[pulseaudio-discuss] [PATCH v1 0/3] bluetooth: Headset port availability

[Tanu Kaskinen]

On Tue, 2013-02-05 at 08:44 +0100, David Henningsson wrote:
> On 02/04/2013 05:06 PM, Tanu Kaskinen wrote:
> > If the phone uses PulseAudio path configuration files for the ALSA
> > configuration, the Bluetooth port could be flagged with a property. If
> > the phone uses UCM, I think the UCM configuration should provide the
> > information, and the port flagged accordingly. If an ALSA port is
> > flagged that way, I guess alsa-card should not create a routing endpoint
> > in that case. The endpoint would be created by module-bluetooth-device.
> 
> Routing endpoints aside, if it is a technical impossibility / major 
> inconvenience to have a single port for a single physical entity, one 
> could have a port property "master-port" which would link the ports 
> together.

I don't think the Bluetooth module would implement ports for HSP in this
case, so there would be no master port to link to.

> But how is exclusivity handled here? I mean, how would you encode the 
> fact that A2DP should not be used at the same time as HSP, if they don't 
> belong to the same card?

The headset endpoint could keep the HSP sink and source suspended while
the Bluetooth card has an A2DP profile active. If there are no Bluetooth
cards, maybe the ALSA card should keep the HSP sink and source suspended
until a Bluetooth card appears and takes control. When the Bluetooth
card has the HSP profile active, there's no problem with concurrent HSP
and A2DP use: in that case there are no A2DP sinks or sources at all.

> I mean, one of the basic properties of two different cards is that they 
> are independent of each other, if this is not the case, should we 
> consider merging the bluetooth and ALSA cards instead? (That is just 
> brainstorming, not an actual proposal)

I don't think merging the cards is necessary, nor desirable. The ALSA
card can have also other functions than being a gateway to the Bluetooth
adapter, and those functions should be available regardless of whether
there are any Bluetooth devices connected or not. The HSP port can't be
separated from the ALSA card either, because those other functions may
be mutually exclusive with the HSP port, so the ALSA card must know when
the HSP port is being used.

-- 
Tanu