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=-2.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 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 A13F4C433DF for ; Tue, 19 May 2020 17:54:57 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7BC1B20674 for ; Tue, 19 May 2020 17:54:57 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727009AbgESRy4 (ORCPT ); Tue, 19 May 2020 13:54:56 -0400 Received: from mga01.intel.com ([192.55.52.88]:45549 "EHLO mga01.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726059AbgESRy4 (ORCPT ); Tue, 19 May 2020 13:54:56 -0400 IronPort-SDR: Q43gCF6nAzm+KczJ8J8u3FB2Z1E14Btw9dTRv3+LSIsfrF0Ppw4XdNGCyHP2vyKmW2Xywhe0uX SzHX4OB1djvA== X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga005.jf.intel.com ([10.7.209.41]) by fmsmga101.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 19 May 2020 10:54:54 -0700 IronPort-SDR: hpPnUjjcjcPumfqHPKVthzvzlEuENKNnPVgsTW0wCgzE3FsftI1zpMToUV9TUSRC9AinDR/6dS tFZ1ILxHWeow== X-IronPort-AV: E=Sophos;i="5.73,410,1583222400"; d="scan'208";a="439705633" Received: from rchatre-mobl.amr.corp.intel.com (HELO [10.255.229.46]) ([10.255.229.46]) by orsmga005-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 19 May 2020 10:54:53 -0700 Subject: Re: [PATCH V5 4/4] x86/resctrl: Use appropriate API for strings terminated by newline To: Andy Shevchenko Cc: Thomas Gleixner , Fenghua Yu , Borislav Petkov , Tony Luck , kuo-lang.tseng@intel.com, ravi.v.shankar@intel.com, Ingo Molnar , Babu Moger , "H. Peter Anvin" , "maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" , Linux Kernel Mailing List References: <4a9603b8-32fb-024a-e2f5-14e95b4e3763@intel.com> <20200519160710.GK1634618@smile.fi.intel.com> From: Reinette Chatre Message-ID: <87d00e95-7944-2fa4-fd02-1662ec4382fe@intel.com> Date: Tue, 19 May 2020 10:54:52 -0700 User-Agent: Mozilla/5.0 (Windows NT 6.3; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.8.0 MIME-Version: 1.0 In-Reply-To: <20200519160710.GK1634618@smile.fi.intel.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Andy, On 5/19/2020 9:07 AM, Andy Shevchenko wrote: > On Tue, May 19, 2020 at 08:50:22AM -0700, Reinette Chatre wrote: >> On 5/19/2020 1:28 AM, Andy Shevchenko wrote: >>> On Tue, May 19, 2020 at 2:50 AM Reinette Chatre >>> wrote: > > ... > >>>> + ret = sysfs_match_string(rdt_mode_str, buf); >>>> + if (ret < 0) { >>>> + rdt_last_cmd_puts("Unknown or unsupported mode\n"); >>>> + ret = -EINVAL; >>>> + goto out; >>>> + } >> >> From your previous email ... >> >>>> + ret = sysfs_match_string(rdt_mode_str, buf); >>>> + if (ret < 0) { >>>> + rdt_last_cmd_puts("Unknown or unsupported mode\n"); >>> >>>> + ret = -EINVAL; >>> >>> This is redundant. >> >> I understand that shadowing an error code is generally of concern. In >> this case the error code is set to -EINVAL to ensure that it is the same >> error code that was returned to user space originally and will continue >> to be so no matter what changes may come to sysfs_match_string(). > > It returns -EINVAL and if that will be ever changed this driver would be one of > hundreds who suffers. Not if we keep this change ... but that is no longer of concern with the removal of the check as you propose later. > > ... > >>> Can't we unify latter with a former like ... > >> This would have been ideal if done from the start but currently "0" is >> returned if the current mode is pseudo-locked and user attempts to >> change the mode to pseudo-locked. Thus, to maintain the current user >> interface the check if user wants to set pseudo-locked mode is moved >> after the check if new mode is same as existing mode and thus not >> unified because that will result in an error returned always when user >> requests pseudo-locked mode. > > Ah, I see now. > > But we can then drop the check from sysfs_match_string() returned value, like > > user_m = sysfs_match_string(); > if (...) { > ... > } else { // w/o even checking for the PSEUDO_LOCKED > ... > goto out; > } > > Can we? > Yes, we can. Will do. Reinette