netdev - Re: [PATCH v2 2/4] can: fixed-transceiver: Add documentation for CAN fixed transceiver bindings

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <b6ee18fa-a72b-9596-00d8-f6bd4a993293@hartkopp.net>
Date:   Fri, 28 Jul 2017 10:41:40 +0200
From:   Oliver Hartkopp <socketcan@...tkopp.net>
To:     Franklin S Cooper Jr <fcooper@...com>,
        Andrew Lunn <andrew@...n.ch>, linux-kernel@...r.kernel.org,
        devicetree@...r.kernel.org, netdev@...r.kernel.org,
        linux-can@...r.kernel.org, wg@...ndegger.com, mkl@...gutronix.de,
        robh+dt@...nel.org, quentin.schulz@...e-electrons.com,
        sergei.shtylyov@...entembedded.com
Subject: Re: [PATCH v2 2/4] can: fixed-transceiver: Add documentation for CAN
 fixed transceiver bindings

On 07/28/2017 06:57 AM, Kurt Van Dijck wrote:

> So while _a_ transceiver may be spec'd to 1MBit during arbitration,
> CAN FD packets may IMHO exceed that speed during data phase.

When the bitrate is limited to 1Mbit/s you are ONLY allowed to use 
1Mbit/s in the data section too (either with CAN or CAN FD).

> That was the whole point of CAN FD: exceed the limits required for
> correct arbitration on transceiver & wire.

No. CAN FD is about a different frame format with up to 64 bytes AND the 
possibility to increase the bitrate in the data section of the frame.

> So I do not agree on the single bandwidth limitation.

The transceiver provides a single maximum bandwidth. It's an ISO Layer 1 
device.

> The word 'max-arbitration-bitrate' makes the difference very clear.

I think you are mixing up ISO layer 1 and ISO layer 2.

Regards,
Oliver