ALSA: USB-audio: Break out creation of silent urbs from prepare_outbound_urb()

Refactoring in preparation for adding Zoom R16/24 quirk.
No functional change.
Signed-off-by: NRicard Wanderlof <ricardw@axis.com>
Signed-off-by: NTakashi Iwai <tiwai@suse.de>

sound/usb/endpoint.c

@@ -183,25 +183,13 @@ static void retire_inbound_urb(struct snd_usb_endpoint *ep,
 		ep->retire_data_urb(ep->data_subs, urb);
 }
 
-/*
- * Prepare a PLAYBACK urb for submission to the bus.
- */
-static void prepare_outbound_urb(struct snd_usb_endpoint *ep,
+static void prepare_silent_urb(struct snd_usb_endpoint *ep,
 			       struct snd_urb_ctx *ctx)
 {
-	int i;
 	struct urb *urb = ctx->urb;
-	unsigned char *cp = urb->transfer_buffer;
-
-	urb->dev = ep->chip->dev; /* we need to set this at each time */
-
-	switch (ep->type) {
-	case SND_USB_ENDPOINT_TYPE_DATA:
-		if (ep->prepare_data_urb) {
-			ep->prepare_data_urb(ep->data_subs, urb);
-		} else {
-			/* no data provider, so send silence */
 	unsigned int offs = 0;
+	int i;
+
 	for (i = 0; i < ctx->packets; ++i) {
 		int counts;
 
@@ -219,6 +207,26 @@ static void prepare_outbound_urb(struct snd_usb_endpoint *ep,
 	urb->transfer_buffer_length = offs * ep->stride;
 	memset(urb->transfer_buffer, ep->silence_value,
 	       offs * ep->stride);
+}
+
+/*
+ * Prepare a PLAYBACK urb for submission to the bus.
+ */
+static void prepare_outbound_urb(struct snd_usb_endpoint *ep,
+				 struct snd_urb_ctx *ctx)
+{
+	struct urb *urb = ctx->urb;
+	unsigned char *cp = urb->transfer_buffer;
+
+	urb->dev = ep->chip->dev; /* we need to set this at each time */
+
+	switch (ep->type) {
+	case SND_USB_ENDPOINT_TYPE_DATA:
+		if (ep->prepare_data_urb) {
+			ep->prepare_data_urb(ep->data_subs, urb);
+		} else {
+			/* no data provider, so send silence */
+			prepare_silent_urb(ep, ctx);
 		}
 		break;