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=-3.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=no 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 47A97C433FF for ; Thu, 1 Aug 2019 17:51:27 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 237F5206A2 for ; Thu, 1 Aug 2019 17:51:27 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2387829AbfHARv0 (ORCPT ); Thu, 1 Aug 2019 13:51:26 -0400 Received: from smtprelay0094.hostedemail.com ([216.40.44.94]:40995 "EHLO smtprelay.hostedemail.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1727899AbfHARvZ (ORCPT ); Thu, 1 Aug 2019 13:51:25 -0400 Received: from filter.hostedemail.com (clb03-v110.bra.tucows.net [216.40.38.60]) by smtprelay05.hostedemail.com (Postfix) with ESMTP id A41C018029123; Thu, 1 Aug 2019 17:51:24 +0000 (UTC) X-Session-Marker: 6A6F6540706572636865732E636F6D X-HE-Tag: club18_80939144a8607 X-Filterd-Recvd-Size: 3545 Received: from XPS-9350 (cpe-23-242-196-136.socal.res.rr.com [23.242.196.136]) (Authenticated sender: joe@perches.com) by omf06.hostedemail.com (Postfix) with ESMTPA; Thu, 1 Aug 2019 17:51:23 +0000 (UTC) Message-ID: Subject: Re: [PATCH 08/12] printk: Replace strncmp with str_has_prefix From: Joe Perches To: Chuhong Yuan Cc: Petr Mladek , Sergey Senozhatsky , Steven Rostedt , LKML Date: Thu, 01 Aug 2019 10:51:22 -0700 In-Reply-To: References: <20190729151505.9660-1-hslester96@gmail.com> <5dee05d6cb8498b3e636f5e8a62da673334cb5a9.camel@perches.com> Content-Type: text/plain; charset="UTF-8" User-Agent: Evolution 3.30.5-0ubuntu0.18.10.1 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 2019-08-01 at 23:23 +0800, Chuhong Yuan wrote: > Joe Perches 于2019年7月30日周二 上午8:16写道： > > On Mon, 2019-07-29 at 23:15 +0800, Chuhong Yuan wrote: > > > strncmp(str, const, len) is error-prone. > > > We had better use newly introduced > > > str_has_prefix() instead of it. > > [] > > > diff --git a/kernel/printk/braille.c b/kernel/printk/braille.c > > [] > > > @@ -11,10 +11,10 @@ > > > > > > int _braille_console_setup(char **str, char **brl_options) > > > { > > > - if (!strncmp(*str, "brl,", 4)) { > > > + if (str_has_prefix(*str, "brl,")) { > > > *brl_options = ""; > > > *str += 4; > > > - } else if (!strncmp(*str, "brl=", 4)) { > > > + } else if (str_has_prefix(*str, "brl=")) { > > > *brl_options = *str + 4; > > > > Better to get rid of the += 4 uses too by storing the result > > of str_has_prefix and using that as the addend. > > > > Perhaps > > size_t len; > > > > if ((len = str_has_prefix(*str, "brl,"))) { > > *brl_options = ""; > > *str += len; > > } else if ((len = str_has_prefix(*str, "brl="))) { > > etc... > > > > I find that checkpatch.pl forbids assignment in if condition. > So this seems to be infeasible... So the code could be rewritten like below: (though it's trivial as-is) --- kernel/printk/braille.c | 30 ++++++++++++++++++++---------- 1 file changed, 20 insertions(+), 10 deletions(-) diff --git a/kernel/printk/braille.c b/kernel/printk/braille.c index 1d21ebacfdb8..46dd9fcc7525 100644 --- a/kernel/printk/braille.c +++ b/kernel/printk/braille.c @@ -11,19 +11,29 @@ int _braille_console_setup(char **str, char **brl_options) { - if (!strncmp(*str, "brl,", 4)) { + size_t len; + + len = str_has_prefix(*str, "brl,"); + if (len) { *brl_options = ""; - *str += 4; - } else if (!strncmp(*str, "brl=", 4)) { - *brl_options = *str + 4; - *str = strchr(*brl_options, ','); - if (!*str) { - pr_err("need port name after brl=\n"); - return -EINVAL; - } - *((*str)++) = 0; + *str += len; + return 0; + } + + len = str_has_prefix(*str, "brl="); + if (!len) + return 0; + + *brl_options = *str + len; + + *str = strchr(*brl_options, ','); + if (!*str) { + pr_err("need port name after brl=\n"); + return -EINVAL; } + *((*str)++) = 0; + return 0; }