Subject: Re: [PATCH] Add Support for Freescale FlexCAN CAN controller

From: Oliver Hartkopp <[email-masked]>
Date: Mon, 27 Jul 2009 11:43:19 +0200

Wolfgang Grandegger wrote:
> Sascha Hauer wrote:
>> On Fri, Jul 24, 2009 at 04:55:02PM +0200, Wolfgang Grandegger wrote:

> [...]
>>>> +	kfree_skb(skb);
>>> Support for echo skb using can_put/get_echo_skb() is missing. It should
>>> not be a big deal to add it.
>> In fact it's not missing, but the hardware is configured to receive its
>> own packets, so this isn't needed.
> 
> But the user may disable IFF_ECHO, which should be handled somehow.

Really?

IMO IFF_ECHO indicates the capability of the network driver to perform the MAC
layer frame echo on driver level.

Only when you have a CAN driver that does not have this capability (the 'bad'
non default case) this flag is cleared.

There is no need to provide a mode that can switch this functionality 'on' and
'off'. IFF_ECHO is just an indication provided by the driver.

When the FlexCAN controller can 'receive' a sent frame, so that it reflects
the correct message order on the bus, this is perfect.

In this case Sascha should set the IFF_ECHO flag and he's done.

Regards,
Oliver