Rework routing system

- Add 'route' to snd_avirt_stream, remove from audio path
- Add route checking - ensure that source ap and ink ap have
compatible hw params
- Add private data support for both source and sink Audio
Paths, to ensure that the PCM can hold multiple private data(s).
- Add ability to use copy_kernel and exttriggers from AVIRT instead of from Audio Paths
- Reintroduce pcm_trigger and pcm_prepare, so that 
they may be called appropriately from AVIRT, rather
than child Audio Paths.

Signed-off-by: Mark Farrugia <mark.farrugia@fiberdyne.com.au>

6 files changed, 490 insertions, 115 deletions

diff --git a/configfs.c b/configfs.c
index 5668cb3..bc10efb 100644
--- a/configfs.c
+++ b/configfs.c
@@ -68,6 +68,66 @@ CFG_SND_AVIRT_CHANNELS(stream);
 CFG_SND_AVIRT_DIRECTION_RO(route);
 CFG_SND_AVIRT_CHANNELS(route);
 
+/*
+ * Check PCM hw params between a source and a sink
+ */
+#define CHK_ROUTE_ERR(source_hw, sink_hw, field)                                \
+	do {                                                                    \
+		if (source_hw->field != sink_hw->field) {                       \
+			D_ERRORK(                                               \
+				"Route HW mismatch: ##field (src:%d, sink:%d)", \
+				source_hw->field, sink_hw->field);              \
+			return -1;                                              \
+		}                                                               \
+	} while (0)
+
+/*
+ * Check the a route's source and sink Audio Path's hardware params, to ensure
+ * compatibility
+ */
+static int cfg_snd_avirt_route_verify_hw(struct snd_avirt_audiopath *source_ap,
+					 struct snd_avirt_audiopath *sink_ap)
+{
+	const struct snd_pcm_hardware *source_hw = source_ap->hw;
+	const struct snd_pcm_hardware *sink_hw = sink_ap->hw;
+
+	CHK_ROUTE_ERR(source_hw, sink_hw, channels_max);
+	CHK_ROUTE_ERR(source_hw, sink_hw, channels_min);
+	CHK_ROUTE_ERR(source_hw, sink_hw, rate_max);
+	CHK_ROUTE_ERR(source_hw, sink_hw, rate_min);
+	CHK_ROUTE_ERR(source_hw, sink_hw, rates);
+
+	return 0;
+}
+
+/*
+ * Store the Audio Path endpoint (source or sink), and check compatiblity
+ */
+static int cfg_snd_avirt_route_ap_store(struct snd_avirt_route *route,
+					struct snd_avirt_audiopath *ap,
+					snd_avirt_route_endpoint endpoint)
+{
+	/* If other endpoint is set, we want to check that the two Audio Path
+	 * endpoints are compatible before we set this endpoint */
+	if (route->endpoint_ap[!endpoint]) {
+		if (!cfg_snd_avirt_route_verify_hw(
+			    route->endpoint_ap[!endpoint], ap)) {
+			route->endpoint_ap[endpoint] = ap;
+			D_INFOK("Route successfully created: '%s' [%s -> %s]",
+				route->uid, ap->uid,
+				route->endpoint_ap[!endpoint]->uid);
+			return 0;
+		} else {
+			D_ERRORK("Route could not be created: %s", route->uid);
+			return -1;
+		}
+	} else {
+		route->endpoint_ap[endpoint] = ap;
+	}
+
+	return 0;
+}
+
 static ssize_t cfg_snd_avirt_stream_map_show(struct config_item *item,
 					     char *page)
 {
@@ -98,85 +158,100 @@ static struct configfs_attribute *cfg_snd_avirt_stream_attrs[] = {
 	NULL,
 };
 
-static ssize_t cfg_snd_avirt_route_to_ap_show(struct config_item *item,
-					      char *page)
+static ssize_t cfg_snd_avirt_route_sink_ap_show(struct config_item *item,
+						char *page)
 {
 	struct snd_avirt_route *route = snd_avirt_route_from_config_item(item);
+	if (!route) {
+		D_ERRORK("Cannot get route!");
+		goto exit_err;
+	}
 
-	if (route)
-		if (route->to_ap)
-			return sprintf(page, "%s\n", route->to_ap->uid);
+	if (route->endpoint_ap[SND_AVIRT_ROUTE_SINK])
+		return sprintf(page, "%s\n",
+			       route->endpoint_ap[SND_AVIRT_ROUTE_SINK]->uid);
 
+exit_err:
 	return sprintf(page, "\n");
 }
 
-static ssize_t cfg_snd_avirt_route_to_ap_store(struct config_item *item,
-					       const char *page, size_t count)
+static ssize_t cfg_snd_avirt_route_sink_ap_store(struct config_item *item,
+						 const char *page, size_t count)
 {
 	char *uid_ap;
 	struct snd_avirt_route *route = snd_avirt_route_from_config_item(item);
-	struct snd_avirt_audiopath *to_ap;
+	struct snd_avirt_audiopath *sink_ap;
+
+	if (!route) {
+		D_ERRORK("Cannot get route!");
+		goto exit;
+	}
 
 	uid_ap = strsep((char **)&page, "\n");
-	to_ap = snd_avirt_audiopath_get(uid_ap);
-	if (!to_ap) {
+	sink_ap = snd_avirt_audiopath_get(uid_ap);
+	if (!sink_ap) {
 		D_ERRORK("Audio Path '%s' does not exist!", uid_ap);
-		D_ERRORK("Cannot set 'route'->'to_ap'");
-		return count;
+		D_ERRORK("Cannot set 'route'->'sink_ap'");
+		goto exit;
 	}
 
-	route->to_ap = to_ap;
-	if (route->from_ap) {
-		route->from_ap->route_to_ap = to_ap;
-		route->to_ap->route_from_ap = route->from_ap;
-	}
+	cfg_snd_avirt_route_ap_store(route, sink_ap, SND_AVIRT_ROUTE_SINK);
 
+exit:
 	return count;
 }
-CONFIGFS_ATTR(cfg_snd_avirt_route_, to_ap);
+CONFIGFS_ATTR(cfg_snd_avirt_route_, sink_ap);
 
-static ssize_t cfg_snd_avirt_route_from_ap_show(struct config_item *item,
-						char *page)
+static ssize_t cfg_snd_avirt_route_source_ap_show(struct config_item *item,
+						  char *page)
 {
 	struct snd_avirt_route *route = snd_avirt_route_from_config_item(item);
+	if (!route) {
+		D_ERRORK("Cannot get route!");
+		goto exit_err;
+	}
 
-	if (route)
-		if (route->from_ap)
-			return sprintf(page, "%s\n", route->from_ap->uid);
+	if (route->endpoint_ap[SND_AVIRT_ROUTE_SOURCE])
+		return sprintf(page, "%s\n",
+			       route->endpoint_ap[SND_AVIRT_ROUTE_SOURCE]->uid);
 
+exit_err:
 	return sprintf(page, "\n");
 }
 
-static ssize_t cfg_snd_avirt_route_from_ap_store(struct config_item *item,
-						 const char *page, size_t count)
+static ssize_t cfg_snd_avirt_route_source_ap_store(struct config_item *item,
+						   const char *page,
+						   size_t count)
 {
 	char *uid_ap;
 	struct snd_avirt_route *route = snd_avirt_route_from_config_item(item);
-	struct snd_avirt_audiopath *from_ap;
+	struct snd_avirt_audiopath *source_ap;
+
+	if (!route) {
+		D_ERRORK("Cannot get route!");
+		goto exit;
+	}
 
 	uid_ap = strsep((char **)&page, "\n");
-	from_ap = snd_avirt_audiopath_get(uid_ap);
-	if (!from_ap) {
+	source_ap = snd_avirt_audiopath_get(uid_ap);
+	if (!source_ap) {
 		D_ERRORK("Audio Path '%s' does not exist!", uid_ap);
-		D_ERRORK("Cannot set 'route'->'from_ap'");
+		D_ERRORK("Cannot set 'route'->'source_ap'");
 		return count;
 	}
 
-	route->from_ap = from_ap;
-	if (route->to_ap) {
-		route->to_ap->route_from_ap = from_ap;
-		route->from_ap->route_to_ap = route->to_ap;
-	}
+	cfg_snd_avirt_route_ap_store(route, source_ap, SND_AVIRT_ROUTE_SOURCE);
 
+exit:
 	return count;
 }
-CONFIGFS_ATTR(cfg_snd_avirt_route_, from_ap);
+CONFIGFS_ATTR(cfg_snd_avirt_route_, source_ap);
 
 static struct configfs_attribute *cfg_snd_avirt_route_attrs[] = {
 	&cfg_snd_avirt_route_attr_channels,
 	&cfg_snd_avirt_route_attr_direction,
-	&cfg_snd_avirt_route_attr_from_ap,
-	&cfg_snd_avirt_route_attr_to_ap,
+	&cfg_snd_avirt_route_attr_source_ap,
+	&cfg_snd_avirt_route_attr_sink_ap,
 	NULL,
 };
 
@@ -202,7 +277,7 @@ static void cfg_snd_avirt_route_release(struct config_item *item)
 		return;
 	}
 
-	D_INFOK("Release route: %s", route->name);
+	D_INFOK("Release route: %s", route->uid);
 	kfree(route);
 }
 
@@ -297,8 +372,6 @@ cfg_snd_avirt_route_make_item(struct config_group *group, const char *name)
 	config_item_init_type_name(&route->item, name,
 				   &cfg_snd_avirt_route_type);
 
-	D_INFOK("Make route: %s", route->name);
-
 	return &route->item;
 }
 
diff --git a/core.c b/core.c
index f7e7978..41d6b40 100644
--- a/core.c
+++ b/core.c
@@ -51,7 +51,7 @@ static void pcm_private_free(struct snd_pcm *pcm)
 	/* Free Audio Path private data */
 	avirt_private_data = (struct snd_avirt_private_data *)pcm->private_data;
 	if (avirt_private_data) {
-		if (avirt_private_data->ap_private_data &&
+		if (avirt_private_data->ap_private_data[0] &&
 		    avirt_private_data->ap_private_free)
 			avirt_private_data->ap_private_free(pcm);
 	}
@@ -94,7 +94,7 @@ static struct snd_pcm *snd_avirt_pcm_create(struct snd_avirt_stream *stream)
 		snd_pcm_set_ops(pcm, SNDRV_PCM_STREAM_CAPTURE, stream->pcm_ops);
 
 	pcm->info_flags = 0;
-	strcpy(pcm->name, stream->name);
+	strncpy(pcm->name, stream->name, MAX_NAME_LEN);
 
 	avirt_private_data = kzalloc(sizeof(*avirt_private_data), GFP_KERNEL);
 	pcm->private_data = avirt_private_data;
@@ -106,6 +106,22 @@ static struct snd_pcm *snd_avirt_pcm_create(struct snd_avirt_stream *stream)
 	return pcm;
 }
 
+static struct snd_avirt_route *snd_avirt_route_get(const char *uid)
+{
+	struct list_head *entry;
+	struct config_item *item;
+	struct snd_avirt_route *route;
+
+	list_for_each (entry, &core.route_group->cg_children) {
+		item = container_of(entry, struct config_item, ci_entry);
+		route = snd_avirt_route_from_config_item(item);
+		if (!strcmp(route->uid, uid))
+			return route;
+	}
+
+	return NULL;
+}
+
 int snd_avirt_stream_set_map(struct snd_avirt_stream *stream, const char *map)
 {
 	struct snd_avirt_audiopath *audiopath;
@@ -127,6 +143,10 @@ int snd_avirt_stream_set_map(struct snd_avirt_stream *stream, const char *map)
 		return -EFAULT;
 	}
 
+	/* Check for any routes that have been created for this stream */
+	stream->route = snd_avirt_route_get(stream->name);
+
+	/* Set up PCM ops */
 	if (!stream->direction)
 		pcm_ops_ap = (struct snd_pcm_ops *)audiopath->pcm_playback_ops;
 	else
@@ -140,8 +160,6 @@ int snd_avirt_stream_set_map(struct snd_avirt_stream *stream, const char *map)
 	}
 
 	/* Set PCM ops for the Audio Path*/
-	PCM_OPS_SET(pcm_ops_ap, &stream->pcm_ops, prepare);
-	PCM_OPS_SET(pcm_ops_ap, &stream->pcm_ops, trigger);
 	PCM_OPS_SET(pcm_ops_ap, &stream->pcm_ops, pointer);
 	PCM_OPS_SET(pcm_ops_ap, &stream->pcm_ops, get_time_info);
 	PCM_OPS_SET(pcm_ops_ap, &stream->pcm_ops, fill_silence);
@@ -185,9 +203,124 @@ static int snd_avirt_streams_get(const char *map,
 }
 
 /**
- * snd_avirt_audiopath_get - retrieves the Audio Path by its UID
- * @uid: Unique ID for the Audio Path
- * @return: Corresponding Audio Path
+ * snd_avirt_route_endpoint_pos - get route endpoint position for Audio Path
+ * @pcm: The PCM whose route to inspect.
+ * @ap_uid: The Audio Path UID to get
+ * @endpoint: The route position (SND_AVIRT_ROUTE_SOURCE or SND_AVIRT_ROUTE_SINK)
+ *            of the Audio Path in it's route (if any).
+ * @return: 0 if an Audio Path is found in the route, -1 if there is no route,
+ *          or -2 otherwise.
+ */
+int snd_avirt_route_endpoint_pos(struct snd_pcm *pcm, const char *ap_uid,
+				 snd_avirt_route_endpoint *endpoint)
+{
+	struct snd_avirt_audiopath *endpoint_ap;
+	struct snd_avirt_stream *stream;
+	int i;
+
+	stream = snd_avirt_stream_find_by_device(pcm->device);
+	if (IS_ERR_VALUE(stream) || !stream)
+		goto exit_err;
+
+	if (!stream->route)
+		return -1;
+
+	for (i = 0; i < 2; i++) {
+		endpoint_ap = stream->route->endpoint_ap[i];
+		if (endpoint_ap)
+			if (!strcmp(endpoint_ap->uid, ap_uid)) {
+				*endpoint = i;
+				return 0;
+			}
+	}
+
+exit_err:
+	D_ERRORK("Could not find Audio Path '%s' in route '%s'", ap_uid,
+		 stream->route->uid);
+	return -2;
+}
+
+/**
+ * snd_avirt_route_endpoint_copy - get endpoint copy function for a given
+ *                                 Audio Path's source/sink.
+ * @ap: The Audio Path whose endpoint copy function to find.
+ * @endpoint: The endpoint (SND_AVIRT_ROUTE_SOURCE or SND_AVIRT_ROUTE_SINK).
+ * @return: A snd_pcm_copy_kernel function pointer that can be used to either:
+ *          1. Source PCM data into the Audio Path, or,
+ *          2. Sink PCM data out of the Audio Path.
+ *          If no Audio Path endpoint is routed for 'endpoint', NULL is returned.
+ */
+snd_pcm_copy_kernel
+snd_avirt_route_endpoint_copy(struct snd_pcm_substream *substream,
+			      snd_avirt_route_endpoint endpoint)
+{
+	struct snd_avirt_audiopath *endpoint_ap;
+	struct snd_avirt_stream *stream;
+
+	if (endpoint < 0 || endpoint > 1) {
+		D_ERRORK("Route endpoint must be 0 or 1");
+		return NULL;
+	}
+
+	stream = snd_avirt_stream_find_by_device(substream->pcm->device);
+	if (IS_ERR_VALUE(stream) || !stream)
+		return NULL;
+
+	if (!stream->route)
+		return NULL;
+	endpoint_ap = stream->route->endpoint_ap[endpoint];
+	if (!endpoint_ap)
+		return NULL;
+
+	switch (endpoint) {
+	case SND_AVIRT_ROUTE_SOURCE:
+		return endpoint_ap->pcm_capture_ops->copy_kernel;
+	case SND_AVIRT_ROUTE_SINK:
+		return endpoint_ap->pcm_playback_ops->copy_kernel;
+	}
+
+	return NULL;
+}
+EXPORT_SYMBOL_GPL(snd_avirt_route_endpoint_copy);
+
+/**
+ * snd_avirt_route_endpoint_trigger - Trigger an Audio Path's endpoint
+ *                                    (sink/source).
+ * @uid: The Audio Path whose endpoint trigger function to call.
+ * @endpoint: The endpoint (SND_AVIRT_ROUTE_SOURCE or SND_AVIRT_ROUTE_SINK).
+ * @return: 0 on success or -1 on failure.
+ */
+int snd_avirt_route_endpoint_trigger(struct snd_pcm_substream *substream,
+				     snd_avirt_route_endpoint endpoint)
+{
+	struct snd_avirt_audiopath *endpoint_ap;
+	struct snd_avirt_stream *stream;
+
+	if (endpoint < 0 || endpoint > 1) {
+		D_ERRORK("Route endpoint must be 0 or 1");
+		return -1;
+	}
+
+	stream = snd_avirt_stream_find_by_device(substream->pcm->device);
+	if (IS_ERR_VALUE(stream) || !stream)
+		return -1;
+
+	if (!stream->route)
+		return -1;
+	endpoint_ap = stream->route->endpoint_ap[endpoint];
+	if (!endpoint_ap)
+		return -1;
+
+	endpoint_ap->pcm_exttrigger();
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(snd_avirt_route_endpoint_trigger);
+
+/**
+ * snd_avirt_audiopath_get - get Audio Path by it's UID
+ * @uid: The Audio Path UID to get
+ * @return: The Audio Path if it exists, NULL otherwise.
  */
 struct snd_avirt_audiopath *snd_avirt_audiopath_get(const char *uid)
 {
@@ -202,6 +335,62 @@ struct snd_avirt_audiopath *snd_avirt_audiopath_get(const char *uid)
 }
 EXPORT_SYMBOL_GPL(snd_avirt_audiopath_get);
 
+/*
+ * snd_avirt_audiopath_set_private_data - set PCM private data for an Audio Path
+ * @ap: The Audio Path whose private data to set.
+ * @pcm: The PCM where the private data is stored.
+ * @ap_private_data: The value to set to the private data.
+ * @return: 0 on success, -1 on failure.
+ */
+int snd_avirt_audiopath_set_private_data(struct snd_avirt_audiopath *ap,
+					 struct snd_pcm *pcm,
+					 void *ap_private_data)
+{
+	int err = 0;
+	snd_avirt_route_endpoint endpoint = SND_AVIRT_ROUTE_SOURCE;
+	struct snd_avirt_private_data *avirt_private_data = pcm->private_data;
+
+	err = snd_avirt_route_endpoint_pos(pcm, ap->uid, &endpoint);
+	if (err == -2)
+		goto exit_err;
+	if (!avirt_private_data)
+		goto exit_err;
+
+	avirt_private_data->ap_private_data[endpoint] = ap_private_data;
+
+	return 0;
+
+exit_err:
+	return -1;
+}
+EXPORT_SYMBOL_GPL(snd_avirt_audiopath_set_private_data);
+
+/*
+ * snd_avirt_audiopath_get_private_data - get PCM private data for an Audio Path
+ * @ap: The Audio Path whose private data to get.
+ * @pcm: The PCM where the private data is stored.
+ * @return: The value assigned to the private data.
+ */
+void *snd_avirt_audiopath_get_private_data(struct snd_avirt_audiopath *ap,
+					   struct snd_pcm *pcm)
+{
+	int err = 0;
+	snd_avirt_route_endpoint endpoint = SND_AVIRT_ROUTE_SOURCE;
+	struct snd_avirt_private_data *avirt_private_data = pcm->private_data;
+
+	err = snd_avirt_route_endpoint_pos(pcm, ap->uid, &endpoint);
+	if (err == -2)
+		goto exit_err;
+	if (!avirt_private_data)
+		goto exit_err;
+
+	return avirt_private_data->ap_private_data[endpoint];
+
+exit_err:
+	return NULL;
+}
+EXPORT_SYMBOL_GPL(snd_avirt_audiopath_get_private_data);
+
 /**
  * snd_avirt_audiopath_register - register Audio Path with AVIRT
  * @audiopath: Audio Path to be registered
@@ -271,12 +460,12 @@ EXPORT_SYMBOL_GPL(snd_avirt_audiopath_deregister);
 
 /**
  * snd_avirt_route_create - Create audio route
- * @name: The name designated to the audio route
+ * @uid: The unique ID designated to the audio route.
  * @direction: The PCM direction (SNDRV_PCM_STREAM_PLAYBACK or
  *             SNDRV_PCM_STREAM_CAPTURE)
  * @return: The newly created audio route if successful, or an error pointer
  */
-struct snd_avirt_route *snd_avirt_route_create(const char *name, int direction)
+struct snd_avirt_route *snd_avirt_route_create(const char *uid, int direction)
 {
 	struct snd_avirt_route *route;
 
@@ -284,7 +473,7 @@ struct snd_avirt_route *snd_avirt_route_create(const char *name, int direction)
 	if (!route)
 		return ERR_PTR(-ENOMEM);
 
-	strcpy(route->name, name);
+	strncpy(route->uid, uid, MAX_NAME_LEN);
 	route->channels = 0;
 	route->direction = direction;
 
@@ -312,8 +501,8 @@ struct snd_avirt_stream *snd_avirt_stream_create(const char *name,
 	if (!stream)
 		return ERR_PTR(-ENOMEM);
 
-	strcpy(stream->name, name);
-	strcpy(stream->map, "none");
+	strncpy(stream->name, name, MAX_NAME_LEN);
+	strncpy(stream->map, "none", MAX_NAME_LEN);
 	stream->channels = 0;
 	stream->direction = direction;
 	stream->device = core.stream_count++;
diff --git a/core.h b/core.h
index e4fb7a4..f915c04 100644
--- a/core.h
+++ b/core.h
@@ -128,6 +128,18 @@ struct snd_avirt_audiopath *snd_avirt_audiopath_get(const char *uid);
 struct snd_avirt_route *snd_avirt_route_create(const char *name, int direction);
 
 /**
+ * snd_avirt_route_endpoint_pos - get route endpoint position for Audio Path
+ * @pcm: The PCM whose route to inspect.
+ * @ap_uid: The Audio Path UID to get
+ * @endpoint: The route position (SND_AVIRT_ROUTE_SOURCE or SND_AVIRT_ROUTE_SINK)
+ *            of the Audio Path in it's route (if any).
+ * @return: 0 if an Audio Path is found in the route, -1 if there is no route,
+ *          or -2 otherwise.
+ */
+int snd_avirt_route_endpoint_pos(struct snd_pcm *pcm, const char *ap_uid,
+				 snd_avirt_route_endpoint *endpoint);
+
+/**
  * snd_avirt_stream_from_config_item - Convert config_item to a snd_avirt_stream
  * @item: The config_item to convert from
  * @return: The item's snd_avirt_stream if successful, NULL otherwise
diff --git a/pcm.c b/pcm.c
index fc01953..32456cd 100644
--- a/pcm.c
+++ b/pcm.c
@@ -15,20 +15,57 @@
 #define D_PRINTK(fmt, args...) DDEBUG(D_LOGNAME, fmt, ##args)
 #define D_ERRORK(fmt, args...) DERROR(D_LOGNAME, fmt, ##args)
 
+#define AUDIOPATH_PCM_CB(ap, cb, ops, substream, ...)                          \
+	(((ap)->ops->cb) ? (ap)->ops->cb((substream), ##__VA_ARGS__) : 0)
+
+#define DO_AUDIOPATH_PCM_ROUTE_CBS(ap, cb, ops, substream, ...)                \
+	({                                                                     \
+		int __err = 0, __endpoint = substream->stream;                 \
+		struct snd_avirt_stream *__stream =                            \
+			snd_avirt_stream_find_by_device(                       \
+				substream->pcm->device);                       \
+		if (!IS_ERR_VALUE(__stream) && __stream) {                     \
+			struct snd_avirt_audiopath *__endpoint_ap;             \
+			if (__stream->route) {                                 \
+				__endpoint_ap =                                \
+					__stream->route                        \
+						->endpoint_ap[__endpoint];     \
+				if ((__endpoint_ap)) {                         \
+					__err = AUDIOPATH_PCM_CB(              \
+						__endpoint_ap, cb, ops,        \
+						(substream), ##__VA_ARGS__);   \
+				}                                              \
+			}                                                      \
+		}                                                              \
+		(__err);                                                       \
+	})
 /**
- * DO_AUDIOPATH_CB - Used to call into an Audio Path's ALSA PCM callback from
- * AVIRT, where AVIRT's own callback must be attended to first.
+ * DO_AUDIOPATH_PCM_CBS - Call an Audio Path's ALSA PCM callbacks from AVIRT.
+ * If the Audio Path has routing enabled, then we call the appropriate
+ * from/to Audio Path's ALSA PCM callbacks
  */
-#define DO_AUDIOPATH_CB(ap, callback, substream, ...)                          \
-	((!substream->stream) ?                                                \
-		 (((ap)->pcm_playback_ops->callback) ?                         \
-			  (ap)->pcm_playback_ops->callback((substream),        \
-							   ##__VA_ARGS__) :    \
-			  0) :                                                 \
-		 (((ap)->pcm_capture_ops->callback) ?                          \
-			  (ap)->pcm_capture_ops->callback((substream),         \
-							  ##__VA_ARGS__) :     \
-			  0))
+#define DO_AUDIOPATH_PCM_CBS(ap, cb, substream, ...)                           \
+	({                                                                     \
+		int __err = 0;                                                 \
+		if (substream->stream) {                                       \
+			__err = AUDIOPATH_PCM_CB((ap), cb, pcm_capture_ops,    \
+						 (substream), ##__VA_ARGS__);  \
+			if (__err >= 0) {                                      \
+				__err = DO_AUDIOPATH_PCM_ROUTE_CBS(            \
+					(ap), cb, pcm_playback_ops,            \
+					(substream), ##__VA_ARGS__);           \
+			}                                                      \
+		} else {                                                       \
+			__err = AUDIOPATH_PCM_CB((ap), cb, pcm_playback_ops,   \
+						 (substream), ##__VA_ARGS__);  \
+			if (__err >= 0) {                                      \
+				__err = DO_AUDIOPATH_PCM_ROUTE_CBS(            \
+					(ap), cb, pcm_capture_ops,             \
+					(substream), ##__VA_ARGS__);           \
+			}                                                      \
+		}                                                              \
+		(__err);                                                       \
+	})
 
 #define PRIVATE_DATA(substream)                                                \
 	((struct snd_avirt_private_data *)substream->private_data)
@@ -82,8 +119,8 @@ static int pcm_open(struct snd_pcm_substream *substream)
 	hw->channels_min = chans;
 	hw->channels_max = chans;
 
-	// Do additional Audio Path 'open' callback
-	return DO_AUDIOPATH_CB(audiopath, open, substream);
+	// Do additional Audio Path 'open' callbacks
+	return DO_AUDIOPATH_PCM_CBS(audiopath, open, substream);
 }
 
 /**
@@ -97,12 +134,44 @@ static int pcm_open(struct snd_pcm_substream *substream)
 static int pcm_close(struct snd_pcm_substream *substream)
 {
 	// Do additional Audio Path 'close' callback
-	return DO_AUDIOPATH_CB(
+	return DO_AUDIOPATH_PCM_CBS(
 		(struct snd_avirt_audiopath *)PRIVATE_DATA(substream)->audiopath,
 		close, substream);
 }
 
 /**
+ * pcm_close - Implements 'close' callback for PCM middle layer
+ * @substream: pointer to ALSA PCM substream
+ *
+ * This is called when a PCM substream is closed.
+ *
+ * Returns 0 on success or error code otherwise.
+ */
+static int pcm_trigger(struct snd_pcm_substream *substream, int cmd)
+{
+	// Do additional Audio Path 'trigger' callback
+	return DO_AUDIOPATH_PCM_CBS(
+		(struct snd_avirt_audiopath *)PRIVATE_DATA(substream)->audiopath,
+		trigger, substream, cmd);
+}
+
+/**
+ * pcm_close - Implements 'close' callback for PCM middle layer
+ * @substream: pointer to ALSA PCM substream
+ *
+ * This is called when a PCM substream is closed.
+ *
+ * Returns 0 on success or error code otherwise.
+ */
+static int pcm_prepare(struct snd_pcm_substream *substream)
+{
+	// Do additional Audio Path 'prepare' callback
+	return DO_AUDIOPATH_PCM_CBS(
+		(struct snd_avirt_audiopath *)PRIVATE_DATA(substream)->audiopath,
+		prepare, substream);
+}
+
+/**
  * pcm_hw_params - Implements 'hw_params' callback for PCM middle layer
  * @substream: pointer to ALSA PCM substream
  * @hw_params: contains the hardware parameters for the PCM
@@ -149,7 +218,7 @@ static int pcm_hw_free(struct snd_pcm_substream *substream)
 	int err;
 
 	// Do additional Audio Path 'hw_free' callback
-	err = DO_AUDIOPATH_CB(
+	err = DO_AUDIOPATH_PCM_CBS(
 		(struct snd_avirt_audiopath *)PRIVATE_DATA(substream)->audiopath,
 		hw_free, substream);
 	if (err < 0)
@@ -165,6 +234,8 @@ static int pcm_hw_free(struct snd_pcm_substream *substream)
 struct snd_pcm_ops pcm_ops_avirt = {
 	.open = pcm_open,
 	.close = pcm_close,
+	.prepare = pcm_prepare,
+	.trigger = pcm_trigger,
 	.ioctl = snd_pcm_lib_ioctl,
 	.hw_params = pcm_hw_params,
 	.hw_free = pcm_hw_free,
diff --git a/sound/avirt.h b/sound/avirt.h
index 8378004..ecb0a21 100644
--- a/sound/avirt.h
+++ b/sound/avirt.h
@@ -39,6 +39,34 @@ typedef int (*snd_avirt_audiopath_configure)(
 typedef void (*snd_avirt_pcm_exttrigger)(void);
 
 /**
+ * ALSA copy_kernel function type
+ * A standard PCM operation from ALSA. This is used in AVIRT to copy PCM data
+ * between Audio Paths, along given routes.
+ */
+typedef int (*snd_pcm_copy_kernel)(struct snd_pcm_substream *substream,
+				   int channel, unsigned long pos, void *buf,
+				   unsigned long bytes);
+
+/*
+ * AVIRT route source/sink enumeration types
+ */
+typedef enum snd_avirt_route_endpoint_t {
+	SND_AVIRT_ROUTE_SOURCE,
+	SND_AVIRT_ROUTE_SINK,
+} snd_avirt_route_endpoint;
+
+/**
+ * Audio routing
+ */
+struct snd_avirt_route {
+	char uid[MAX_NAME_LEN]; /* Unique identifier */
+	unsigned int channels; /* Route stream channel count */
+	unsigned int direction; /* Route stream direction */
+	struct snd_avirt_audiopath *endpoint_ap[2]; /* Source/sink */
+	struct config_item item; /* configfs item reference */
+};
+
+/**
  * AVIRT Audio Path info
  */
 typedef struct snd_avirt_audiopath snd_avirt_audiopath;
@@ -50,24 +78,8 @@ struct snd_avirt_audiopath {
 	const struct snd_pcm_ops *pcm_playback_ops; /* ALSA PCM playback ops */
 	const struct snd_pcm_ops *pcm_capture_ops; /* ALSA PCM capture ops */
 	snd_avirt_audiopath_configure configure; /* Config callback function */
-	snd_avirt_pcm_exttrigger pcm_exttrigger;
+	snd_avirt_pcm_exttrigger pcm_exttrigger; /* External trigger callback */
 	void *context;
-
-	// MUST be at the end
-	struct snd_avirt_audiopath *route_from_ap;
-	struct snd_avirt_audiopath *route_to_ap;
-};
-
-/**
- * Audio routing
- */
-struct snd_avirt_route {
-	char name[MAX_NAME_LEN];
-	unsigned int channels;
-	unsigned int direction;
-	struct snd_avirt_audiopath *from_ap;
-	struct snd_avirt_audiopath *to_ap;
-	struct config_item item;
 };
 
 /**
@@ -81,6 +93,7 @@ struct snd_avirt_stream {
 	unsigned int direction; /* Stream direction */
 	struct snd_pcm *pcm; /* ALSA PCM  */
 	struct snd_pcm_ops *pcm_ops; /* ALSA PCM ops */
+	struct snd_avirt_route *route; /* Associated route, if any */
 	struct config_item item; /* configfs item reference */
 };
 
@@ -101,9 +114,10 @@ typedef void (*snd_avirt_ap_private_free)(struct snd_pcm *pcm);
  * Private Data Expansion
  */
 struct snd_avirt_private_data {
+	/* Initial Audio Path in the route */
 	struct snd_avirt_audiopath *audiopath;
-	void *ap_private_data;
-
+	/* Private data for source/sink Audio Paths */
+	void *ap_private_data[2];
 	snd_avirt_ap_private_free ap_private_free;
 };
 
@@ -128,4 +142,48 @@ int snd_avirt_audiopath_deregister(struct snd_avirt_audiopath *audiopath);
  */
 struct snd_avirt_audiopath *snd_avirt_audiopath_get(const char *uid);
 
+/*
+ * snd_avirt_audiopath_set_private_data - set PCM private data for an Audio Path
+ * @ap: The Audio Path whose private data to set.
+ * @pcm: The PCM where the private data is stored.
+ * @ap_private_data: The value to set to the private data.
+ * @return: 0 on success, -1 on failure.
+ */
+int snd_avirt_audiopath_set_private_data(struct snd_avirt_audiopath *ap,
+					 struct snd_pcm *pcm,
+					 void *ap_private_data);
+
+/*
+ * snd_avirt_audiopath_get_private_data - get PCM private data for an Audio Path
+ * @ap: The Audio Path whose private data to get.
+ * @pcm: The PCM where the private data is stored.
+ * @return: The value assigned to the private data.
+ */
+void *snd_avirt_audiopath_get_private_data(struct snd_avirt_audiopath *ap,
+					   struct snd_pcm *pcm);
+
+/**
+ * snd_avirt_route_endpoint_copy - get endpoint copy function for a given
+ *                                 Audio Path's source/sink.
+ * @ap: The Audio Path whose endpoint copy function to find.
+ * @endpoint: The endpoint (SND_AVIRT_ROUTE_SOURCE or SND_AVIRT_ROUTE_SINK).
+ * @return: A snd_pcm_copy_kernel function pointer that can be used to either:
+ *          1. Source PCM data into the Audio Path, or,
+ *          2. Sink PCM data out of the Audio Path.
+ *          If no Audio Path endpoint is routed for 'endpoint', NULL is returned.
+ */
+snd_pcm_copy_kernel
+snd_avirt_route_endpoint_copy(struct snd_pcm_substream *substream,
+			      snd_avirt_route_endpoint endpoint);
+
+/**
+ * snd_avirt_route_endpoint_trigger - Trigger an Audio Path's endpoint
+ *                                    (sink/source).
+ * @uid: The Audio Path whose endpoint trigger function to call.
+ * @endpoint: The endpoint (SND_AVIRT_ROUTE_SOURCE or SND_AVIRT_ROUTE_SINK).
+ * @return: 0 on success or -1 on failure.
+ */
+int snd_avirt_route_endpoint_trigger(struct snd_pcm_substream *substream,
+				     snd_avirt_route_endpoint endpoint);
+
 #endif // __SOUND_AVIRT_H
diff --git a/sysfs.c b/sysfs.c
index 29f9b5d..23132ce 100644
--- a/sysfs.c
+++ b/sysfs.c
@@ -115,42 +115,14 @@ static ssize_t version_show(struct snd_avirt_audiopath_obj *audiopath_obj,
 		       audiopath->version[1], audiopath->version[2]);
 }
 
-static ssize_t route_from_ap_show(struct snd_avirt_audiopath_obj *audiopath_obj,
-				  struct snd_avirt_audiopath_attribute *attr,
-				  char *buf)
-{
-	struct snd_avirt_audiopath *audiopath = audiopath_obj->path;
-
-	if (audiopath->route_from_ap)
-		return sprintf(buf, "%s\n", audiopath->route_from_ap->uid);
-
-	return 0;
-}
-
-static ssize_t route_to_ap_show(struct snd_avirt_audiopath_obj *audiopath_obj,
-				struct snd_avirt_audiopath_attribute *attr,
-				char *buf)
-{
-	struct snd_avirt_audiopath *audiopath = audiopath_obj->path;
-
-	if (audiopath->route_to_ap)
-		return sprintf(buf, "%s\n", audiopath->route_to_ap->uid);
-
-	return 0;
-}
-
 static struct snd_avirt_audiopath_attribute snd_avirt_audiopath_attrs[] = {
 	__ATTR_RO(name),
 	__ATTR_RO(version),
-	__ATTR_RO(route_from_ap),
-	__ATTR_RO(route_to_ap),
 };
 
 static struct attribute *snd_avirt_audiopath_def_attrs[] = {
 	&snd_avirt_audiopath_attrs[0].attr,
 	&snd_avirt_audiopath_attrs[1].attr,
-	&snd_avirt_audiopath_attrs[2].attr,
-	&snd_avirt_audiopath_attrs[3].attr,
 	NULL,
 };