From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mike Sinkovsky Subject: Re: [PATCH v4] Ethernet driver for the WIZnet W5300 chip Date: Wed, 28 Mar 2012 11:52:43 +0600 Message-ID: <4F72A72B.5020609@permonline.ru> References: <1332149037-12025-1-git-send-email-msink@permonline.ru><1332752876-1650-1-git-send-email-msink@permonline.ru> <20120327.223545.1996930432677091672.davem@davemloft.net> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: netdev@vger.kernel.org To: David Miller Return-path: Received: from mail4.ccl.ru ([195.222.140.73]:50657 "EHLO mail4.ccl.ru" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751195Ab2C1Fw4 (ORCPT ); Wed, 28 Mar 2012 01:52:56 -0400 In-Reply-To: <20120327.223545.1996930432677091672.davem@davemloft.net> Sender: netdev-owner@vger.kernel.org List-ID: 28.03.2012 8:35, David Miller wrote: >> +/* >> + * Frame size is hardwired to 1514 bytes (including header), >> + * => MTU for 802.1Q frames must be set to 1500-4 = 1496 >> + */ >> +#define W5300_HARD_MTU 1500 > > I've told you that you must set the VLAN challenged feature flag > (NETIF_F_VLAN_CHALLENGED) for devices which have this restriction. > > Just set that, and remove this comment, since the feature bit setting > documents this restriction fully and perfectly. From Documentation/netdev-features.txt: >NETIF_F_VLAN_CHALLENGED should be set for devices which can't cope with VLAN >headers. Some drivers set this because the cards can't handle the bigger MTU. >[FIXME: Those cases could be fixed in VLAN code by allowing only reduced-MTU >VLANs. This may be not useful, though.] My case is exactly what is here in FIXME comment - yes, this chip cannot handle full size MTU for VLANs, and TCP/IP traffic don't work well over this VLAN. But we actually use it for traffic where frame size is known to be less than 1500 - TDMoE to Asterisk in our case - and it works perfectly. So as ideal we'll like to disable TCP/IP over this sort of VLANs, but still enable TDMoE traffic. If it is possible. But if you want - ok, I'll disable VLAN support entirely for this chip in mainline version. (Now working on similar driver for W5100 chip, hopefully will post both soon.) -- Mike