[systemd-devel] Preventing automatic seat assignments

[Tanu Kaskinen]

On Wed, 2014-09-10 at 12:44 +0200, David Herrmann wrote:
> Hi
> 
> On Tue, Sep 9, 2014 at 10:49 AM, Tanu Kaskinen
> <tanu.kaskinen at linux.intel.com> wrote:
> > On Wed, 2014-08-27 at 11:47 +0300, Tanu Kaskinen wrote:
> >> 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.
> >
> > Ping?
> 
> Sorry, a lot of people are on vacation..
> 
> I think the right solution for this is to support "TAGS-=seat" in
> udev. That is, the automatic seat-assignment will still be applied,
> but you can revert it in your own udev rules. By dropping the "seat"
> tag, logind will not treat it as 'seated' device.

Thanks for the reply. The way you put it sounds like udev doesn't
currently support "TAGS-=seat". Is that correct? If so, maybe I'll look
into making a patch at some point, but no promises.

-- 
Tanu