Multi seat with nested servers?

Phillip Susi phill at
Fri Dec 9 15:09:02 UTC 2022

Pekka Paalanen <ppaalanen at> writes:

> 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.

How does this leasing work?  Does it lease the entire GPU or can it
lease only one display?  I would imagine it would be the entire GPU, in
which case you couldn't lease it to both servers.

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

Why do you say that?

> 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.

What is this leasing you speak of?  AFAIUI, logind just maintains a
database of what input devices belong to what seats so that the display
server can query it and find out which devices it should open.

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