[systemd-devel] Preventing automatic seat assignments

Tanu Kaskinen tanu.kaskinen at linux.intel.com
Wed Aug 27 01:47:31 PDT 2014

On Tue, 2014-08-26 at 14:00 +0200, Lennart Poettering wrote:
> On Tue, 26.08.14 12:17, Tanu Kaskinen (tanu.kaskinen at linux.intel.com) wrote:
> > Hi,
> > 
> > If I want to designate some sound card to be shared between seats,
> > then I suppose that sound card shouldn't be assigned to any seats.
> > However, currently /usr/lib/udev/rules.d/71-seat.rules
> > unconditionally tags all sound cards with the "seat" tag. How should
> > this be solved?
> What's the rationale here actually? PA doesn't really support "sharing"
> sound cards between multiple seats.
> I mean, If this is something generally useful we can see if we can
> support that in the default rules, but I am not seeing it?

The use case is a car audio system. There are multiple seats, and each
seat can have dedicated audio hardware (e.g. headphones), but there's
also the speaker system that is shared by all seats.

It's true that PA needs modifications too to support this. We haven't
yet decided how to implement this, but probably we will run PA in system
mode for the shared devices only, and user instances for the per-seat
hardware. The user instances will use the tunnel module to connect to
the hardware that is managed by the system instance.


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