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=-5.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE, SPF_PASS,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 8B916C2B9F4 for ; Fri, 25 Jun 2021 14:22:12 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6D87461939 for ; Fri, 25 Jun 2021 14:22:12 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231736AbhFYOYc (ORCPT ); Fri, 25 Jun 2021 10:24:32 -0400 Received: from mga12.intel.com ([192.55.52.136]:32450 "EHLO mga12.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230270AbhFYOYb (ORCPT ); Fri, 25 Jun 2021 10:24:31 -0400 IronPort-SDR: Up3nZCynybgOdz0y/5K/MzqSpaBnWIJWPGftGThoAM79or07JmFFmgt9VH0bTcletRWVD/WC38 Az0dyybJNXWg== X-IronPort-AV: E=McAfee;i="6200,9189,10026"; a="187366147" X-IronPort-AV: E=Sophos;i="5.83,299,1616482800"; d="scan'208";a="187366147" Received: from orsmga001.jf.intel.com ([10.7.209.18]) by fmsmga106.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 25 Jun 2021 07:22:10 -0700 IronPort-SDR: BsNR9vog7CvaxPMKyA/Yr4txTnlH7feyXLogq0BFq1uLiFi2fDbz8jt5lIsKmlv2jajTpyPZjM it/9TIObjQOw== X-IronPort-AV: E=Sophos;i="5.83,299,1616482800"; d="scan'208";a="488201668" Received: from akleen-mobl1.amr.corp.intel.com (HELO [10.209.62.195]) ([10.209.62.195]) by orsmga001-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 25 Jun 2021 07:22:09 -0700 Subject: Re: [PATCH 2/7] perf: Create a symlink for a PMU To: Greg KH Cc: kan.liang@linux.intel.com, peterz@infradead.org, mingo@redhat.com, linux-kernel@vger.kernel.org, eranian@google.com, namhyung@kernel.org, acme@kernel.org, jolsa@redhat.com References: <1624497729-158864-1-git-send-email-kan.liang@linux.intel.com> <1624497729-158864-3-git-send-email-kan.liang@linux.intel.com> <1e536604-cf93-0f09-401e-2073924c5582@linux.intel.com> <29d5f315-578f-103c-9523-ae890e29c7e7@linux.intel.com> From: Andi Kleen Message-ID: <540d8a38-da12-56c8-8306-8d3d61ae1d6b@linux.intel.com> Date: Fri, 25 Jun 2021 07:22:08 -0700 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.11.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Content-Language: en-US Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 6/24/2021 10:19 PM, Greg KH wrote: > On Thu, Jun 24, 2021 at 10:28:36AM -0700, Andi Kleen wrote: >>> But a driver does not caer. And if perf does not care, who cares? >> The users who write scripts that specify the perf events on the perf command >> line. > Great, then as you have deemed the device name part of your documented > api, then keep it stable as that is what you decided to do a long time > ago when it was created. The fully supported driver keeps it stable, but the driver in fallback mode (as in running on a yet unknown system) can't because it doesn't have enough information. It has to fall back to the numeric identifiers. Supporting yet unknown systems is a big advantage, missing full kernel support is the number one reason people can't use uncore monitoring today. The symlink keeps some degree of compatibility between the two. Anyways thinking about it if Greg doesn't want symlinks (even though sysfs already has symlinks elsewhere), maybe we could just create two devices without symlinks. Kan, do you think that would work? -Andi