greybus: define operation_cancel()

Define a new function operation_cancel() that cancels an
outstanding operation.  Use it to clear out any operations that
might be pending at the time a connection is torn down.

Note:  This code isn't really functional yet, partially because
greybus_kill_gbuf() is not implemented.
Signed-off-by: Alex Elder <elder@linaro.org>
Signed-off-by: Greg Kroah-Hartman <greg@kroah.com>

drivers/staging/greybus/connection.c

@@ -162,12 +162,19 @@ struct gb_connection *gb_connection_create(struct gb_interface *interface,
  */
 void gb_connection_destroy(struct gb_connection *connection)
 {
+	struct gb_operation *operation;
+	struct gb_operation *next;
+
 	if (WARN_ON(!connection))
 		return;
 
 	/* XXX Need to wait for any outstanding requests to complete */
 	WARN_ON(!list_empty(&connection->operations));
 
+	list_for_each_entry_safe(operation, next, &connection->operations,
+					links) {
+		gb_operation_cancel(operation);
+	}
 	spin_lock_irq(&gb_connections_lock);
 	list_del(&connection->interface_links);
 	_gb_hd_connection_remove(connection);

drivers/staging/greybus/operation.c

@@ -501,6 +501,24 @@ void gb_connection_operation_recv(struct gb_connection *connection,
 	queue_work(gb_operation_recv_workqueue, &operation->recv_work);
 }
 
+/*
+ * Cancel an operation.
+ */
+void gb_operation_cancel(struct gb_operation *operation)
+{
+	int ret;
+
+	operation->canceled = true;
+	ret = greybus_kill_gbuf(operation->request);
+	if (ret)
+		pr_warn("error %d killing request gbuf\n", ret);
+	if (operation->response) {
+		ret = greybus_kill_gbuf(operation->response);
+		if (ret)
+			pr_warn("error %d killing response gbuf\n", ret);
+	}
+}
+
 int gb_operation_init(void)
 {
 	gb_operation_cache = kmem_cache_create("gb_operation_cache",

drivers/staging/greybus/operation.h

@@ -55,6 +55,7 @@ struct gb_operation {
 	struct gbuf		*request;
 	struct gbuf		*response;
 	u16			id;
+	bool			canceled;
 
 	u8			result;
 	struct work_struct	recv_work;
@@ -81,6 +82,7 @@ int gb_operation_request_send(struct gb_operation *operation,
 				gb_operation_callback callback);
 int gb_operation_response_send(struct gb_operation *operation);
 
+void gb_operation_cancel(struct gb_operation *operation);
 int gb_operation_wait(struct gb_operation *operation);
 void gb_operation_complete(struct gb_operation *operation);