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 Received: from ws5-mx01.kavi.com (ws5-mx01.kavi.com [34.193.7.191]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 71C45C54E49 for ; Mon, 26 Feb 2024 12:36:53 +0000 (UTC) Received: from lists.oasis-open.org (oasis.ws5.connectedcommunity.org [10.110.1.242]) by ws5-mx01.kavi.com (Postfix) with ESMTP id C51F378142 for ; Mon, 26 Feb 2024 12:36:52 +0000 (UTC) Received: from lists.oasis-open.org (oasis-open.org [10.110.1.242]) by lists.oasis-open.org (Postfix) with ESMTP id BCFB4986478 for ; Mon, 26 Feb 2024 12:36:52 +0000 (UTC) Received: from host09.ws5.connectedcommunity.org (host09.ws5.connectedcommunity.org [10.110.1.97]) by lists.oasis-open.org (Postfix) with QMQP id B1FE3986364; Mon, 26 Feb 2024 12:36:52 +0000 (UTC) Mailing-List: contact virtio-dev-help@lists.oasis-open.org; run by ezmlm List-ID: Sender: Precedence: bulk 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 A2B7398635B for ; Mon, 26 Feb 2024 12:36:49 +0000 (UTC) X-Virus-Scanned: amavisd-new at kavi.com X-MC-Unique: vpmPKEoUP32DJ8JW_UvdYQ-1 From: Cornelia Huck To: Marc Kleine-Budde , Matias Ezequiel Vara Larsen Cc: Mikhail Golubev-Ciuchea , virtio-comment@lists.oasis-open.org, virtio-dev@lists.oasis-open.org, linux-can@vger.kernel.org, Harald Mommer In-Reply-To: <20240221-juggling-uproar-9518b4901f41-mkl@pengutronix.de> Organization: "Red Hat GmbH, Sitz: Werner-von-Siemens-Ring 12, D-85630 Grasbrunn, Handelsregister: Amtsgericht =?utf-8?Q?M=C3=BCnchen=2C?= HRB 153243, =?utf-8?Q?Gesch=C3=A4ftsf=C3=BChrer=3A?= Ryan Barnhart, Charles Cachera, Michael O'Neill, Amy Ross" References: <20230609142243.199074-1-Mikhail.Golubev-Ciuchea@opensynergy.com> <20240221-acts-decade-76d3d69e8e4d-mkl@pengutronix.de> <20240221-juggling-uproar-9518b4901f41-mkl@pengutronix.de> User-Agent: Notmuch/0.37 (https://notmuchmail.org) Date: Mon, 26 Feb 2024 13:36:40 +0100 Message-ID: <877circsh3.fsf@redhat.com> MIME-Version: 1.0 Content-Type: text/plain X-Scanned-By: MIMEDefang 3.4.1 on 10.11.54.10 Subject: Re: [virtio-dev] Re: [virtio-comment] [RFC PATCH v3] virtio-can: Device specification. On Wed, Feb 21 2024, Marc Kleine-Budde wrote: > On 21.02.2024 14:16:54, Matias Ezequiel Vara Larsen wrote: >> On Wed, Feb 21, 2024 at 01:49:31PM +0100, Marc Kleine-Budde wrote: >> > On 21.02.2024 11:37:58, Matias Ezequiel Vara Larsen wrote: >> > > > > +The length of the \field{sdu} is determined by the \field{length}. >> > > > > + >> > > > > +The type of a CAN message identifier is determined by \field{flags}. The >> > > > > +3 most significant bits of \field{can_id} do not bear the information >> > > > > +about the type of the CAN message identifier and are 0. >> > > > > + >> > > > > +The device MUST reject any CAN frame type for which support has not been >> > > > > +negotiated with VIRTIO_CAN_RESULT_NOT_OK in \field{result} and MUST NOT >> > > > > +schedule the message for transmission. A CAN frame with an undefined bit >> > > > > +set in \field{flags} is treated like a CAN frame for which support has >> > > > > +not been negotiated. >> > > > > + >> > > > > +The device MUST reject any CAN frame for which \field{can_id} or >> > > > > +\field{sdu} length are out of range or the CAN controller is in an >> > > > > +invalid state with VIRTIO_CAN_RESULT_NOT_OK in \field{result} and MUST >> > > > > +NOT schedule the message for transmission. >> > > > > + >> > > I am not very familiar with CAN but how does the device figure out that >> > > the can_id is out of range? >> > >> > In classical CAN we have the standard CAN frames, which have an 11 bit >> > ID, and there are extended CAN frames, which have 29 bits ID. Extended >> > frames are signaled with VIRTIO_CAN_FLAGS_EXTENDED set. >> > >> > So if a standard frame uses more than 11 Bits of CAN-ID, it's considered >> > out of range. > > Another option would be an extended frame (VIRTIO_CAN_FLAGS_EXTENDED > set) and using more than 29 bits. > >> Thanks Marc for the explanation. Do you think that it would be >> worthwhile to add that to the spec at some point? > > Yes that makes sense as it clarifies what's meant by out of range for > CAN-IDs, for the valid length a reference to > \item[VIRTIO_CAN_F_CAN_CLASSIC (0)] and \item[VIRTIO_CAN_F_CAN_FD (1)] > might be added. [virtio mailing lists are supposedly down for migration right now, I hope there's some kind of backfill happening later...] If the question comes up, it does make sense to add a clarification... as the virtio-can spec is already voted upon and merged, we'd need a patch on top. Not sure if it would qualify as an editorial update or a vote would be needed, best to see it first :) --------------------------------------------------------------------- To unsubscribe, e-mail: virtio-dev-unsubscribe@lists.oasis-open.org For additional commands, e-mail: virtio-dev-help@lists.oasis-open.org