On Tue, 2012-12-04 at 08:18 +0100, Mikel Astiz wrote: > Hi Tanu, > > On Tue, Dec 4, 2012 at 1:43 AM, Tanu Kaskinen <tanuk at iki.fi> wrote: > > On Mon, 2012-12-03 at 10:57 +0100, Mikel Astiz wrote: > >> On Sun, Dec 2, 2012 at 4:05 AM, Tanu Kaskinen <tanuk at iki.fi> wrote: > >> > On Thu, 2012-11-29 at 14:33 +0100, Mikel Astiz wrote: > >> >> On Thu, Nov 29, 2012 at 4:55 AM, Tanu Kaskinen <tanuk at iki.fi> wrote: > >> >> > so that INIT->IDLE transitions will work too, if we decide some day that > >> >> > it's not a good idea to start the devices suspended. (I think it makes > >> >> > sense to start them suspended, but relying on module-suspend-on-idle for > >> >> > unsuspending is not good.) > >> >> > >> >> INIT->IDLE should already be working, since in this case the transport > >> >> is acquired before the thread is started. I just sent two patches > >> >> that would do this for headsets, since Arun was > >> >> also concerned about relying on the presence of > >> >> module-suspend-on-idle. > >> > > >> > Would the acquire in setup_transport() be necessary at all if the > >> > transport would be acquired in the PA_SINK_MESSAGE_SET_STATE handler > >> > also for the INIT->IDLE transition? > >> > >> I believe that the acquire would always be necessary in > >> setup_transport(), since this is the only way to find out which the > >> initial state of the sink/sources should be. > > > > The initial state should always be IDLE for headsets, so in that case > > there's nothing to decide, right? (Until the suspend-on-idle interaction > > gets sorted out, that is.) For a2dp_source/hfgw, couldn't you figure out > > the initial sink/source state from the bluetooth stream state instead of > > checking whether the transport has been acquired? If the stream is not > > playing, start suspended. > > The issue is indeed about a2dp_source/hfgw. > > The problem with checking the state before you acquire is that it's > racy: by the time you reach MESSAGE_SET_STATE (or even worse, the > BlueZ daemon) the state might have already changed. So the only real > way to confirm that the audio is streaming by acquiring. I see. > This is not a strong argument for BlueZ 4.x since the D-Bus API does > not support such atomic test&set acquisitions (optional acquire). > That's why we have a FIXME in bt_transport_acquire(), where a similar > behavior is simulated but is still racy. However, this has already > been fixed for BlueZ 5 so I would suggest we continue with this > approach, so we don't have to move more code around in the near > future. Yes, I agree. -- Tanu
