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bh=KEVzSR0/WjCxJZaMxPdW09tk7To83KQ0mBTy+N/F97s=; b=RMIk+BICDJ1nza/nR1dgcFTBUDDYekoElFE4wXJ996jjomAYcrz3bxwbYoPorWNlPBYKIR GVYR3/Tj5Mel3hLyDeVqAD0hRxK4e8Mx8CZCJiL7LperrBdvOgDFhvB30d/+2M0eckVQvg lC0veH5neEoaG5NY4vNuOaEVLP1UXXI= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-563-ICkpsGwgMG6zc1QnKm4T4g-1; Thu, 03 Dec 2020 10:15:44 -0500 X-MC-Unique: ICkpsGwgMG6zc1QnKm4T4g-1 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id BF73D9CC0E; Thu, 3 Dec 2020 15:15:42 +0000 (UTC) Received: from merkur.fritz.box (ovpn-114-175.ams2.redhat.com [10.36.114.175]) by smtp.corp.redhat.com (Postfix) with ESMTPS id F187718A2F; Thu, 3 Dec 2020 15:15:33 +0000 (UTC) Date: Thu, 3 Dec 2020 16:15:32 +0100 From: Kevin Wolf To: Paolo Bonzini Subject: Re: [PATCH 00/18] qapi/qom: QAPIfy object-add Message-ID: <20201203151532.GA5409@merkur.fritz.box> References: <3449b5d6-d094-84c8-a0ea-4cd25364db2d@redhat.com> <20201201220854.GC3836@habkost.net> <17afbbfe-209f-e4b2-e9e1-b50abe1fce3c@redhat.com> <20201202125124.GD3836@habkost.net> <69dff34f-d87b-3a8d-640f-35f6bf5db75c@redhat.com> <20201202135451.GE3836@habkost.net> <20201202151713.GE16765@merkur.fritz.box> <20201202160554.GG3836@habkost.net> <20201202173506.GH16765@merkur.fritz.box> <54637ad5-0662-24ea-d738-1d53e054a103@redhat.com> MIME-Version: 1.0 In-Reply-To: <54637ad5-0662-24ea-d738-1d53e054a103@redhat.com> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=kwolf@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=kwolf@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -35 X-Spam_score: -3.6 X-Spam_bar: --- X-Spam_report: (-3.6 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-1.495, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H3=0.001, RCVD_IN_MSPIKE_WL=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: lvivier@redhat.com, thuth@redhat.com, pkrempa@redhat.com, berrange@redhat.com, Eduardo Habkost , qemu-block@nongnu.org, libvir-list@redhat.com, armbru@redhat.com, jasowang@redhat.com, qemu-devel@nongnu.org, mreitz@redhat.com, kraxel@redhat.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Am 03.12.2020 um 12:11 hat Paolo Bonzini geschrieben: > On 02/12/20 18:35, Kevin Wolf wrote: > > > Could we have an intermediate state that doesn't require any > > > duplication and thus have no separate code paths that could > > > diverge? > > > > The one requirement we have for an intermediate state is that it > > supports both interfaces: The well-know create/set properties/realize > > dance, and a new DeviceClass method, say .create(), that takes the > > configuration in parameters instead of relying on previously set > > properties. > > > > I assumed two separate implementations of transferring the configuration > > into the internal state. On second thought, this assumption is maybe > > wrong. > > > > You can implement the new method as wrapper around the old way: It could > > just set all the properties and call realize. Of course, you don't win > > much in terms of improving the class implementation this way, but just > > support the new interface, but I guess it can be a reasonable > > intermediate step to resolve complicated dependencies etc. > > I sketched something at https://wiki.qemu.org/Features/QOM-QAPI_integration. > > The main difference with what we discussed so far is that it doesn't subsume > the complete/realize step, only the setting of properties. The idea is that > user_creatable_add_type does the following: > > - calls an oc->configure method on every superclass of the object > > - takes what's left of the input visitor and uses it to set properties > > - then calls ucc->complete > > So in the end the only new step is the first. If the first two steps are > bundled in a new function object_configure, they can be reused for devices, > machines and accelerators. > > The QAPI code generator can also easily wrap them into a C API for QOM > object creation. > > I glossed completely over the generation of properties within the QAPI code > generator. Making properties read-only (or, in the field-properties world, > having a default allow_set of "return false") is already a nice improvement > over I don't think this is an intermediate state like Eduardo wants to have. Creating the object, then setting properties, then realize [1] will fail after your change. But keeping it working was the whole point of the exercise. I'm also not really sure why you go from RngEgdOptions to QObject to a visitor, only to reconstruct RngEgdOptions at the end. I think the class implementations should have a normal C interface without visitors and we should be able to just pass the existing RngEgdOptions object (or the individual values for its fields for 'boxed': false). Kevin [1] Or complete for ucc, but the number of these is small enough that we don't really need any intermediate state, except maybe as a proof of concept for the later qdev conversion.