[systemd-devel] Preventing automatic seat assignments

[David Herrmann]

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
David