[Spice-devel] [PATCH v4 0/2] protocol: add gl scanout support

[Gerd Hoffmann]

  Hi,

> Then we realize in order to achieve X or Y, we need to do things
> slightly differently. What is our escape plan there? Do we have an easy
> way out without breaking older clients?

It's all guarded by the capability.  So, yes, there is a sane backup
plan.

If we figure later we screwed up things so badly that we have to redo
things we can use that to migrate to a better protocol extension, using
a different capability.  We can choose whenever we want spice-server
support both old and new extension in parallel (for smooth migration) or
not (if that happens to not be possible for whatever reason).  Heck, we
can even discontinue support by having spice-server not advertising the
capability any more.

So, the only issue is that this will linger in spice-protocol forever,
even if we stop using it in server and client at some point in the
future.  I don't think this is a big problem.

cheers,
  Gerd