan;
+	struct bt_att_req *req;
+
+	att = att_get(conn);
+	if (!att) {
+		return NULL;
+	}
+
+	SYS_SLIST_FOR_EACH_CONTAINER(&att->chans, chan, node) {
+		if (chan->req->user_data == user_data) {
+			return chan->req;
+		}
+	}
+
+	SYS_SLIST_FOR_EACH_CONTAINER(&att->reqs, req, node) {
+		if (req->user_data == user_data) {
+			return req;
+		}
+	}
+
+	return NULL;
+}

subsys/bluetooth/host/att_internal.h

@@ -304,3 +304,10 @@ int bt_eatt_connect(struct bt_conn *conn, uint8_t num_channels);
 
 /* Disconnect EATT channels */
 int bt_eatt_disconnect(struct bt_conn *conn);
+
+/** @brief Find a pending ATT request by its user_data pointer.
+ *  @param conn The connection the request was issued on.
+ *  @param user_data The pointer value to look for.
+ *  @return The found request. NULL if not found.
+ */
+struct bt_att_req *bt_att_find_req_by_user_data(struct bt_conn *conn, const void *user_data);

subsys/bluetooth/host/gatt.c

@@ -4650,7 +4650,22 @@ int bt_gatt_unsubscribe(struct bt_conn *conn,
 
 void bt_gatt_cancel(struct bt_conn *conn, void *params)
 {
-	bt_att_req_cancel(conn, params);
+	struct bt_att_req *req;
+	bt_att_func_t func = NULL;
+
+	k_sched_lock();
+
+	req = bt_att_find_req_by_user_data(conn, params);
+	if (req) {
+		func = req->func;
+		bt_att_req_cancel(conn, req);
+	}
+
+	k_sched_unlock();
+
+	if (func) {
+		func(conn, BT_ATT_ERR_UNLIKELY, NULL, 0, params);
+	}
 }
 
 static void add_subscriptions(struct bt_conn *conn)