alsa: mixer - use safe dB range values when the override mask is unset

Use safe values for the min_dB and max_dB fields when the position mask
is unset to avoid breakage for the upper levels.

If the range is incorrect, the volume range shown in pavucontrol shows
strange values.

(Thanks to Wim Taymans for the idea.)

Signed-off-by: Jaroslav Kysela <perex@perex.cz>
Part-of: <https://gitlab.freedesktop.org/pulseaudio/pulseaudio/-/merge_requests/389>

diff --git a/src/modules/alsa/alsa-mixer.c b/src/modules/alsa/alsa-mixer.c
index 8b9ccfb..3a29132 100644 (file)
--- a/src/modules/alsa/alsa-mixer.c
+++ b/src/modules/alsa/alsa-mixer.c
@@ -3072,6 +3072,7 @@ int pa_alsa_path_probe(pa_alsa_path *p, pa_alsa_mapping *mapping, snd_mixer_t *m
     double min_dB[PA_CHANNEL_POSITION_MAX], max_dB[PA_CHANNEL_POSITION_MAX];
     pa_channel_position_t t;
     pa_channel_position_mask_t path_volume_channels = 0;
+    bool min_dB_set, max_dB_set;
     char buf[64];
 
     pa_assert(p);
@@ -3102,7 +3103,7 @@ int pa_alsa_path_probe(pa_alsa_path *p, pa_alsa_mapping *mapping, snd_mixer_t *m
             pa_log_debug("Probe of element %s failed.", buf);
             return -1;
         }
-        pa_log_debug("Probe of element %s succeeded (volume=%d, switch=%d, enumeration=%d).", buf, e->volume_use, e->switch_use, e->enumeration_use);
+        pa_log_debug("Probe of element %s succeeded (volume=%d, switch=%d, enumeration=%d, has_dB=%d).", buf, e->volume_use, e->switch_use, e->enumeration_use, e->has_dB);
 
         if (ignore_dB)
             e->has_dB = false;
@@ -3166,18 +3167,30 @@ int pa_alsa_path_probe(pa_alsa_path *p, pa_alsa_mapping *mapping, snd_mixer_t *m
     p->supported = true;
 
     p->min_dB = INFINITY;
+    min_dB_set = false;
     p->max_dB = -INFINITY;
+    max_dB_set = false;
 
     for (t = 0; t < PA_CHANNEL_POSITION_MAX; t++) {
         if (path_volume_channels & PA_CHANNEL_POSITION_MASK(t)) {
-            if (p->min_dB > min_dB[t])
+            if (p->min_dB > min_dB[t]) {
                 p->min_dB = min_dB[t];
+                min_dB_set = true;
+            }
 
-            if (p->max_dB < max_dB[t])
+            if (p->max_dB < max_dB[t]) {
                 p->max_dB = max_dB[t];
+                max_dB_set = true;
+            }
         }
     }
 
+    /* this is probably a wrong prediction, but it should be safe */
+    if (!min_dB_set)
+        p->min_dB = -INFINITY;
+    if (!max_dB_set)
+        p->max_dB = 0;
+
     return 0;
 }