alsa-ucm: Make combination port names deterministic

At the moment, port names combined from multiple devices are generated
based on the order that the devices are specified in config. This makes
programmatic use of thsee ports a bit painful, so let's make them be
combined in alphabetical order.

diff --git a/src/modules/alsa/alsa-ucm.c b/src/modules/alsa/alsa-ucm.c
index 9eb6412b5e4a2ee9470d661d33a32b28824d3f83..47ff926e2d1646b70ddde6296009779432967062 100644 (file)
--- a/src/modules/alsa/alsa-ucm.c
+++ b/src/modules/alsa/alsa-ucm.c
@@ -664,6 +664,13 @@ int pa_alsa_ucm_get_verb(snd_use_case_mgr_t *uc_mgr, const char *verb_name, cons
     return 0;
 }
 
+static int pa_alsa_ucm_device_cmp(const void *a, const void *b) {
+    const pa_alsa_ucm_device *d1 = *(pa_alsa_ucm_device **)a;
+    const pa_alsa_ucm_device *d2 = *(pa_alsa_ucm_device **)b;
+
+    return strcmp(pa_proplist_gets(d1->proplist, PA_ALSA_PROP_UCM_NAME), pa_proplist_gets(d2->proplist, PA_ALSA_PROP_UCM_NAME));
+}
+
 static void ucm_add_port_combination(
         pa_hashmap *hash,
         pa_alsa_ucm_mapping_context *context,
@@ -681,9 +688,16 @@ static void ucm_add_port_combination(
     char *name, *desc;
     const char *dev_name;
     const char *direction;
-    pa_alsa_ucm_device *dev;
+    pa_alsa_ucm_device *sorted[num], *dev;
+
+    for (i = 0; i < num; i++)
+        sorted[i] = pdevices[i];
+
+    /* Sort by alphabetical order so as to have a deterministic naming scheme
+     * for combination ports */
+    qsort(&sorted[0], num, sizeof(pa_alsa_ucm_device *), pa_alsa_ucm_device_cmp);
 
-    dev = pdevices[0];
+    dev = sorted[0];
     dev_name = pa_proplist_gets(dev->proplist, PA_ALSA_PROP_UCM_NAME);
 
     name = pa_sprintf_malloc("%s%s", is_sink ? PA_UCM_PRE_TAG_OUTPUT : PA_UCM_PRE_TAG_INPUT, dev_name);
@@ -696,7 +710,7 @@ static void ucm_add_port_combination(
     for (i = 1; i < num; i++) {
         char *tmp;
 
-        dev = pdevices[i];
+        dev = sorted[i];
         dev_name = pa_proplist_gets(dev->proplist, PA_ALSA_PROP_UCM_NAME);
 
         tmp = pa_sprintf_malloc("%s+%s", name, dev_name);