Re: [patch] spec: Update alsa namespace to include virtual device

Hi Lennart,

quoted

At some point in the future we gonna integrate Bluetooth much deeper
into HAL as currently done. Right now we only see the kernel side of
Bluetooth represented in HAL. This needs some restructure to make it
work smoothly and needs some extra time, but we are getting there.

If the bt devices are exported in sysfs in the kernel already it is no
longer hal that synthesizes them. Which makes these things much
cleaner I would say.

Synthesizing virtual devices at the HAL level doesn't look like such a
good idea to me, smells kludgy. But doing this on a lower level might
make sense.

the physical link (the piconet connection) is exported via the kernel
and visible via sysfs. If you run RFCOMM (serial port), BNEP (network)
or HIDP (input) over it then it links it together. If the protocol runs
in userspace like A2DP for stereo headsets then the kernel knows nothing
about it and can't link it together. This also means that HAL can't do
anything about it since it lacks these information.

In the overall end there should be no difference in a physical sound
card or a virtual one that use Bluetooth (or Wireless USB or whatever).
The only big difference is actually that these are connected or
disconnected. It is more than hotplug since we can virtually plugin
these devices by connecting to them. And so on. Not really trivial to
solve. My current goal is the less userspace application need to know
the better.

quoted

quoted

OTOH i must say that this would make it very easy for me to add bt
support to PA, so I am not inherently opposed. However, I don't really
think going through ALSA for bt audio makes too much sense for PA. It
is probably better to integrate bt and PA directly, without having
this unnecessary abstraction in between.

I am currently working on the GStreamer sink. If you provide an exported
plugin API for PulseAudio, you can have that easily. Otherwise it might
not happen.

A stable plugin API is not going to happen anytime soon, sorry. Also,
it is not really practical to develop plugins out-of-tree. I
acknowledge the demand for it, but the plugin API is just too quickly
moving.

Hmm, I'd love to add proper BT support to PA myself, but unfortunately
I lack the hardware for it. It would be much easier to keep it up to
date for me then.

We are in a chicken-egg situation here. To write a plugin you need to
use our SBC encoder and our IPC. Both of them are internal only.

Regards

Marcel


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