From mboxrd@z Thu Jan 1 00:00:00 1970 From: Wolfgang Grandegger Subject: Re: [PATCH] Add Support for Freescale FlexCAN CAN controller Date: Mon, 27 Jul 2009 14:12:11 +0200 Message-ID: <4A6D999B.9010607@grandegger.com> 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> <4A6D86F5.7030707@hartkopp.net> 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: Oliver Hartkopp Return-path: Received: from mail-out.m-online.net ([212.18.0.10]:41331 "EHLO mail-out.m-online.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752429AbZG0MMO (ORCPT ); Mon, 27 Jul 2009 08:12:14 -0400 In-Reply-To: <4A6D86F5.7030707@hartkopp.net> Sender: netdev-owner@vger.kernel.org List-ID: Oliver Hartkopp wrote: > 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 ... Yep. Wolfgang.