Bug#859017: pulseaudio: switch-on-port-available picks unavailable device port

[Vivek Das Mohapatra]

Package: pulseaudio
Version: 5.0-13
Severity: normal

Dear Maintainer,

    * What led up to the situation?

      Volume/Mute state was not restored on a laptop on reboot:
      The speaker was always muted.

    * What exactly did you do (or not do) that was effective (or
      ineffective)?

      Set the volume (in either gdm or gnome), rebooted (either from
      within the gnome session or after logging out).

    * What was the outcome of this action?

      Sound (speaker) was always muted on reboot.

    * What outcome did you expect instead?

      Volume should have been restored to the value recorded
      in the pulseaudio .tdb files.

Eventually tracked this down to the wrong device port being selected by
module-switch-on-port-available - the helper function new_sink_source
iterates over the device ports and picks the one with the highest priority
but then, just before returning, does this:

     if (p->available != PA_AVAILABLE_NO)
         return NULL;

ie the selected port is returned _only_ if it is NOT available.

This logic error appears to be in pulseaudio 10.x (the stretch version)
also.

This is used by (for example):

   static pa_hook_result_t sink_new_hook_callback(pa_core *c, pa_sink_new_data *new_data, void *u) {

       pa_device_port *p = new_sink_source(new_data->ports, new_data->active_port);

       if (p) {
           pa_log_debug("Switching initial port for sink '%s' to '%s'", new_data->name, p->name);
           pa_sink_new_data_set_port(new_data, p->name);
       }
       return PA_HOOK_OK;
   }

So this module will never choose an available port.

The p->available != PA_AVAILABLE_NO pattern appears all over the place in
this module but I _think_ this is the only place where it's used the
wrong way round.

The following fixed the symptom here (and the pa -vvvv log indicated that
a more sensible set of choices was being made with it applied):

--- a/src/modules/module-switch-on-port-available.c
+++ b/src/modules/module-switch-on-port-available.c
@@ -256,7 +256,7 @@
                  p = i;
      if (!p)
          return NULL;
-    if (p->available != PA_AVAILABLE_NO)
+    if (p->available == PA_AVAILABLE_NO)
          return NULL;

      pa_assert_se(p = find_best_port(ports));


-- System Information:
Debian Release: 8.7
   APT prefers stable
   APT policy: (500, 'stable')
Architecture: amd64 (x86_64)
Foreign Architectures: i386