From mboxrd@z Thu Jan 1 00:00:00 1970 From: Maxime Bizon Subject: Re: alignment faults in 3.6 Date: Thu, 11 Oct 2012 13:47:35 +0200 Message-ID: <1349956055.1232.9.camel@sakura.staff.proxad.net> References: <20121005082439.GF4625@n2100.arm.linux.org.uk> <506ED18C.3010009@gmail.com> <20121005140556.GQ4625@n2100.arm.linux.org.uk> <506EEFBB.3060705@gmail.com> <507619FA.6080001@jonmasters.org> <1349949638.21172.8445.camel@edumazet-glaptop> <1349950926.21172.8521.camel@edumazet-glaptop> <20121011103257.GO4625@n2100.arm.linux.org.uk> <1349952574.21172.8604.camel@edumazet-glaptop> <1349952970.1232.5.camel@sakura.staff.proxad.net> <1349954899.21172.8728.camel@edumazet-glaptop> Reply-To: mbizon@freebox.fr Mime-Version: 1.0 Content-Type: text/plain; charset="ANSI_X3.4-1968" Content-Transfer-Encoding: 7bit Cc: =?ISO-8859-1?Q?M=E5ns_Rullg=E5rd?= , Russell King - ARM Linux , netdev@vger.kernel.org, David Laight , Jon Masters , linux-arm-kernel@lists.infradead.org To: Eric Dumazet Return-path: Received: from ns.iliad.fr ([212.27.33.1]:46523 "EHLO ns.iliad.fr" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754578Ab2JKLrh (ORCPT ); Thu, 11 Oct 2012 07:47:37 -0400 In-Reply-To: <1349954899.21172.8728.camel@edumazet-glaptop> Sender: netdev-owner@vger.kernel.org List-ID: On Thu, 2012-10-11 at 13:28 +0200, Eric Dumazet wrote: > You probably are aware that a driver can use : > > - a fragment to hold the frame given by the hardware, with whatever > alignment is needed by the hardware. > > Then allocate an skb with enough room (128 bytes) to pull the headers as > needed later. > > skb = netdev_alloc_skb_ip_align(dev, 128); What happen at tx time, supposing that same hardware cannot do SG ? Aren't we going to memcpy the data into the head ? -- Maxime