From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Miller Subject: Re: softmac mtu Date: Sat, 23 Sep 2006 15:23:38 -0700 (PDT) Message-ID: <20060923.152338.74560339.davem@davemloft.net> References: <4515A9BF.90709@lwfinger.net> <20060923.144757.78710420.davem@davemloft.net> <4515AE54.4040403@lwfinger.net> Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit Cc: castet.matthieu@free.fr, netdev@vger.kernel.org Return-path: Received: from dsl027-180-168.sfo1.dsl.speakeasy.net ([216.27.180.168]:30649 "EHLO sunset.davemloft.net") by vger.kernel.org with ESMTP id S1750718AbWIWWXj (ORCPT ); Sat, 23 Sep 2006 18:23:39 -0400 To: Larry.Finger@lwfinger.net In-Reply-To: <4515AE54.4040403@lwfinger.net> Sender: netdev-owner@vger.kernel.org List-Id: netdev.vger.kernel.org From: Larry Finger Date: Sat, 23 Sep 2006 16:59:48 -0500 > Where/how does the device allow it? When I tried 'ifconfig eth0 mtu > 2000' on my VIA Technologies, Inc. VT6102 [Rhine-II] wired > controller, I got a 'SIOCSIFMTU: Invalid argument' message, which is > the same message I get on my BCM4306 wireless card. It allows it in the device specific ->change_mtu() method. Tigon3, for example, overrides this with it's own function called tg3_change_mtu() which checks if the particular model of the chip supports jumbo MTU and if so allows such a setting. The VIA driver simply doesn't override that function, and uses the default ethernet one because either that ethernet chip doesn't support the larger MTU or the author simply hasn't gotten around to implementing the override.