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[82.30.61.225]) by smtp.gmail.com with ESMTPSA id v191sm23799wme.36.2021.10.26.02.22.17 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 26 Oct 2021 02:22:18 -0700 (PDT) Date: Tue, 26 Oct 2021 10:22:15 +0100 From: "Dr. David Alan Gilbert" To: Kevin Wolf Subject: Re: [PATCH 1/9] qapi: New special feature flag "unstable" Message-ID: References: <20211025052532.3859634-1-armbru@redhat.com> <20211025052532.3859634-2-armbru@redhat.com> MIME-Version: 1.0 In-Reply-To: User-Agent: Mutt/2.0.7 (2021-05-04) Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=dgilbert@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Received-SPF: pass client-ip=216.205.24.124; envelope-from=dgilbert@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -27 X-Spam_score: -2.8 X-Spam_bar: -- X-Spam_report: (-2.8 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H2=-0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: pkrempa@redhat.com, berrange@redhat.com, ehabkost@redhat.com, qemu-block@nongnu.org, quintela@redhat.com, qemu-devel@nongnu.org, eblake@redhat.com, mdroth@linux.vnet.ibm.com, Markus Armbruster , libvir-list@redhat.com, pbonzini@redhat.com, marcandre.lureau@redhat.com, jsnow@redhat.com, libguestfs@redhat.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" * 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 of external interfaces so named may be withdrawn or changed 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 > > 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