[PATCH v2 1/2] ASoC: dapm: support user-defined stop condition in dai_get_connected_widgets

[PATCH v2 1/2] ASoC: dapm: support user-defined stop condition in dai_get_connected_widgets

[Piotr Stankiewicz]

Certain situations may warrant examining DAPM paths only to a certain
arbitrary point, as opposed to always following them to the end. For
instance, when establishing a connection between a front-end DAI link
and a back-end DAI link in a DPCM path, it does not make sense to walk
the DAPM graph beyond the first widget associated with a back-end link.

This patch introduces a mechanism which lets a user of
dai_get_connected_widgets supply a function which will be called for
every node during the graph walk. When invoked, this function can
execute arbitrary logic to decide whether the walk, given a DAPM widget
and walk direction, should be terminated at that point or continued
as normal.

Signed-off-by: Piotr Stankiewicz <piotrs@opensource.wolfsonmicro.com>
---
 include/sound/soc-dapm.h |    5 +++-
 sound/soc/soc-dapm.c     |   68 +++++++++++++++++++++++++++++++++++++---------
 sound/soc/soc-pcm.c      |    3 +-
 3 files changed, 61 insertions(+), 15 deletions(-)

diff --git a/include/sound/soc-dapm.h b/include/sound/soc-dapm.h
index 9706946..fe5bc93 100644
--- a/include/sound/soc-dapm.h
+++ b/include/sound/soc-dapm.h
@@ -357,6 +357,7 @@ struct snd_soc_dapm_context;
 struct regulator;
 struct snd_soc_dapm_widget_list;
 struct snd_soc_dapm_update;
+enum snd_soc_dapm_direction;
 
 int dapm_regulator_event(struct snd_soc_dapm_widget *w,
 			 struct snd_kcontrol *kcontrol, int event);
@@ -450,7 +451,9 @@ void dapm_mark_endpoints_dirty(struct snd_soc_card *card);
 
 /* dapm path query */
 int snd_soc_dapm_dai_get_connected_widgets(struct snd_soc_dai *dai, int stream,
-	struct snd_soc_dapm_widget_list **list);
+	struct snd_soc_dapm_widget_list **list,
+	int (*custom_stop_condition)(struct snd_soc_dapm_widget *,
+				     enum snd_soc_dapm_direction));
 
 struct snd_soc_dapm_context *snd_soc_dapm_kcontrol_dapm(
 	struct snd_kcontrol *kcontrol);
diff --git a/sound/soc/soc-dapm.c b/sound/soc/soc-dapm.c
index 801ae1a..075f0d7 100644
--- a/sound/soc/soc-dapm.c
+++ b/sound/soc/soc-dapm.c
@@ -1073,7 +1073,11 @@ static int dapm_widget_list_create(struct snd_soc_dapm_widget_list **list,
  */
 static __always_inline int is_connected_ep(struct snd_soc_dapm_widget *widget,
 	struct list_head *list, enum snd_soc_dapm_direction dir,
-	int (*fn)(struct snd_soc_dapm_widget *, struct list_head *))
+	int (*fn)(struct snd_soc_dapm_widget *, struct list_head *,
+		  int (*custom_stop_condition)(struct snd_soc_dapm_widget *,
+					       enum snd_soc_dapm_direction)),
+	int (*custom_stop_condition)(struct snd_soc_dapm_widget *,
+				     enum snd_soc_dapm_direction))
 {
 	enum snd_soc_dapm_direction rdir = SND_SOC_DAPM_DIR_REVERSE(dir);
 	struct snd_soc_dapm_path *path;
@@ -1088,6 +1092,13 @@ static __always_inline int is_connected_ep(struct snd_soc_dapm_widget *widget,
 	if (list)
 		list_add_tail(&widget->work_list, list);
 
+	if (custom_stop_condition) {
+		con = custom_stop_condition(widget, dir);
+		if (con >= 0)
+			return con;
+		con = 0;
+	}
+
 	if ((widget->is_ep & SND_SOC_DAPM_DIR_TO_EP(dir)) && widget->connected) {
 		widget->endpoints[dir] = snd_soc_dapm_suspend_check(widget);
 		return widget->endpoints[dir];
@@ -1106,7 +1117,7 @@ static __always_inline int is_connected_ep(struct snd_soc_dapm_widget *widget,
 
 		if (path->connect) {
 			path->walking = 1;
-			con += fn(path->node[dir], list);
+			con += fn(path->node[dir], list, custom_stop_condition);
 			path->walking = 0;
 		}
 	}
@@ -1119,23 +1130,41 @@ static __always_inline int is_connected_ep(struct snd_soc_dapm_widget *widget,
 /*
  * Recursively check for a completed path to an active or physically connected
  * output widget. Returns number of complete paths.
+ *
+ * Optionally, can be supplied with a function acting as a stopping condition.
+ * This function takes the dapm widget currently being examined and the walk
+ * direction as an arguments, and should return an integer, as follows:
+ * - >=0: if the walk is to be stopped (this should indicate the number of
+ *        endpoints the widget has),
+ * - <0 : if the walk is to be continued as normal.
  */
 static int is_connected_output_ep(struct snd_soc_dapm_widget *widget,
-	struct list_head *list)
+	struct list_head *list,
+	int (*custom_stop_condition)(struct snd_soc_dapm_widget *i,
+				     enum snd_soc_dapm_direction))
 {
 	return is_connected_ep(widget, list, SND_SOC_DAPM_DIR_OUT,
-			is_connected_output_ep);
+			is_connected_output_ep, custom_stop_condition);
 }
 
 /*
  * Recursively check for a completed path to an active or physically connected
  * input widget. Returns number of complete paths.
+ *
+ * Optionally, can be supplied with a function acting as a stopping condition.
+ * This function takes the dapm widget currently being examined and the walk
+ * direction as an arguments, and should return an integer, as follows:
+ * - >=0: if the walk is to be stopped (this should indicate the number of
+ *        endpoints the widget has),
+ * - <0 : if the walk is to be continued as normal.
  */
 static int is_connected_input_ep(struct snd_soc_dapm_widget *widget,
-	struct list_head *list)
+	struct list_head *list,
+	int (*custom_stop_condition)(struct snd_soc_dapm_widget *i,
+				     enum snd_soc_dapm_direction))
 {
 	return is_connected_ep(widget, list, SND_SOC_DAPM_DIR_IN,
-			is_connected_input_ep);
+			is_connected_input_ep, custom_stop_condition);
 }
 
 /**
@@ -1143,15 +1172,26 @@ static int is_connected_input_ep(struct snd_soc_dapm_widget *widget,
  * @dai: the soc DAI.
  * @stream: stream direction.
  * @list: list of active widgets for this stream.
+ * @custom_stop_condition: (optional) a function meant to stop the widget graph
+ *                         walk based on custom logic.
  *
  * Queries DAPM graph as to whether an valid audio stream path exists for
  * the initial stream specified by name. This takes into account
  * current mixer and mux kcontrol settings. Creates list of valid widgets.
  *
+ * Optionally, can be supplied with a function acting as a stopping condition.
+ * This function takes the dapm widget currently being examined and the walk
+ * direction as an arguments, and should return an integer, as follows:
+ * - >=0: if the walk is to be stopped (this should indicate the number of
+ *        endpoints the widget has),
+ * - <0 : if the walk is to be continued as normal.
+ *
  * Returns the number of valid paths or negative error.
  */
 int snd_soc_dapm_dai_get_connected_widgets(struct snd_soc_dai *dai, int stream,
-	struct snd_soc_dapm_widget_list **list)
+	struct snd_soc_dapm_widget_list **list,
+	int (*custom_stop_condition)(struct snd_soc_dapm_widget *,
+				     enum snd_soc_dapm_direction))
 {
 	struct snd_soc_card *card = dai->component->card;
 	struct snd_soc_dapm_widget *w;
@@ -1171,9 +1211,11 @@ int snd_soc_dapm_dai_get_connected_widgets(struct snd_soc_dai *dai, int stream,
 	}
 
 	if (stream == SNDRV_PCM_STREAM_PLAYBACK)
-		paths = is_connected_output_ep(dai->playback_widget, &widgets);
+		paths = is_connected_output_ep(dai->playback_widget, &widgets,
+				custom_stop_condition);
 	else
-		paths = is_connected_input_ep(dai->capture_widget, &widgets);
+		paths = is_connected_input_ep(dai->capture_widget, &widgets,
+				custom_stop_condition);
 
 	/* Drop starting point */
 	list_del(widgets.next);
@@ -1268,8 +1310,8 @@ static int dapm_generic_check_power(struct snd_soc_dapm_widget *w)
 
 	DAPM_UPDATE_STAT(w, power_checks);
 
-	in = is_connected_input_ep(w, NULL);
-	out = is_connected_output_ep(w, NULL);
+	in = is_connected_input_ep(w, NULL, NULL);
+	out = is_connected_output_ep(w, NULL, NULL);
 	return out != 0 && in != 0;
 }
 
@@ -1928,8 +1970,8 @@ static ssize_t dapm_widget_power_read_file(struct file *file,
 		in = 0;
 		out = 0;
 	} else {
-		in = is_connected_input_ep(w, NULL);
-		out = is_connected_output_ep(w, NULL);
+		in = is_connected_input_ep(w, NULL, NULL);
+		out = is_connected_output_ep(w, NULL, NULL);
 	}
 
 	ret = snprintf(buf, PAGE_SIZE, "%s: %s%s  in %d out %d",
diff --git a/sound/soc/soc-pcm.c b/sound/soc/soc-pcm.c
index aa99dac..c2b0aa8 100644
--- a/sound/soc/soc-pcm.c
+++ b/sound/soc/soc-pcm.c
@@ -1294,7 +1294,8 @@ int dpcm_path_get(struct snd_soc_pcm_runtime *fe,
 	int paths;
 
 	/* get number of valid DAI paths and their widgets */
-	paths = snd_soc_dapm_dai_get_connected_widgets(cpu_dai, stream, list);
+	paths = snd_soc_dapm_dai_get_connected_widgets(cpu_dai, stream, list,
+			NULL);
 
 	dev_dbg(fe->dev, "ASoC: found %d audio %s paths\n", paths,
 			stream ? "capture" : "playback");
-- 
1.7.10.4

[PATCH v2 2/2] ASoC: dpcm: play nice with CODEC<->CODEC links

[Piotr Stankiewicz]

Currently in situations where a normal CODEC to CODEC link follows a
DPCM DAI, an error in the following form will be logged:

ASoC: can't get [playback|capture] BE for <widget name>
ASoC: no BE found for <widget name>

This happens because all widgets in a path containing a DPCM DAI will
be passed to dpcm_add_paths, which will try to interpret the CODEC<->CODEC
as if it were a DPCM DAI, in turn causing the error.

This patch aims to resolve the described issue by stopping the DPCM graph
walk, initiated from dpcm_path_get, at the first widget associated with
a DPCM BE.

Signed-off-by: Piotr Stankiewicz <piotrs@opensource.wolfsonmicro.com>
---
 sound/soc/soc-pcm.c |   42 +++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 41 insertions(+), 1 deletion(-)

diff --git a/sound/soc/soc-pcm.c b/sound/soc/soc-pcm.c
index c2b0aa8..f29e518 100644
--- a/sound/soc/soc-pcm.c
+++ b/sound/soc/soc-pcm.c
@@ -1287,6 +1287,46 @@ static int widget_in_list(struct snd_soc_dapm_widget_list *list,
 	return 0;
 }
 
+static int dpcm_end_walk_at_be(struct snd_soc_dapm_widget *widget,
+		enum snd_soc_dapm_direction dir)
+{
+	struct snd_soc_card *card = widget->dapm->card;
+	struct snd_soc_pcm_runtime *rtd;
+	int i;
+
+	if (dir == SND_SOC_DAPM_DIR_OUT) {
+		list_for_each_entry(rtd, &card->rtd_list, list) {
+			if (!rtd->dai_link->no_pcm)
+				continue;
+
+			if (rtd->cpu_dai->playback_widget == widget)
+				return 0;
+
+			for (i = 0; i < rtd->num_codecs; ++i) {
+				struct snd_soc_dai *dai = rtd->codec_dais[i];
+				if (dai->playback_widget == widget)
+					return 0;
+			}
+		}
+	} else { /* SND_SOC_DAPM_DIR_IN */
+		list_for_each_entry(rtd, &card->rtd_list, list) {
+			if (!rtd->dai_link->no_pcm)
+				continue;
+
+			if (rtd->cpu_dai->capture_widget == widget)
+				return 0;
+
+			for (i = 0; i < rtd->num_codecs; ++i) {
+				struct snd_soc_dai *dai = rtd->codec_dais[i];
+				if (dai->capture_widget == widget)
+					return 0;
+			}
+		}
+	}
+
+	return -1;
+}
+
 int dpcm_path_get(struct snd_soc_pcm_runtime *fe,
 	int stream, struct snd_soc_dapm_widget_list **list)
 {
@@ -1295,7 +1335,7 @@ int dpcm_path_get(struct snd_soc_pcm_runtime *fe,
 
 	/* get number of valid DAI paths and their widgets */
 	paths = snd_soc_dapm_dai_get_connected_widgets(cpu_dai, stream, list,
-			NULL);
+			dpcm_end_walk_at_be);
 
 	dev_dbg(fe->dev, "ASoC: found %d audio %s paths\n", paths,
 			stream ? "capture" : "playback");
-- 
1.7.10.4

Re: [PATCH v2 1/2] ASoC: dapm: support user-defined stop condition in dai_get_connected_widgets

[Mark Brown]

[-- Attachment #1.1: Type: text/plain, Size: 856 bytes --]

On Thu, Apr 14, 2016 at 02:03:18PM +0100, Piotr Stankiewicz wrote:

> + * Optionally, can be supplied with a function acting as a stopping condition.
> + * This function takes the dapm widget currently being examined and the walk
> + * direction as an arguments, and should return an integer, as follows:
> + * - >=0: if the walk is to be stopped (this should indicate the number of
> + *        endpoints the widget has),
> + * - <0 : if the walk is to be continued as normal.

This seems really weird and uncomfortable.  From the naming I would
expect it to be a boolean function and I'm struggling to understand when
it would be useful to report multiple endpoints on a widget (edge
widgets normally being single objects).  The whole counting thing is
mainly a combination of debugging and an artefact of the implementation.
What's the motivation here?

[-- Attachment #1.2: signature.asc --]
[-- Type: application/pgp-signature, Size: 473 bytes --]

[-- Attachment #2: Type: text/plain, Size: 0 bytes --]

Re: [PATCH v2 1/2] ASoC: dapm: support user-defined stop condition in dai_get_connected_widgets

[Piotr Stankiewicz]

On Fri, May 13, 2016 at 01:09:05PM +0100, Mark Brown wrote:
> On Thu, Apr 14, 2016 at 02:03:18PM +0100, Piotr Stankiewicz wrote:
> 
> > + * Optionally, can be supplied with a function acting as a stopping condition.
> > + * This function takes the dapm widget currently being examined and the walk
> > + * direction as an arguments, and should return an integer, as follows:
> > + * - >=0: if the walk is to be stopped (this should indicate the number of
> > + *        endpoints the widget has),
> > + * - <0 : if the walk is to be continued as normal.
> 
> This seems really weird and uncomfortable.  From the naming I would
> expect it to be a boolean function and I'm struggling to understand when
> it would be useful to report multiple endpoints on a widget (edge
> widgets normally being single objects).  The whole counting thing is
> mainly a combination of debugging and an artefact of the implementation.
> What's the motivation here?

I don't have a strong reason for this. My motivation here was - since I
am adding support for stopping an arbitrary point, it could be that
someone would find a use in stopping the graph walk part-way through, and
still reporting the number of endpoints as normal. But, if that's
unlikely to be of use, I'm happy to make it a boolean function.

Re: [PATCH v2 1/2] ASoC: dapm: support user-defined stop condition in dai_get_connected_widgets

[Mark Brown]

[-- Attachment #1.1: Type: text/plain, Size: 983 bytes --]

On Fri, May 13, 2016 at 02:01:43PM +0100, Piotr Stankiewicz wrote:
> On Fri, May 13, 2016 at 01:09:05PM +0100, Mark Brown wrote:

> > This seems really weird and uncomfortable.  From the naming I would
> > expect it to be a boolean function and I'm struggling to understand when
> > it would be useful to report multiple endpoints on a widget (edge
> > widgets normally being single objects).  The whole counting thing is
> > mainly a combination of debugging and an artefact of the implementation.
> > What's the motivation here?

> I don't have a strong reason for this. My motivation here was - since I
> am adding support for stopping an arbitrary point, it could be that
> someone would find a use in stopping the graph walk part-way through, and
> still reporting the number of endpoints as normal. But, if that's
> unlikely to be of use, I'm happy to make it a boolean function.

Why would the number of endpoints at the edge of the graph ever be
something other than 0 or 1?

[-- Attachment #1.2: signature.asc --]
[-- Type: application/pgp-signature, Size: 473 bytes --]

[-- Attachment #2: Type: text/plain, Size: 0 bytes --]

Re: [PATCH v2 1/2] ASoC: dapm: support user-defined stop condition in dai_get_connected_widgets

[Piotr Stankiewicz]

On Fri, May 13, 2016 at 02:43:20PM +0100, Mark Brown wrote:
> On Fri, May 13, 2016 at 02:01:43PM +0100, Piotr Stankiewicz wrote:
> > On Fri, May 13, 2016 at 01:09:05PM +0100, Mark Brown wrote:
> 
> > > This seems really weird and uncomfortable.  From the naming I would
> > > expect it to be a boolean function and I'm struggling to understand when
> > > it would be useful to report multiple endpoints on a widget (edge
> > > widgets normally being single objects).  The whole counting thing is
> > > mainly a combination of debugging and an artefact of the implementation.
> > > What's the motivation here?
> 
> > I don't have a strong reason for this. My motivation here was - since I
> > am adding support for stopping an arbitrary point, it could be that
> > someone would find a use in stopping the graph walk part-way through, and
> > still reporting the number of endpoints as normal. But, if that's
> > unlikely to be of use, I'm happy to make it a boolean function.
> 
> Why would the number of endpoints at the edge of the graph ever be
> something other than 0 or 1?

Now that I think about it, indeed it does not make sense. I'll respin my
pathes with custom_stop_condition returning a bool.

[PATCH v2 1/2] ASoC: dapm: support user-defined stop condition in dai_get_connected_widgets

[Piotr Stankiewicz]

Certain situations may warrant examining DAPM paths only to a certain
arbitrary point, as opposed to always following them to the end. For
instance, when establishing a connection between a front-end DAI link
and a back-end DAI link in a DPCM path, it does not make sense to walk
the DAPM graph beyond the first widget associated with a back-end link.

This patch introduces a mechanism which lets a user of
dai_get_connected_widgets supply a function which will be called for
every node during the graph walk. When invoked, this function can
execute arbitrary logic to decide whether the walk, given a DAPM widget
and walk direction, should be terminated at that point or continued
as normal.

Signed-off-by: Piotr Stankiewicz <piotrs@opensource.wolfsonmicro.com>
---
 include/sound/soc-dapm.h |    5 +++-
 sound/soc/soc-dapm.c     |   68 +++++++++++++++++++++++++++++++++++++---------
 sound/soc/soc-pcm.c      |    3 +-
 3 files changed, 61 insertions(+), 15 deletions(-)

diff --git a/include/sound/soc-dapm.h b/include/sound/soc-dapm.h
index 9706946..fe5bc93 100644
--- a/include/sound/soc-dapm.h
+++ b/include/sound/soc-dapm.h
@@ -357,6 +357,7 @@ struct snd_soc_dapm_context;
 struct regulator;
 struct snd_soc_dapm_widget_list;
 struct snd_soc_dapm_update;
+enum snd_soc_dapm_direction;
 
 int dapm_regulator_event(struct snd_soc_dapm_widget *w,
 			 struct snd_kcontrol *kcontrol, int event);
@@ -450,7 +451,9 @@ void dapm_mark_endpoints_dirty(struct snd_soc_card *card);
 
 /* dapm path query */
 int snd_soc_dapm_dai_get_connected_widgets(struct snd_soc_dai *dai, int stream,
-	struct snd_soc_dapm_widget_list **list);
+	struct snd_soc_dapm_widget_list **list,
+	int (*custom_stop_condition)(struct snd_soc_dapm_widget *,
+				     enum snd_soc_dapm_direction));
 
 struct snd_soc_dapm_context *snd_soc_dapm_kcontrol_dapm(
 	struct snd_kcontrol *kcontrol);
diff --git a/sound/soc/soc-dapm.c b/sound/soc/soc-dapm.c
index 801ae1a..075f0d7 100644
--- a/sound/soc/soc-dapm.c
+++ b/sound/soc/soc-dapm.c
@@ -1073,7 +1073,11 @@ static int dapm_widget_list_create(struct snd_soc_dapm_widget_list **list,
  */
 static __always_inline int is_connected_ep(struct snd_soc_dapm_widget *widget,
 	struct list_head *list, enum snd_soc_dapm_direction dir,
-	int (*fn)(struct snd_soc_dapm_widget *, struct list_head *))
+	int (*fn)(struct snd_soc_dapm_widget *, struct list_head *,
+		  int (*custom_stop_condition)(struct snd_soc_dapm_widget *,
+					       enum snd_soc_dapm_direction)),
+	int (*custom_stop_condition)(struct snd_soc_dapm_widget *,
+				     enum snd_soc_dapm_direction))
 {
 	enum snd_soc_dapm_direction rdir = SND_SOC_DAPM_DIR_REVERSE(dir);
 	struct snd_soc_dapm_path *path;
@@ -1088,6 +1092,13 @@ static __always_inline int is_connected_ep(struct snd_soc_dapm_widget *widget,
 	if (list)
 		list_add_tail(&widget->work_list, list);
 
+	if (custom_stop_condition) {
+		con = custom_stop_condition(widget, dir);
+		if (con >= 0)
+			return con;
+		con = 0;
+	}
+
 	if ((widget->is_ep & SND_SOC_DAPM_DIR_TO_EP(dir)) && widget->connected) {
 		widget->endpoints[dir] = snd_soc_dapm_suspend_check(widget);
 		return widget->endpoints[dir];
@@ -1106,7 +1117,7 @@ static __always_inline int is_connected_ep(struct snd_soc_dapm_widget *widget,
 
 		if (path->connect) {
 			path->walking = 1;
-			con += fn(path->node[dir], list);
+			con += fn(path->node[dir], list, custom_stop_condition);
 			path->walking = 0;
 		}
 	}
@@ -1119,23 +1130,41 @@ static __always_inline int is_connected_ep(struct snd_soc_dapm_widget *widget,
 /*
  * Recursively check for a completed path to an active or physically connected
  * output widget. Returns number of complete paths.
+ *
+ * Optionally, can be supplied with a function acting as a stopping condition.
+ * This function takes the dapm widget currently being examined and the walk
+ * direction as an arguments, and should return an integer, as follows:
+ * - >=0: if the walk is to be stopped (this should indicate the number of
+ *        endpoints the widget has),
+ * - <0 : if the walk is to be continued as normal.
  */
 static int is_connected_output_ep(struct snd_soc_dapm_widget *widget,
-	struct list_head *list)
+	struct list_head *list,
+	int (*custom_stop_condition)(struct snd_soc_dapm_widget *i,
+				     enum snd_soc_dapm_direction))
 {
 	return is_connected_ep(widget, list, SND_SOC_DAPM_DIR_OUT,
-			is_connected_output_ep);
+			is_connected_output_ep, custom_stop_condition);
 }
 
 /*
  * Recursively check for a completed path to an active or physically connected
  * input widget. Returns number of complete paths.
+ *
+ * Optionally, can be supplied with a function acting as a stopping condition.
+ * This function takes the dapm widget currently being examined and the walk
+ * direction as an arguments, and should return an integer, as follows:
+ * - >=0: if the walk is to be stopped (this should indicate the number of
+ *        endpoints the widget has),
+ * - <0 : if the walk is to be continued as normal.
  */
 static int is_connected_input_ep(struct snd_soc_dapm_widget *widget,
-	struct list_head *list)
+	struct list_head *list,
+	int (*custom_stop_condition)(struct snd_soc_dapm_widget *i,
+				     enum snd_soc_dapm_direction))
 {
 	return is_connected_ep(widget, list, SND_SOC_DAPM_DIR_IN,
-			is_connected_input_ep);
+			is_connected_input_ep, custom_stop_condition);
 }
 
 /**
@@ -1143,15 +1172,26 @@ static int is_connected_input_ep(struct snd_soc_dapm_widget *widget,
  * @dai: the soc DAI.
  * @stream: stream direction.
  * @list: list of active widgets for this stream.
+ * @custom_stop_condition: (optional) a function meant to stop the widget graph
+ *                         walk based on custom logic.
  *
  * Queries DAPM graph as to whether an valid audio stream path exists for
  * the initial stream specified by name. This takes into account
  * current mixer and mux kcontrol settings. Creates list of valid widgets.
  *
+ * Optionally, can be supplied with a function acting as a stopping condition.
+ * This function takes the dapm widget currently being examined and the walk
+ * direction as an arguments, and should return an integer, as follows:
+ * - >=0: if the walk is to be stopped (this should indicate the number of
+ *        endpoints the widget has),
+ * - <0 : if the walk is to be continued as normal.
+ *
  * Returns the number of valid paths or negative error.
  */
 int snd_soc_dapm_dai_get_connected_widgets(struct snd_soc_dai *dai, int stream,
-	struct snd_soc_dapm_widget_list **list)
+	struct snd_soc_dapm_widget_list **list,
+	int (*custom_stop_condition)(struct snd_soc_dapm_widget *,
+				     enum snd_soc_dapm_direction))
 {
 	struct snd_soc_card *card = dai->component->card;
 	struct snd_soc_dapm_widget *w;
@@ -1171,9 +1211,11 @@ int snd_soc_dapm_dai_get_connected_widgets(struct snd_soc_dai *dai, int stream,
 	}
 
 	if (stream == SNDRV_PCM_STREAM_PLAYBACK)
-		paths = is_connected_output_ep(dai->playback_widget, &widgets);
+		paths = is_connected_output_ep(dai->playback_widget, &widgets,
+				custom_stop_condition);
 	else
-		paths = is_connected_input_ep(dai->capture_widget, &widgets);
+		paths = is_connected_input_ep(dai->capture_widget, &widgets,
+				custom_stop_condition);
 
 	/* Drop starting point */
 	list_del(widgets.next);
@@ -1268,8 +1310,8 @@ static int dapm_generic_check_power(struct snd_soc_dapm_widget *w)
 
 	DAPM_UPDATE_STAT(w, power_checks);
 
-	in = is_connected_input_ep(w, NULL);
-	out = is_connected_output_ep(w, NULL);
+	in = is_connected_input_ep(w, NULL, NULL);
+	out = is_connected_output_ep(w, NULL, NULL);
 	return out != 0 && in != 0;
 }
 
@@ -1928,8 +1970,8 @@ static ssize_t dapm_widget_power_read_file(struct file *file,
 		in = 0;
 		out = 0;
 	} else {
-		in = is_connected_input_ep(w, NULL);
-		out = is_connected_output_ep(w, NULL);
+		in = is_connected_input_ep(w, NULL, NULL);
+		out = is_connected_output_ep(w, NULL, NULL);
 	}
 
 	ret = snprintf(buf, PAGE_SIZE, "%s: %s%s  in %d out %d",
diff --git a/sound/soc/soc-pcm.c b/sound/soc/soc-pcm.c
index aa99dac..c2b0aa8 100644
--- a/sound/soc/soc-pcm.c
+++ b/sound/soc/soc-pcm.c
@@ -1294,7 +1294,8 @@ int dpcm_path_get(struct snd_soc_pcm_runtime *fe,
 	int paths;
 
 	/* get number of valid DAI paths and their widgets */
-	paths = snd_soc_dapm_dai_get_connected_widgets(cpu_dai, stream, list);
+	paths = snd_soc_dapm_dai_get_connected_widgets(cpu_dai, stream, list,
+			NULL);
 
 	dev_dbg(fe->dev, "ASoC: found %d audio %s paths\n", paths,
 			stream ? "capture" : "playback");
-- 
1.7.10.4