From mboxrd@z Thu Jan 1 00:00:00 1970 From: Oliver Hartkopp Subject: Re: [PATCH] Add Support for Freescale FlexCAN CAN controller Date: Mon, 27 Jul 2009 12:52:37 +0200 Message-ID: <4A6D86F5.7030707@hartkopp.net> References: <20090724131933.GL2714@pengutronix.de> <4A69CB46.1090704@grandegger.com> <20090727062559.GP2714@pengutronix.de> <4A6D727B.7030304@grandegger.com> <4A6D76B7.8030105@hartkopp.net> <4A6D7C7E.9050703@grandegger.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: Socketcan-core@lists.berlios.de, Linux Netdev List To: Wolfgang Grandegger Return-path: Received: from mo-p00-ob.rzone.de ([81.169.146.162]:43864 "EHLO mo-p00-ob.rzone.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756032AbZG0Kwl (ORCPT ); Mon, 27 Jul 2009 06:52:41 -0400 In-Reply-To: <4A6D7C7E.9050703@grandegger.com> Sender: netdev-owner@vger.kernel.org List-ID: Wolfgang Grandegger wrote: > Oliver Hartkopp wrote: >> 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. > > I thought the user can toggle the IFF_ECHO flag with the "ip" utility, > but obviously I'm wrong. AFAIK the only driver that currently allows to switch this flag is the vcan driver - but this is for testing purposes only and can be configured by the module commandline. I assume having the echo functionality runtime configurable is only effort and complicates the driver ... Best regards, Oliver