Multi seat with nested servers?

Pekka Paalanen ppaalanen at
Fri Dec 9 08:40:57 UTC 2022

On Thu, 08 Dec 2022 11:47:45 -0500
Phillip Susi <phill at> wrote:

> Only one Wayland server can control a given GPU, but if you have two
> monitors on one GPU, isn't it possible to run a root server that
> displays two nested servers each on their own monitor to get a multi
> seat setup?


> Has anyone done this?  What would a good server be to use for the root?

I don't know.

There are two different approaches:
- nested compositor presents to the root compositor which presents to KMS
- nested compositor uses KMS leasing offered by the root compositor,
  and presents to KMS directly

In the leasing case, the root compositor may not need to be even a
Wayland server nor a compositor. It could be a system daemon like
seatd or logind, if they offered the API for it.

> Could you have the nested servers directly bind to their keyboard/mouse
> or would the root server also have to multiplex those out to the nested
> servers?

In the root compositor case, the root server would indeed need to proxy
the input as well. That would maintain security.

OTOH, in the leasing case, if the lease daemon is also leasing out
input devices (like seatd and logind already do today), input would not
need to be proxied.

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