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=-8.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=unavailable 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 A0D4BC432C0 for ; Mon, 18 Nov 2019 08:47:25 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 8184420740 for ; Mon, 18 Nov 2019 08:47:25 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726708AbfKRIrY (ORCPT ); Mon, 18 Nov 2019 03:47:24 -0500 Received: from metis.ext.pengutronix.de ([85.220.165.71]:34679 "EHLO metis.ext.pengutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726631AbfKRIrX (ORCPT ); Mon, 18 Nov 2019 03:47:23 -0500 Received: from ptx.hi.pengutronix.de ([2001:67c:670:100:1d::c0]) by metis.ext.pengutronix.de with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.92) (envelope-from ) id 1iWcgo-0004FT-A3; Mon, 18 Nov 2019 09:47:18 +0100 Received: from ukl by ptx.hi.pengutronix.de with local (Exim 4.89) (envelope-from ) id 1iWcgn-0001PK-VT; Mon, 18 Nov 2019 09:47:17 +0100 Date: Mon, 18 Nov 2019 09:47:17 +0100 From: Uwe =?iso-8859-1?Q?Kleine-K=F6nig?= To: Dmitry Torokhov Cc: Wolfram Sang , linux-iio@vger.kernel.org, Luca Ceresoli , linux-i2c@vger.kernel.org, linux-kernel@vger.kernel.org, kernel@pengutronix.de Subject: Re: [PATCH v3 3/3] i2c: smbus: switch from loops to memcpy Message-ID: <20191118084717.rv2f24fg523gq6dr@pengutronix.de> References: <20191112203132.163306-1-dmitry.torokhov@gmail.com> <20191112203132.163306-4-dmitry.torokhov@gmail.com> <20191118074757.edyfvz5s3pqnu67y@pengutronix.de> <20191118080939.GC251795@dtor-ws> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20191118080939.GC251795@dtor-ws> User-Agent: NeoMutt/20170113 (1.7.2) X-SA-Exim-Connect-IP: 2001:67c:670:100:1d::c0 X-SA-Exim-Mail-From: ukl@pengutronix.de X-SA-Exim-Scanned: No (on metis.ext.pengutronix.de); SAEximRunCond expanded to false X-PTX-Original-Recipient: linux-kernel@vger.kernel.org Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Nov 18, 2019 at 12:09:39AM -0800, Dmitry Torokhov wrote: > On Mon, Nov 18, 2019 at 08:47:57AM +0100, Uwe Kleine-König wrote: > > Hello Dmitry, > > > > On Tue, Nov 12, 2019 at 12:31:32PM -0800, Dmitry Torokhov wrote: > > > When copying memory from one buffer to another, instead of open-coding > > > loops with byte-by-byte copies let's use memcpy() which might be a bit > > > faster and makes intent more clear. > > > > > > Signed-off-by: Dmitry Torokhov > > > > > > --- > > > > > > Changes in v3: > > > - new patch using memcpy() for moving data around > > > > > > drivers/i2c/i2c-core-smbus.c | 15 +++++---------- > > > 1 file changed, 5 insertions(+), 10 deletions(-) > > > > > > diff --git a/drivers/i2c/i2c-core-smbus.c b/drivers/i2c/i2c-core-smbus.c > > > index 7b4e2270eeda1..bbafdd3b1b114 100644 > > > --- a/drivers/i2c/i2c-core-smbus.c > > > +++ b/drivers/i2c/i2c-core-smbus.c > > > @@ -397,8 +397,7 @@ static s32 i2c_smbus_xfer_emulated(struct i2c_adapter *adapter, u16 addr, > > > } > > > > > > i2c_smbus_try_get_dmabuf(&msg[0], command); > > > - for (i = 1; i < msg[0].len; i++) > > > - msg[0].buf[i] = data->block[i - 1]; > > > + memcpy(msg[0].buf + 1, data->block, msg[0].len - 1); > > > > Can it happen that msg[0].len is zero? > > No, it can not, because of the "msg[0].len = data->block[0] + 2;" line > above. OK, and as passing data with data->block[0] = 254 also makes the code do strange things already without your patch. I now also checked the other conversions for similar problems and didn't find any. So: Acked-by: Uwe Kleine-König Best regards Uwe -- Pengutronix e.K. | Uwe Kleine-König | Industrial Linux Solutions | https://www.pengutronix.de/ |