ALSA: usb-audio: Unify the code for the next packet size calculation

There are two places calculating the next packet size for the playback
stream in the exactly same way.  Provide the single helper for this
purpose and use it from both places gracefully.
Tested-by: Keith Milner <kamilner@superlative.org>
Tested-by: Dylan Robinson <dylan_robinson@motu.com>
Link: https://lore.kernel.org/r/20201123085347.19667-32-tiwai@suse.deSigned-off-by: Takashi Iwai <tiwai@suse.de>

sound/usb/endpoint.c

@@ -121,13 +121,13 @@ int snd_usb_endpoint_implicit_feedback_sink(struct snd_usb_endpoint *ep)
 }
 
 /*
- * For streaming based on information derived from sync endpoints,
- * prepare_outbound_urb_sizes() will call slave_next_packet_size() to
- * determine the number of samples to be sent in the next packet.
+ * Return the number of samples to be sent in the next packet
+ * for streaming based on information derived from sync endpoints
  *
- * For implicit feedback, slave_next_packet_size() is unused.
+ * This won't be used for implicit feedback which takes the packet size
+ * returned from the sync source
  */
-int snd_usb_endpoint_slave_next_packet_size(struct snd_usb_endpoint *ep)
+static int slave_next_packet_size(struct snd_usb_endpoint *ep)
 {
 	unsigned long flags;
 	int ret;
@@ -145,11 +145,10 @@ int snd_usb_endpoint_slave_next_packet_size(struct snd_usb_endpoint *ep)
 }
 
 /*
- * For adaptive and synchronous endpoints, prepare_outbound_urb_sizes()
- * will call next_packet_size() to determine the number of samples to be
- * sent in the next packet.
+ * Return the number of samples to be sent in the next packet
+ * for adaptive and synchronous endpoints
  */
-int snd_usb_endpoint_next_packet_size(struct snd_usb_endpoint *ep)
+static int next_packet_size(struct snd_usb_endpoint *ep)
 {
 	int ret;
 
@@ -167,6 +166,21 @@ int snd_usb_endpoint_next_packet_size(struct snd_usb_endpoint *ep)
 	return ret;
 }
 
+/*
+ * snd_usb_endpoint_next_packet_size: Return the number of samples to be sent
+ * in the next packet
+ */
+int snd_usb_endpoint_next_packet_size(struct snd_usb_endpoint *ep,
+				      struct snd_urb_ctx *ctx, int idx)
+{
+	if (ctx->packet_size[idx])
+		return ctx->packet_size[idx];
+	else if (ep->sync_master)
+		return slave_next_packet_size(ep);
+	else
+		return next_packet_size(ep);
+}
+
 static void call_retire_callback(struct snd_usb_endpoint *ep,
 				 struct urb *urb)
 {
@@ -223,13 +237,7 @@ static void prepare_silent_urb(struct snd_usb_endpoint *ep,
 		unsigned int length;
 		int counts;
 
-		if (ctx->packet_size[i])
-			counts = ctx->packet_size[i];
-		else if (ep->sync_master)
-			counts = snd_usb_endpoint_slave_next_packet_size(ep);
-		else
-			counts = snd_usb_endpoint_next_packet_size(ep);
-
+		counts = snd_usb_endpoint_next_packet_size(ep, ctx, i);
 		length = counts * ep->stride; /* number of silent bytes */
 		offset = offs * ep->stride + extra * i;
 		urb->iso_frame_desc[i].offset = offset;

sound/usb/endpoint.h

@@ -45,7 +45,7 @@ void snd_usb_endpoint_release(struct snd_usb_endpoint *ep);
 void snd_usb_endpoint_free(struct snd_usb_endpoint *ep);
 
 int snd_usb_endpoint_implicit_feedback_sink(struct snd_usb_endpoint *ep);
-int snd_usb_endpoint_slave_next_packet_size(struct snd_usb_endpoint *ep);
-int snd_usb_endpoint_next_packet_size(struct snd_usb_endpoint *ep);
+int snd_usb_endpoint_next_packet_size(struct snd_usb_endpoint *ep,
+				      struct snd_urb_ctx *ctx, int idx);
 
 #endif /* __USBAUDIO_ENDPOINT_H */

sound/usb/pcm.c

@@ -1512,13 +1512,7 @@ static void prepare_playback_urb(struct snd_usb_substream *subs,
 	spin_lock_irqsave(&subs->lock, flags);
 	subs->frame_limit += ep->max_urb_frames;
 	for (i = 0; i < ctx->packets; i++) {
-		if (ctx->packet_size[i])
-			counts = ctx->packet_size[i];
-		else if (ep->sync_master)
-			counts = snd_usb_endpoint_slave_next_packet_size(ep);
-		else
-			counts = snd_usb_endpoint_next_packet_size(ep);
-
+		counts = snd_usb_endpoint_next_packet_size(ep, ctx, i);
 		/* set up descriptor */
 		urb->iso_frame_desc[i].offset = frames * ep->stride;
 		urb->iso_frame_desc[i].length = counts * ep->stride;