ASoC: dapm: support user-defined stop condition in dai_get_connected_widgets

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>
Signed-off-by: Mark Brown <broonie@kernel.org>

3 files changed, 51 insertions, 15 deletions

diff --git a/include/sound/soc-dapm.h b/include/sound/soc-dapm.h
index 3101d53468aa..ca77db443499 100644
--- a/include/sound/soc-dapm.h
+++ b/include/sound/soc-dapm.h
@@ -358,6 +358,7 @@ 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);
@@ -451,7 +452,9 @@ 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,
+        bool (*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 c4464858bf01..db781f6faaec 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 *,
+                  bool (*custom_stop_condition)(struct snd_soc_dapm_widget *,
+                                                enum snd_soc_dapm_direction)),
+        bool (*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 +1092,9 @@ 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 && custom_stop_condition(widget, dir))
+                return con;
+
         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 +1113,7 @@ 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 +1126,37 @@ 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, it should return true if the walk should be
+ * stopped and false otherwise.
  */
 static int is_connected_output_ep(struct snd_soc_dapm_widget *widget,
-        struct list_head *list)
+        struct list_head *list,
+        bool (*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, it should return true if the walk should be
+ * stopped and false otherwise.
  */
 static int is_connected_input_ep(struct snd_soc_dapm_widget *widget,
-        struct list_head *list)
+        struct list_head *list,
+        bool (*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 +1164,24 @@ 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, it should return true if the walk should be
+ * stopped and false otherwise.
+ *
  * 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,
+        bool (*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 +1201,11 @@ 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 +1300,8 @@ 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 +1960,8 @@ 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 aa99dac31b3b..c2b0aa82f3f1 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");