[RFC 4/6] greybus: add API for async unidirectional transfer

["Damien Riégel" <damien.riegel@silabs.com>]

This adds a helper function for unidirectional asynchronous transfer.
This is just for convenience as some drivers do these steps manually,
like the loopback driver in gb_loopback_async_operation().

Signed-off-by: Damien Riégel <damien.riegel@silabs.com>
---
 drivers/greybus/operation.c       | 52 +++++++++++++++++++++++++++++++
 include/linux/greybus/operation.h |  4 +++
 2 files changed, 56 insertions(+)

diff --git a/drivers/greybus/operation.c b/drivers/greybus/operation.c
index 8459e9bc074..a599b9d36cf 100644
--- a/drivers/greybus/operation.c
+++ b/drivers/greybus/operation.c
@@ -1174,6 +1174,58 @@ int gb_operation_sync_timeout(struct gb_connection *connection, int type,
 }
 EXPORT_SYMBOL_GPL(gb_operation_sync_timeout);
 
+/**
+ * gb_operation_unidirectional_async_timeout() - initiate an asynchronous unidirectional operation
+ * @connection:		connection to use
+ * @callback:		function called when operation completes
+ * @data:		user-data, retrieved with gb_operation_get_data()
+ * @type:		type of operation to send
+ * @request:		memory buffer to copy the request from
+ * @request_size:	size of @request
+ * @timeout:		send timeout in milliseconds
+ *
+ * Initiate a unidirectional operation by sending a request message. Completion is notified by the
+ * user-provided callback. User can determine operation status with gb_operation_result().
+ * operation must be released with gb_operation_put().
+ *
+ * Note that successful send of a unidirectional operation does not imply that
+ * the request as actually reached the remote end of the connection.
+ */
+int gb_operation_unidirectional_async_timeout(struct gb_connection *connection,
+					      gb_operation_callback callback, void *data,
+					      int type, void *request, int request_size,
+					      unsigned int timeout)
+{
+	struct gb_operation *operation;
+	int ret;
+
+	if (request_size && !request)
+		return -EINVAL;
+
+	operation = gb_operation_create_flags(connection, type,
+					      request_size, 0,
+					      GB_OPERATION_FLAG_UNIDIRECTIONAL,
+					      GFP_KERNEL);
+	if (!operation)
+		return -ENOMEM;
+
+	gb_operation_set_data(operation, data);
+
+	if (request_size)
+		memcpy(operation->request->payload, request, request_size);
+
+	ret = gb_operation_request_send(operation, callback, timeout, GFP_KERNEL);
+	if (ret) {
+		dev_err(&connection->hd->dev,
+			"%s: asynchronous operation id 0x%04x of type 0x%02x failed: %d\n",
+			connection->name, operation->id, type, ret);
+		gb_operation_put(operation);
+	}
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(gb_operation_unidirectional_async_timeout);
+
 /**
  * gb_operation_unidirectional_timeout() - initiate a unidirectional operation
  * @connection:		connection to use
diff --git a/include/linux/greybus/operation.h b/include/linux/greybus/operation.h
index cb8e4ef4522..01dd1d89d89 100644
--- a/include/linux/greybus/operation.h
+++ b/include/linux/greybus/operation.h
@@ -192,6 +192,10 @@ int gb_operation_sync_timeout(struct gb_connection *connection, int type,
 				void *request, int request_size,
 				void *response, int response_size,
 				unsigned int timeout);
+int gb_operation_unidirectional_async_timeout(struct gb_connection *connection,
+					      gb_operation_callback callback, void *data,
+					      int type, void *request, int request_size,
+					      unsigned int timeout);
 int gb_operation_unidirectional_timeout(struct gb_connection *connection,
 				int type, void *request, int request_size,
 				unsigned int timeout);
-- 
2.49.0