[systemd-devel] logind: multiseat without framebuffer graphic cards

[Lennart Poettering]

On Thu, 22.11.12 23:04, Oleg Samarin (osamarin68 at gmail.com) wrote:

> В Ср., 21/11/2012 в 20:23 +0100, Lennart Poettering пишет:
> 
> > I think there are other ways thinkable, where we don't have to add
> > explicit nvidia-compatibility switches. For example, instead of
> > explicitly watching for fb devices to show up before we consider a seat
> > to be around, we could instead look for devices that are tagged with a
> > special tag ("tag" as in udev's TAG= construct) -- we'd then tag all fb
> > devices out-of-the-box this way, and people who want to use the nvidia
> > binary driver can attach that tag to some kernel device the nvidia
> > driver exposes, but I wouldn't have to care about that, and systemd
> > upstream wouldn't need to know what people do locally. And maybe you
> > could even convince Nvidia to ship the udev rule that attaches this tag
> > in their drivers. By doing things this way we'd not introduce the race
> > that your patch would introduce, but we'd not hardcode anything directly
> > to fb devices.
> > 
> > Note that in systemd we generally try to fix this things properly, and
> > not work-around things. Now, your global swicth didn't appear as a
> > "proper fix" to me, due to the race issues. But the solution with a udev
> > tag otoh sounds like a worthwile fix that makes logind cleaner -- and
> > which as a side-effect allows you to integrate things with your nvidia
> > driver.
> > 
> > Does that make some sense?
> 
> OK. So we need two changes:
> 
> (1). Introduce a new udev tag that means "master device" for the seat.
> Support it with logind.c. Add an udev rule that sets this tag for all
> framebuffer device

Yes, and please name this tag "seat-master".

> (2). multi-seat-x should not trigger an error if there is no framebufer
> device exist on the seat. It is a temporary stuff until X can get device
> from -seat, so it may look for a specially named config file or just
> start X without any addition parameters (or with -sharevts only)

I'd much prefer if this was done in X instead. i.e. via matching the
-seat parameter when parsing configuration files.

i.e. xorg.conf currently already knows:

        MatchProduct
        MatchDevicePath
        MatchTag
        MatchDriver

Maybe introducing a MatchSeat construct in this style would be the best solution?

Lennart

-- 
Lennart Poettering - Red Hat, Inc.