alsa-mixer: Pick at most one fallback mapping

The old behaviour was such that if none of the normal mappings worked,
we would probe ALL fallbacks. I don't think that makes sense, and it
caused concrete issues: let's say we have a regular stereo mic device,
but there's no "front" PCM defined for it. In this situation we would
probe the stereo-fallback mapping (which uses "hw" instead of "front"),
and it would work, but then we'd also probe the "multichannel-input"
mapping, which would also work, so we end up with two mappings that
don't have any difference in behaviour.

I think it's better to simply pick the first working fallback and ignore
the rest.

Fixes: https://gitlab.freedesktop.org/pulseaudio/pulseaudio/-/issues/901
(issue is marked as confidential due to unreleased hardware)

Part-of: <https://gitlab.freedesktop.org/pulseaudio/pulseaudio/-/merge_requests/304>

diff --git a/src/modules/alsa/alsa-mixer.c b/src/modules/alsa/alsa-mixer.c
index c406297..8b9ccfb 100644 (file)
--- a/src/modules/alsa/alsa-mixer.c
+++ b/src/modules/alsa/alsa-mixer.c
@@ -5155,14 +5155,14 @@ void pa_alsa_profile_set_probe(
         if (p->output_mappings)
             PA_IDXSET_FOREACH(m, p->output_mappings, idx)
                 if (m->output_pcm) {
-                    found_output |= !p->fallback_output;
+                    found_output = true;
                     mapping_paths_probe(m, p, PA_ALSA_DIRECTION_OUTPUT, used_paths, mixers);
                 }
 
         if (p->input_mappings)
             PA_IDXSET_FOREACH(m, p->input_mappings, idx)
                 if (m->input_pcm) {
-                    found_input |= !p->fallback_input;
+                    found_input = true;
                     mapping_paths_probe(m, p, PA_ALSA_DIRECTION_INPUT, used_paths, mixers);
                 }
     }