firewire: cdev: code refactoring to operate event of response

This commit is a preparation to handle time stamp of asynchronous
transaction for user space application.

Link: https://lore.kernel.org/r/20230529113406.986289-8-o-takashi@sakamocchi.jpSigned-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>

drivers/firewire/core-cdev.c

@@ -170,7 +170,9 @@ struct outbound_transaction_event {
 	struct event event;
 	struct client *client;
 	struct outbound_transaction_resource r;
-	struct fw_cdev_event_response response;
+	union {
+		struct fw_cdev_event_response without_tstamp;
+	} rsp;
 };
 
 struct inbound_transaction_event {
@@ -540,7 +542,7 @@ static void complete_transaction(struct fw_card *card, int rcode,
 				 void *payload, size_t length, void *data)
 {
 	struct outbound_transaction_event *e = data;
-	struct fw_cdev_event_response *rsp = &e->response;
+	struct fw_cdev_event_response *rsp = &e->rsp.without_tstamp;
 	struct client *client = e->client;
 	unsigned long flags;
 
@@ -581,6 +583,8 @@ static int init_request(struct client *client,
 			int destination_id, int speed)
 {
 	struct outbound_transaction_event *e;
+	struct fw_cdev_event_response *rsp;
+	void *payload;
 	int ret;
 
 	if (request->tcode != TCODE_STREAM_DATA &&
@@ -594,14 +598,14 @@ static int init_request(struct client *client,
 	e = kmalloc(sizeof(*e) + request->length, GFP_KERNEL);
 	if (e == NULL)
 		return -ENOMEM;
-
 	e->client = client;
-	e->response.length = request->length;
-	e->response.closure = request->closure;
 
-	if (request->data &&
-	    copy_from_user(e->response.data,
-			   u64_to_uptr(request->data), request->length)) {
+	rsp = &e->rsp.without_tstamp;
+	rsp->length = request->length;
+	rsp->closure = request->closure;
+	payload = rsp->data;
+
+	if (request->data && copy_from_user(payload, u64_to_uptr(request->data), request->length)) {
 		ret = -EFAULT;
 		goto failed;
 	}
@@ -611,10 +615,9 @@ static int init_request(struct client *client,
 	if (ret < 0)
 		goto failed;
 
-	fw_send_request(client->device->card, &e->r.transaction,
-			request->tcode, destination_id, request->generation,
-			speed, request->offset, e->response.data,
-			request->length, complete_transaction, e);
+	fw_send_request(client->device->card, &e->r.transaction, request->tcode, destination_id,
+			request->generation, speed, request->offset, payload, request->length,
+			complete_transaction, e);
 	return 0;
 
  failed: