netdev - Re: [PATCH 5/7] CAN: Add virtual CAN netdevice driver

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Message-ID: <46F0C128.70601@hartkopp.net>
Date:	Wed, 19 Sep 2007 08:26:48 +0200
From:	Oliver Hartkopp <oliver@...tkopp.net>
To:	Urs Thuermann <urs@...ogud.escape.de>
CC:	Patrick McHardy <kaber@...sh.net>, netdev@...r.kernel.org,
	David Miller <davem@...emloft.net>,
	Thomas Gleixner <tglx@...utronix.de>,
	Oliver Hartkopp <oliver.hartkopp@...kswagen.de>
Subject: Re: [PATCH 5/7] CAN: Add virtual CAN netdevice driver

Urs Thuermann wrote:
> Now I think we should consider removing the loopback code from
> can_send() and demand from each CAN driver that it *has to* implement
> this itself.
>   

I also thought about this solution, which would remove the 'loopback'
parameter in vcan.c and some loopback code in can_send().

My only concern was, that this would break with standard netdev
behaviour just to send and receive data to/from the medium.
To break with the standard behaviour might be ok here as the PF_CAN only
deals with CAN netdevs (ARPHRD_CAN) which can be seen as some closed
eco-system. But i don't know what should happen, if someone in the
future gets the idea to route CAN-frames over ethernet devices for any
reason? In this case we would have to touch every driver we'd like to
support.

IMO it makes more sense to let the 9 lines of loopback fallback code in
can_send() than to remove it.

Oliver

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