From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Sender: List-Post: List-Help: List-Unsubscribe: List-Subscribe: Received: from lists.oasis-open.org (oasis-open.org [10.110.1.242]) by lists.oasis-open.org (Postfix) with ESMTP id 42D269862AF for ; Mon, 21 Mar 2022 16:36:31 +0000 (UTC) From: Cornelia Huck In-Reply-To: <15118124.lv8FRMpzUk@silver> References: <4735344.EBYxvr1mta@silver> <11686863.Z9n2BMzBuM@silver> <20220318170625.0d2be174.pasic@linux.ibm.com> <15118124.lv8FRMpzUk@silver> Date: Mon, 21 Mar 2022 17:36:26 +0100 Message-ID: <87pmmfqn3p.fsf@redhat.com> MIME-Version: 1.0 Subject: Re: [virtio-comment] Re: [PATCH v3 4/4] Add CCW configuration field "indirect_num" Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable To: Christian Schoenebeck , Halil Pasic Cc: virtio-comment@lists.oasis-open.org, Stefan Hajnoczi , Greg Kurz , Dominique Martinet List-ID: On Sat, Mar 19 2022, Christian Schoenebeck wrote: > On Freitag, 18. M=C3=A4rz 2022 17:06:25 CET Halil Pasic wrote: >> I agree that the "including" is important, but I'm not sure about the >> "its contents are undefined". I don't really understand why should we us= e >> a plural here. What speaks against specifying that in SHOULD be stored >> as 0 by the device, and MUST be ignored by the driver? > > Both solutions would be viable. Personally I would just use something lik= e=20 > "Should be zero" if there is a value in recommending that, but I don't se= e a=20 > value in recommending to set something to zero and at the same time requi= ring=20 > to not access it in the first place. > >> Currently we say that \field{max_indirect_num} exists like a be32 field >> even if VIRTIO_RING_F_INDIRECT_SIZE is not negotiated. Which kind of >> implies that at least type invariants should hold. Of course, there is >> none here (i.e. every bits value is also a be32 value), but for somethin= g >> like an enum interesting corner cases can pop up. > > I can't follow you on that one. What has that do with enums in this case? > > Anyway, I won't persist on my suggestion to use the (IMO more compact for= m)=20 > "undefined". If you guys prefer the more specific solution "SHOULD be 0 a= nd=20 > MUST not be accessed" then I will go that way. I'm not sure what mandating 0 and non-access would buy us here... the driver can of course read the field (e.g. when copying the structure wholesale); it just can't make use of the contents when it did not negotiate the feature (but why would it do so in that case anyway?) Also, I think junk remains junk, whether it is a be32 field or interpreted as an enum. It is simply not valid, even if it might by accident end up to be a defined enum value. So I think "undefined" should be fine. This publicly archived list offers a means to provide input to the=0D OASIS Virtual I/O Device (VIRTIO) TC.=0D =0D In order to verify user consent to the Feedback License terms and=0D to minimize spam in the list archive, subscription is required=0D before posting.=0D =0D Subscribe: virtio-comment-subscribe@lists.oasis-open.org=0D Unsubscribe: virtio-comment-unsubscribe@lists.oasis-open.org=0D List help: virtio-comment-help@lists.oasis-open.org=0D List archive: https://lists.oasis-open.org/archives/virtio-comment/=0D Feedback License: https://www.oasis-open.org/who/ipr/feedback_license.pdf= =0D List Guidelines: https://www.oasis-open.org/policies-guidelines/mailing-lis= ts=0D Committee: https://www.oasis-open.org/committees/virtio/=0D Join OASIS: https://www.oasis-open.org/join/