netdev - Re: [RFC v3 5/6] j1939: rename NAME to UUID?

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Date:	Thu, 21 Apr 2011 08:54:45 +0200
From:	Kurt Van Dijck <kurt.van.dijck@....be>
To:	Oliver Hartkopp <socketcan@...tkopp.net>
Cc:	socketcan-core@...ts.berlios.de, netdev@...r.kernel.org
Subject: Re: [RFC v3 5/6] j1939: rename NAME to UUID?

> 
> Kurt, the problem for me is, that you constantly state that your approach is
> the best. For me it is not.
no userspace counterpart can handle transient conditions like kernel can...
> 
> The major issue in your implementation is the lack of the possibility to
> simulate several j1939 ECUs on one Linux host talking to each other via
> virtual CAN busses to create a complete j1939 network. And so far you did not
> address this request.
Oliver,
I tried to explain already several times that this stack _IS_ capable
of having several j1939 ECU's on one linux host, talking to any CAN bus, virtual
or physical.
I agree that if this was not the case, your arguments would have been valid.

The major improvement (IMHO) of my in-kernel j1939 stack is that several
applications can also contribute to the same ECU, without protocol violations.

side note: this is not even a matter introduced with address claiming :-0
> 

ever done this?
$ ip addr add 192.168.0.1/24 dev eth0
$ ip addr add 192.168.1.1/24 dev eth0

Likewise I do now:
$ ip addr add j1939 0x20 dev can0
$ ip addr add j1939 0x21 dev can0

I see no problem there.

With address claiming:
$ ip addr add j1939 name 0123456789ABCDE0 dev can0
$ ip addr add j1939 name 0123456789ABCDE1 dev can0
and my daemon to choose addresses (posted later today on can-utils)

$ jacd --range 0x20-0x30 0123456789ABCDE0 can0
$ jacd --range 0x20-0x30 0123456789ABCDE1 can0

No, no typos here. both ECU's will resolve conflicts on CAN, on the same host!
The second will ECU will finally get 0x21, _as should be_ per J1939.

Oliver,
The way I understand your request, this addressed that. What did I miss up to here?

I skipped a lot of your original email since the issue addressed here seems to
be source of misunderstanding.

Kind regards,
Kurt
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