Messages in this thread | | | Subject | Re: [PATCH v2 2/4] can: fixed-transceiver: Add documentation for CAN fixed transceiver bindings | From | Oliver Hartkopp <> | Date | Thu, 27 Jul 2017 20:47:37 +0200 |
| |
On 07/26/2017 08:29 PM, Franklin S Cooper Jr wrote: >
> I'm fine with switching to using bitrate instead of speed. Kurk was > originally the one that suggested to use the term arbitration and data > since thats how the spec refers to it. Which I do agree with. But your > right that in the drivers (struct can_priv) we just use bittiming and > data_bittiming (CAN-FD timings). I don't think adding "fd" into the > property name makes sense unless we are calling it something like > "max-canfd-bitrate" which I would agree is the easiest to understand. > > So what is the preference if we end up sticking with two properties? > Option 1 or 2? > > 1) > max-bitrate > max-data-bitrate > > 2) > max-bitrate > max-canfd-bitrate > >
1
>> A CAN transceiver is limited in bandwidth. But you only have one RX and >> one TX line between the CAN controller and the CAN transceiver. The >> transceiver does not know about CAN FD - it has just a physical(!) layer >> with a limited bandwidth. This is ONE limitation. >> >> So I tend to specify only ONE 'max-bitrate' property for the >> fixed-transceiver binding. >> >> The fact whether the CAN controller is CAN FD capable or not is provided >> by the netlink configuration interface for CAN controllers. > > Part of the reasoning to have two properties is to indicate that you > don't support CAN FD while limiting the "arbitration" bit rate.
??
It's a physical layer device which only has a bandwidth limitation. The transceiver does not know about CAN FD.
> With one > property you can not determine this and end up having to make some > assumptions that can quickly end up biting people.
Despite the fact that the transceiver does not know anything about ISO layer 2 (CAN/CAN FD) the properties should look like
max-bitrate canfd-capable
then.
But when the tranceiver is 'canfd-capable' agnostic, why provide a property for it?
Maybe I'm wrong but I still can't follow your argumentation ideas.
Regards, Oliver
| |