ALSA: pcm: oss: Simplify plugin frame size calculations

Both snd_pcm_plug_client_size() and snd_pcm_plug_slave_size() do the
almost same calculations of calling src_frames() and dst_frames() in
the chain, but just to the different directions with each other.

This patch simplifies those functions.  Now they return -EINVAL for
the invalid direction, but practically seen, there is no functional
changes at all.

Link: https://lore.kernel.org/r/20200309185855.15693-1-tiwai@suse.deSigned-off-by: Takashi Iwai <tiwai@suse.de>

sound/core/oss/pcm_plugin.c

@@ -196,82 +196,74 @@ int snd_pcm_plugin_free(struct snd_pcm_plugin *plugin)
 	return 0;
 }
 
-snd_pcm_sframes_t snd_pcm_plug_client_size(struct snd_pcm_substream *plug, snd_pcm_uframes_t drv_frames)
+static snd_pcm_sframes_t calc_dst_frames(struct snd_pcm_substream *plug,
+					 snd_pcm_sframes_t frames)
 {
-	struct snd_pcm_plugin *plugin, *plugin_prev, *plugin_next;
-	int stream;
+	struct snd_pcm_plugin *plugin, *plugin_next;
 
-	if (snd_BUG_ON(!plug))
-		return -ENXIO;
-	if (drv_frames == 0)
-		return 0;
-	stream = snd_pcm_plug_stream(plug);
-	if (stream == SNDRV_PCM_STREAM_PLAYBACK) {
-		plugin = snd_pcm_plug_last(plug);
-		while (plugin && drv_frames > 0) {
-			if (drv_frames > plugin->buf_frames)
-				drv_frames = plugin->buf_frames;
-			plugin_prev = plugin->prev;
-			if (plugin->src_frames)
-				drv_frames = plugin->src_frames(plugin, drv_frames);
-			plugin = plugin_prev;
+	plugin = snd_pcm_plug_first(plug);
+	while (plugin && frames > 0) {
+		plugin_next = plugin->next;
+		if (plugin->dst_frames) {
+			frames = plugin->dst_frames(plugin, frames);
+			if (frames < 0)
+				return frames;
 		}
-	} else if (stream == SNDRV_PCM_STREAM_CAPTURE) {
-		plugin = snd_pcm_plug_first(plug);
-		while (plugin && drv_frames > 0) {
-			plugin_next = plugin->next;
-			if (plugin->dst_frames)
-				drv_frames = plugin->dst_frames(plugin, drv_frames);
-			if (drv_frames > plugin->buf_frames)
-				drv_frames = plugin->buf_frames;
-			plugin = plugin_next;
+		if (frames > plugin->buf_frames)
+			frames = plugin->buf_frames;
+		plugin = plugin_next;
+	}
+	return frames;
+}
+
+static snd_pcm_sframes_t calc_src_frames(struct snd_pcm_substream *plug,
+					 snd_pcm_sframes_t frames)
+{
+	struct snd_pcm_plugin *plugin, *plugin_prev;
+
+	plugin = snd_pcm_plug_last(plug);
+	while (plugin && frames > 0) {
+		if (frames > plugin->buf_frames)
+			frames = plugin->buf_frames;
+		plugin_prev = plugin->prev;
+		if (plugin->src_frames) {
+			frames = plugin->src_frames(plugin, frames);
+			if (frames < 0)
+				return frames;
 		}
-	} else
+		plugin = plugin_prev;
+	}
+	return frames;
+}
+
+snd_pcm_sframes_t snd_pcm_plug_client_size(struct snd_pcm_substream *plug, snd_pcm_uframes_t drv_frames)
+{
+	if (snd_BUG_ON(!plug))
+		return -ENXIO;
+	switch (snd_pcm_plug_stream(plug)) {
+	case SNDRV_PCM_STREAM_PLAYBACK:
+		return calc_src_frames(plug, drv_frames);
+	case SNDRV_PCM_STREAM_CAPTURE:
+		return calc_dst_frames(plug, drv_frames);
+	default:
 		snd_BUG();
-	return drv_frames;
+		return -EINVAL;
+	}
 }
 
 snd_pcm_sframes_t snd_pcm_plug_slave_size(struct snd_pcm_substream *plug, snd_pcm_uframes_t clt_frames)
 {
-	struct snd_pcm_plugin *plugin, *plugin_prev, *plugin_next;
-	snd_pcm_sframes_t frames;
-	int stream;
-	
 	if (snd_BUG_ON(!plug))
 		return -ENXIO;
-	if (clt_frames == 0)
-		return 0;
-	frames = clt_frames;
-	stream = snd_pcm_plug_stream(plug);
-	if (stream == SNDRV_PCM_STREAM_PLAYBACK) {
-		plugin = snd_pcm_plug_first(plug);
-		while (plugin && frames > 0) {
-			plugin_next = plugin->next;
-			if (plugin->dst_frames) {
-				frames = plugin->dst_frames(plugin, frames);
-				if (frames < 0)
-					return frames;
-			}
-			if (frames > plugin->buf_frames)
-				frames = plugin->buf_frames;
-			plugin = plugin_next;
-		}
-	} else if (stream == SNDRV_PCM_STREAM_CAPTURE) {
-		plugin = snd_pcm_plug_last(plug);
-		while (plugin) {
-			if (frames > plugin->buf_frames)
-				frames = plugin->buf_frames;
-			plugin_prev = plugin->prev;
-			if (plugin->src_frames) {
-				frames = plugin->src_frames(plugin, frames);
-				if (frames < 0)
-					return frames;
-			}
-			plugin = plugin_prev;
-		}
-	} else
+	switch (snd_pcm_plug_stream(plug)) {
+	case SNDRV_PCM_STREAM_PLAYBACK:
+		return calc_dst_frames(plug, clt_frames);
+	case SNDRV_PCM_STREAM_CAPTURE:
+		return calc_src_frames(plug, clt_frames);
+	default:
 		snd_BUG();
-	return frames;
+		return -EINVAL;
+	}
 }
 
 static int snd_pcm_plug_formats(const struct snd_mask *mask,