[pulseaudio-discuss] [PATCH 4/4] alsa-mixer: Attempt to detect and then drop redundant paths in the path set.

[Colin Guthrie]

In order to try and avoid 'spamming' the user with port choices,
attempt to detect and remove any redundant paths in a path set.

This should solve a problem case with some USB Headsets which result in
two paths both using the 'Speaker' element when no 'Master' element exists
(and even in this case, one of those two paths wouldn't really work
anyway due to not actually having h/w volume control due to the absense
of 'Master')
---
 src/modules/alsa/alsa-mixer.c |   46 +++++++++++++++++++++++++++++++++++++++++
 1 files changed, 46 insertions(+), 0 deletions(-)

diff --git a/src/modules/alsa/alsa-mixer.c b/src/modules/alsa/alsa-mixer.c
index abd3bf2..ea5a49d 100644
--- a/src/modules/alsa/alsa-mixer.c
+++ b/src/modules/alsa/alsa-mixer.c
@@ -2873,6 +2873,51 @@ void pa_alsa_path_set_dump(pa_alsa_path_set *ps) {
         pa_alsa_path_dump(p);
 }
 
+static void path_set_condense(pa_alsa_path_set *ps) {
+    pa_alsa_path *p1, *np1, *p2, *np2;
+
+    for (p1 = ps->paths; p1; p1 = np1) {
+        np1 = p1->next;
+
+        for (p2 = p1->next; p2; p2 = np2) {
+            pa_alsa_element *e1, *e2;
+            pa_bool_t same = TRUE;
+
+            np2 = p2->next;
+
+            /* Compare the elements of each set... */
+            pa_assert_se(e1 = p1->elements);
+            pa_assert_se(e2 = p2->elements);
+
+            while (same) {
+                if (pa_streq(e1->alsa_name, e2->alsa_name) && e1->switch_use == e2->switch_use) {
+                    e1 = e1->next;
+                    e2 = e2->next;
+                    if ((e1 && !e2) || (!e1 && e2))
+                        same = FALSE;
+                    else if (!e1 && !e2)
+                        break;
+                } else
+                    same = FALSE;
+            }
+
+            if (same) {
+                pa_alsa_path *remove_path, *keep_path;
+                if (p1->priority >= p2->priority) {
+                    keep_path = p1;
+                    remove_path = p2;
+                } else {
+                    keep_path = p2;
+                    remove_path = p1;
+                }
+                pa_log_debug("Removing redundant path '%s' as it contains the same elements as '%s' which has higher priority.", remove_path->name, keep_path->name);
+                PA_LLIST_REMOVE(pa_alsa_path, ps->paths, remove_path);
+                pa_alsa_path_free(remove_path);
+            }
+        }
+    }
+}
+
 static void path_set_make_paths_unique(pa_alsa_path_set *ps) {
     pa_alsa_path *p, *q;
 
@@ -2928,6 +2973,7 @@ void pa_alsa_path_set_probe(pa_alsa_path_set *ps, snd_mixer_t *m, pa_bool_t igno
         }
     }
 
+    path_set_condense(ps);
     path_set_make_paths_unique(ps);
     ps->probed = TRUE;
 }
-- 
1.7.6