netdev - Re: [net 3/3] can: isotp: add SF_BROADCAST support for functional addressing

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Date:   Sat, 5 Dec 2020 12:26:44 +0100
From:   Oliver Hartkopp <socketcan@...tkopp.net>
To:     Jakub Kicinski <kuba@...nel.org>,
        Marc Kleine-Budde <mkl@...gutronix.de>
Cc:     netdev@...r.kernel.org, davem@...emloft.net,
        linux-can@...r.kernel.org, kernel@...gutronix.de,
        Thomas Wagner <thwa1@....de>
Subject: Re: [net 3/3] can: isotp: add SF_BROADCAST support for functional
 addressing



On 05.12.20 04:44, Jakub Kicinski wrote:
> On Fri,  4 Dec 2020 14:35:08 +0100 Marc Kleine-Budde wrote:
>> From: Oliver Hartkopp <socketcan@...tkopp.net>
>>
>> When CAN_ISOTP_SF_BROADCAST is set in the CAN_ISOTP_OPTS flags the CAN_ISOTP
>> socket is switched into functional addressing mode, where only single frame
>> (SF) protocol data units can be send on the specified CAN interface and the
>> given tp.tx_id after bind().
>>
>> In opposite to normal and extended addressing this socket does not register a
>> CAN-ID for reception which would be needed for a 1-to-1 ISOTP connection with a
>> segmented bi-directional data transfer.
>>
>> Sending SFs on this socket is therefore a TX-only 'broadcast' operation.
> 
> Unclear from this patch what is getting fixed. Looks a little bit like
> a feature which could be added in a backward compatible way, no?
> Is it only added for completeness of the ISOTP implementation?
> 

Yes, the latter.

It's a very small and simple tested addition and I hope it can still go 
into the initial upstream process.

Many thanks,
Oliver