FIXUP: "delay absolute volume setup": unconditionally set for source

See code comments why

src/modules/bluetooth/bluez5-util.c

@@ -741,12 +741,15 @@ static void bluez5_transport_request_volume(pa_bluetooth_transport *t) {
     send_and_add_to_pending(t->device->discovery, m, request_volume_reply, t);
 }
 
-void pa_bluetooth_transport_setup_a2dp_absolute_volume(pa_bluetooth_transport *t) {
+void pa_bluetooth_transport_load_a2dp_sink_volume(pa_bluetooth_transport *t) {
     pa_assert(t);
 
-    if (t->profile == PA_BLUETOOTH_PROFILE_A2DP_SINK || t->profile == PA_BLUETOOTH_PROFILE_A2DP_SOURCE)
+    if (t->profile == PA_BLUETOOTH_PROFILE_A2DP_SINK)
         /* A2DP Absolute Volume control (AVRCP 1.4) is optional */
         bluez5_transport_request_volume(t);
+    else
+        pa_assert_not_reached();
+
 }
 
 bool pa_bluetooth_device_any_transport_connected(const pa_bluetooth_device *d) {

src/modules/bluetooth/bluez5-util.h

@@ -196,7 +196,7 @@ void pa_bluetooth_transport_set_state(pa_bluetooth_transport *t, pa_bluetooth_tr
 void pa_bluetooth_transport_put(pa_bluetooth_transport *t);
 void pa_bluetooth_transport_unlink(pa_bluetooth_transport *t);
 void pa_bluetooth_transport_free(pa_bluetooth_transport *t);
-void pa_bluetooth_transport_setup_a2dp_absolute_volume(pa_bluetooth_transport *t);
+void pa_bluetooth_transport_load_a2dp_sink_volume(pa_bluetooth_transport *t);
 
 bool pa_bluetooth_device_any_transport_connected(const pa_bluetooth_device *d);
 bool pa_bluetooth_device_switch_codec(pa_bluetooth_device *device, pa_bluetooth_profile_t profile, pa_hashmap *capabilities_hashmap, const pa_a2dp_codec *a2dp_codec, void (*codec_switch_cb)(bool, pa_bluetooth_profile_t profile, void *), void *userdata);

src/modules/bluetooth/module-bluez5-device.c

@@ -1085,6 +1085,18 @@ static int add_source(struct userdata *u) {
         || u->profile == PA_BLUETOOTH_PROFILE_HFP_HF) {
         pa_source_set_set_volume_callback(u->source, source_set_volume_cb);
         u->source->n_volume_steps = 16;
+    } else if (u->profile == PA_BLUETOOTH_PROFILE_A2DP_SOURCE) {
+        pa_assert(u->transport->profile == PA_BLUETOOTH_PROFILE_A2DP_SOURCE);
+
+        /* Absolute Volume is optional but BlueZ unconditionally reports
+         * feature category 2, meaning supporting it is mandatory.
+         * PulseAudio can and should perform the attenuation anyway in,
+         * the source role as it is the audio rendering device.
+         */
+        // TODO: Send initial (restored) volume to the device, letting it know we are performing attenuation.
+        pa_source_set_set_volume_callback(u->source, source_set_volume_cb);
+        pa_source_set_set_mute_callback(u->source, source_set_mute_cb);
+        u->source->n_volume_steps = A2DP_MAX_GAIN + 1;
     }
     return 0;
 }
@@ -1423,8 +1435,6 @@ static int init_profile(struct userdata *u) {
                 PA_SINK_IS_LINKED(u->sink->state),
                 u->sink->monitor_source ? PA_SOURCE_IS_LINKED(u->sink->monitor_source->state) : -1);
 
-    // pa_bluetooth_transport_setup_a2dp_absolute_volume(u->transport);
-
     return r;
 }
 
@@ -1759,6 +1769,22 @@ static int start_thread(struct userdata *u) {
         if (u->a2dp_codec)
             pa_proplist_sets(u->card->proplist, PA_PROP_BLUETOOTH_CODEC, u->a2dp_codec->name);
 
+    /* Now that everything is set up we are ready to check for the Volume property.
+     * Sometimes its initial "change" notification arrives too early when the sink
+     * is not available or still in UNLINKED state; check it again here to know if
+     * our sink peer supports Absolute Volume; in that case we should not perform
+     * any attenuation but delegate all set_volume calls to the peer through this
+     * Volume property.
+     *
+     * Note that this works the other way around if the peer is in source profile:
+     * we are rendering audio and hence responsible for applying attenuation. The
+     * set_volume callback is always registered, and Volume is always passed to
+     * BlueZ unconditionally. BlueZ only sends a notification to the peer if it
+     * registered a notification request for absolute volume previously.
+     */
+    if (u->transport && u->sink)
+        pa_bluetooth_transport_load_a2dp_sink_volume(u->transport);
+
     return 0;
 }
 
@@ -2112,9 +2138,6 @@ static int set_profile_cb(pa_card *c, pa_card_profile *new_profile) {
         if (start_thread(u) < 0)
             goto off;
 
-    if (u->transport)
-        pa_bluetooth_transport_setup_a2dp_absolute_volume(u->transport);
-
     return 0;
 
 off:
@@ -2403,29 +2426,6 @@ static pa_hook_result_t transport_sink_volume_changed_cb(pa_bluetooth_discovery
     return PA_HOOK_OK;
 }
 
-static void source_set_a2dp_remote_controlled(pa_source *s) {
-    struct userdata *u;
-
-    pa_assert(s);
-
-    if (s->set_volume == source_set_volume_cb)
-        return;
-
-    pa_assert(s->core);
-
-    u = s->userdata;
-    pa_assert(u);
-    pa_assert(u->source == s);
-    pa_assert(u->transport);
-    pa_assert(u->transport->profile == PA_BLUETOOTH_PROFILE_A2DP_SOURCE);
-
-    pa_log_debug("%s: Enabling volume notifications for A2DP peer", s->name);
-
-    pa_source_set_set_volume_callback(s, source_set_volume_cb);
-    pa_source_set_set_mute_callback(s, source_set_mute_cb);
-    s->n_volume_steps = A2DP_MAX_GAIN + 1;
-}
-
 static pa_hook_result_t transport_source_volume_changed_cb(pa_bluetooth_discovery *y, pa_bluetooth_transport *t, struct userdata *u) {
     pa_volume_t volume;
     pa_cvolume v;
@@ -2446,8 +2446,6 @@ static pa_hook_result_t transport_source_volume_changed_cb(pa_bluetooth_discover
             return PA_HOOK_OK;
         }
 
-        source_set_a2dp_remote_controlled(u->source);
-
         // TODO: Apply to HSP too
         if (volume <= A2DP_MUTE_VOLUME) {
             pa_source_mute_changed(u->source, true);
@@ -2497,9 +2495,6 @@ static void switch_codec_cb_handler(bool success, pa_bluetooth_profile_t profile
     pa_log_info("Codec successfully switched to %s with profile: %s",
             u->a2dp_codec->name, pa_bluetooth_profile_to_string(u->profile));
 
-    if (u->transport)
-        pa_bluetooth_transport_setup_a2dp_absolute_volume(u->transport);
-
     return;
 
 off:
@@ -2806,9 +2801,6 @@ int pa__init(pa_module* m) {
                 PA_SINK_IS_LINKED(u->sink->state),
                 u->sink->monitor_source ? PA_SOURCE_IS_LINKED(u->sink->monitor_source->state) : -1);
 
-    if (u->transport)
-        pa_bluetooth_transport_setup_a2dp_absolute_volume(u->transport);
-
     message_handler_path = make_message_handler_path(u->card->name);
     pa_message_handler_register(m->core, message_handler_path, "Bluez5 device message handler",
             bluez5_device_message_handler, (void *) u);