From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-3.5 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 28720C2D0A3 for ; Fri, 6 Nov 2020 15:52:06 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 4EC6922202 for ; Fri, 6 Nov 2020 15:52:05 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="AL1f08Oh" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 4EC6922202 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:45454 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1kb420-0003TH-99 for qemu-devel@archiver.kernel.org; Fri, 06 Nov 2020 10:52:04 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:43510) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1kb40T-0002xl-2M for qemu-devel@nongnu.org; Fri, 06 Nov 2020 10:50:29 -0500 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:38694) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.90_1) (envelope-from ) id 1kb40P-0000pS-JR for qemu-devel@nongnu.org; Fri, 06 Nov 2020 10:50:28 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1604677822; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=6ynUT4DFAzfwmjNY/qR5iqzqQv+jO2eldMg39BRjYuM=; b=AL1f08OhMw2iUjCgAk0VG2zb7FLIqkRKTWXsL4WIWiApFl+uyxLm9aLi/zVSxsH2FD1jZW v1F3TC+shbEbSQ3phkuizHnXQx6bs2gfHFK2KAjKB9Lsct0xUBAf7bfpOa0d2MZF19XzQj ZmrdMKkbg/xQhCFK8f+kToEslesWEbg= 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-259-DrXVrfOyMtOjSG8hw6JEwA-1; Fri, 06 Nov 2020 10:50:20 -0500 X-MC-Unique: DrXVrfOyMtOjSG8hw6JEwA-1 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 823761891E83; Fri, 6 Nov 2020 15:50:19 +0000 (UTC) Received: from localhost (ovpn-114-68.rdu2.redhat.com [10.10.114.68]) by smtp.corp.redhat.com (Postfix) with ESMTP id 504535D9CA; Fri, 6 Nov 2020 15:50:14 +0000 (UTC) Date: Fri, 6 Nov 2020 10:50:13 -0500 From: Eduardo Habkost To: Kevin Wolf Subject: Re: [PATCH v2 00/44] Make qdev static property API usable by any QOM type Message-ID: <20201106155013.GX5733@habkost.net> References: <20201104160021.2342108-1-ehabkost@redhat.com> <20201106094511.GA23864@merkur.fritz.box> MIME-Version: 1.0 In-Reply-To: <20201106094511.GA23864@merkur.fritz.box> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=ehabkost@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Received-SPF: pass client-ip=216.205.24.124; envelope-from=ehabkost@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/11/06 07:11:31 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 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_NONE=-0.0001, RCVD_IN_MSPIKE_H4=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: "Daniel P. Berrange" , Philippe =?utf-8?Q?Mathieu-Daud=C3=A9?= , qemu-devel@nongnu.org, Markus Armbruster , Paolo Bonzini , Igor Mammedov , =?utf-8?Q?Marc-Andr=C3=A9?= Lureau , John Snow , Stefan Berger Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Fri, Nov 06, 2020 at 10:45:11AM +0100, Kevin Wolf wrote: > Am 04.11.2020 um 16:59 hat Eduardo Habkost geschrieben: > > This series refactor the qdev property code so the static > > property system can be used by any QOM type. As an example, at > > the end of the series some properties in TYPE_MACHINE are > > converted to static properties to demonstrate the new API. > > > > Changes v1 -> v2 > > ---------------- > > > > * Rename functions and source files to call the new feature > > "field property" instead of "static property" > > > > * Change the API signature from an array-based interface similar > > to device_class_set_props() to a object_property_add()-like > > interface. > > > > This means instead of doing this: > > > > object_class_property_add_static_props(oc, my_array_of_props); > > > > properties are registered like this: > > > > object_class_property_add_field(oc, "property-name" > > PROP_XXX(MyState, my_field), > > prop_allow_set_always); > > > > where PROP_XXX is a PROP_* macro like PROP_STRING, PROP_BOOL, > > etc. > > In comparison, I really like the resulting code from the array based > interface in v1 better. > > I think it's mostly for two reasons: First, the array is much more > compact and easier to read. And maybe even more importantly, you know > it's static data and only static data. The function based interface can > be mixed with other code or the parameter list can contain calls to > other functions with side effects, so there are a lot more opportunities > for surprises. This is a really good point, and I strongly agree with it. Letting code do funny tricks at runtime is one of the reasons QOM properties became hard to introspect. > > What I didn't like about the v1 interface is that there is still a > separate object_class_property_set_description() for each property, but > I think that could have been fixed by moving the description to the > definitions in the array, too. This would be very easy to implement. > > On Fri, Oct 30, 2020 at 06:10:34PM +0100, Paolo Bonzini wrote: > > On 29/10/20 23:02, Eduardo Habkost wrote: > > > +static Property machine_props[] = { > > > + DEFINE_PROP_STRING("kernel", MachineState, kernel_filename), > > > + DEFINE_PROP_STRING("initrd", MachineState, initrd_filename), > > > + DEFINE_PROP_STRING("append", MachineState, kernel_cmdline), > > > + DEFINE_PROP_STRING("dtb", MachineState, dtb), > > > + DEFINE_PROP_STRING("dumpdtb", MachineState, dumpdtb), > > > + DEFINE_PROP_STRING("dt-compatible", MachineState, dt_compatible), > > > + DEFINE_PROP_STRING("firmware", MachineState, firmware), > > > + DEFINE_PROP_STRING("memory-backend", MachineState, ram_memdev_id), > > > + DEFINE_PROP_END_OF_LIST(), > > > +}; > > > + > > > > While I think generalizing the _code_ for static properties is obviously > > a good idea, I am not sure about generalizing the interface for adding them. > > > > The reason is that we already have a place for adding properties in > > class_init, and having a second makes things "less local", so to speak. > > As long as you have the function call to apply the properites array in > .class_init, it should be obvious enough what you're doing. > > Of course, I think we should refrain from mixing both styles in a single > object, but generally speaking the array feels so much better that I > don't think we should reject it just because QOM only had a different > interface so far (and the property array is preexisting in qdev, too, so > we already have differences between objects - in fact, the majority of > objects is probably qdev today). This is also a strong argument. The QEMU code base has ~500 matches for "object*_property_add*" calls, and ~2100 for "DEFINE_PROP*". Converting qdev arrays to object_class_property_add_*() calls would be a huge effort with no gains. The end result would be two different APIs for registering class field properties coexisting for a long time, and people still confused on what's the preferred API. -- Eduardo