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Re: [PATCH 1/9] qapi: New special feature flag "unstable"
From: |
Dr. David Alan Gilbert |
Subject: |
Re: [PATCH 1/9] qapi: New special feature flag "unstable" |
Date: |
Tue, 26 Oct 2021 10:22:15 +0100 |
User-agent: |
Mutt/2.0.7 (2021-05-04) |
* Kevin Wolf (kwolf@redhat.com) wrote:
> Am 25.10.2021 um 07:25 hat Markus Armbruster geschrieben:
> > By convention, names starting with "x-" are experimental. The parts
> > of external interfaces so named may be withdrawn or changed
> > incompatibly in future releases.
> >
> > Drawback: promoting something from experimental to stable involves a
> > name change. Client code needs to be updated.
> >
> > Moreover, the convention is not universally observed:
> >
> > * QOM type "input-barrier" has properties "x-origin", "y-origin".
> > Looks accidental, but it's ABI since 4.2.
> >
> > * QOM types "memory-backend-file", "memory-backend-memfd",
> > "memory-backend-ram", and "memory-backend-epc" have a property
> > "x-use-canonical-path-for-ramblock-id" that is documented to be
> > stable despite its name.
> >
> > We could document these exceptions, but documentation helps only
> > humans. We want to recognize "unstable" in code, like "deprecated".
> >
> > Replace the convention by a new special feature flag "unstable". It
> > will be recognized by the QAPI generator, like the existing feature
> > flag "deprecated", and unlike regular feature flags.
> >
> > This commit updates documentation and prepares tests. The next commit
> > updates the QAPI schema. The remaining patches update the QAPI
> > generator and wire up -compat policy checking.
> >
> > Signed-off-by: Markus Armbruster <armbru@redhat.com>
>
> Obviously, replacing the old convention gets rid of the old drawbacks,
> but adds a new one: While using x- makes it very obvious for a human
> user that this is an unstable feature, a feature flag in the schema will
> almost certainly go unnoticed in manual use.
Agreed, I'd keep the x- as well.
Having said that, the x- represents a few different things (that we
don't currently distinguish):
- experimental
- for internal use
- for debugging/human use
Dave
> Kevin
>
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK
- [PATCH 1/9] qapi: New special feature flag "unstable", (continued)
- [PATCH 1/9] qapi: New special feature flag "unstable", Markus Armbruster, 2021/10/25
- Re: [PATCH 1/9] qapi: New special feature flag "unstable", John Snow, 2021/10/25
- Re: [PATCH 1/9] qapi: New special feature flag "unstable", Kevin Wolf, 2021/10/26
- Re: [PATCH 1/9] qapi: New special feature flag "unstable", Markus Armbruster, 2021/10/26
- Re: [PATCH 1/9] qapi: New special feature flag "unstable", Kevin Wolf, 2021/10/26
- Re: [PATCH 1/9] qapi: New special feature flag "unstable", Markus Armbruster, 2021/10/28
- Re: [PATCH 1/9] qapi: New special feature flag "unstable", Daniel P . Berrangé, 2021/10/26
- Re: [PATCH 1/9] qapi: New special feature flag "unstable", Markus Armbruster, 2021/10/26
- Re: [PATCH 1/9] qapi: New special feature flag "unstable", Daniel P . Berrangé, 2021/10/26
- Re: [PATCH 1/9] qapi: New special feature flag "unstable", Markus Armbruster, 2021/10/27
[PATCH 9/9] qapi: Extend -compat to set policy for unstable interfaces, Markus Armbruster, 2021/10/25