From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 35276C00449 for ; Fri, 5 Oct 2018 21:24:15 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 043B1206B2 for ; Fri, 5 Oct 2018 21:24:15 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 043B1206B2 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=davemloft.net Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728631AbeJFEYp (ORCPT ); Sat, 6 Oct 2018 00:24:45 -0400 Received: from shards.monkeyblade.net ([23.128.96.9]:46536 "EHLO shards.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725896AbeJFEYp (ORCPT ); Sat, 6 Oct 2018 00:24:45 -0400 Received: from localhost (c-67-183-145-105.hsd1.wa.comcast.net [67.183.145.105]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (Client did not present a certificate) (Authenticated sender: davem-davemloft) by shards.monkeyblade.net (Postfix) with ESMTPSA id 8682413ADF961; Fri, 5 Oct 2018 14:24:12 -0700 (PDT) Date: Fri, 05 Oct 2018 14:24:12 -0700 (PDT) Message-Id: <20181005.142412.601607260441380535.davem@davemloft.net> To: ben.dooks@codethink.co.uk Cc: netdev@vger.kernel.org, David.Laight@ACULAB.COM, oneukum@suse.com, linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org, linux-kernel@lists.codethink.co.uk Subject: Re: [PATCH] usbnet: smsc95xx: simplify tx_fixup code From: David Miller In-Reply-To: <20181002165602.21033-1-ben.dooks@codethink.co.uk> References: <59988ed22559410881addfecf58335eb@AcuMS.aculab.com> <20181002165602.21033-1-ben.dooks@codethink.co.uk> X-Mailer: Mew version 6.7 on Emacs 26 / Mule 6.0 (HANACHIRUSATO) Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-Greylist: Sender succeeded SMTP AUTH, not delayed by milter-greylist-4.5.12 (shards.monkeyblade.net [149.20.54.216]); Fri, 05 Oct 2018 14:24:12 -0700 (PDT) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Ben Dooks Date: Tue, 2 Oct 2018 17:56:02 +0100 > - memcpy(skb->data, &tx_cmd_a, 4); > + ptr = skb_push(skb, 8); > + tx_cmd_a = cpu_to_le32(tx_cmd_a); > + tx_cmd_b = cpu_to_le32(tx_cmd_b); > + memcpy(ptr, &tx_cmd_a, 4); > + memcpy(ptr+4, &tx_cmd_b, 4); Even a memcpy() through a void pointer does not guarantee that gcc will not emit word sized loads and stores. You must use the get_unaligned()/put_unaligned() facilities to do this properly. I also agree that making a proper type and structure instead of using a void pointer would be better.