[PATCH BlueZ] audio/transport: Only store volume when also emitting DBus prop change

[Marijn Suijten <marijn.suijten@somainline.org>]

By setting a2dp->volume early in set_volume() the resulting call to
media_transport_update_volume() when an AVRCP reply is received will
likely see the same volume received (unless the peer rounded it to
another value) and bail on equality, before emitting a DBus property
change.  This results in DBus clients not being made aware of the change
unless the peer is an audio source (that receives a notification about
changed volume, instead of a command to _set_ a new volume), where
set_volume() immediately raises the DBus signal.

This issue is observed when playing back audio to headphones through an
AbsoluteVolume-enabled audio server like PulseAudio, which does not
receive the "Volume" change (while the peer does change volume) when
setting this property externally using ie. dbus-send.
---
 profiles/audio/transport.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/profiles/audio/transport.c b/profiles/audio/transport.c
index 8248014ae..d158fc97a 100644
--- a/profiles/audio/transport.c
+++ b/profiles/audio/transport.c
@@ -659,14 +659,14 @@ static void set_volume(const GDBusPropertyTable *property,
 	if (a2dp->volume == volume)
 		return;
 
-	a2dp->volume = volume;
-
 	notify = transport->source_watch ? true : false;
-	if (notify)
+	if (notify) {
+		a2dp->volume = volume;
 		g_dbus_emit_property_changed(btd_get_dbus_connection(),
 						transport->path,
 						MEDIA_TRANSPORT_INTERFACE,
 						"Volume");
+	}
 
 	avrcp_set_volume(transport->device, volume, notify);
 	return;
-- 
2.32.0