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. 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. Cheers, Mikel
