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 E094DC49EA6 for ; Thu, 24 Jun 2021 14:24:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C7A126024A for ; Thu, 24 Jun 2021 14:24:35 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231873AbhFXO0x (ORCPT ); Thu, 24 Jun 2021 10:26:53 -0400 Received: from mga06.intel.com ([134.134.136.31]:63560 "EHLO mga06.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231169AbhFXO0x (ORCPT ); Thu, 24 Jun 2021 10:26:53 -0400 IronPort-SDR: sx3gDlPaGyxQVXu5wl5Wg9ljHfvZ4YjhouzZQsw3/n+QR2OjBAiiPYHDyWYxyxyDzrXcl6sbWv ZCjPIPXZOr8Q== X-IronPort-AV: E=McAfee;i="6200,9189,10024"; a="268610469" X-IronPort-AV: E=Sophos;i="5.83,296,1616482800"; d="scan'208";a="268610469" Received: from orsmga006.jf.intel.com ([10.7.209.51]) by orsmga104.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 24 Jun 2021 07:24:32 -0700 IronPort-SDR: BOnw6q+YprfzkrA2H+5wpuIJTQg4qNnIwCFqowTlQr/HHbE5TZVmu34xNxggsbicRGF9FCF+mj hNgl81uOb/hg== X-IronPort-AV: E=Sophos;i="5.83,296,1616482800"; d="scan'208";a="406658358" Received: from akleen-mobl1.amr.corp.intel.com (HELO [10.209.74.185]) ([10.209.74.185]) by orsmga006-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 24 Jun 2021 07:24:32 -0700 Subject: Re: [PATCH 2/7] perf: Create a symlink for a PMU To: Greg KH , kan.liang@linux.intel.com Cc: 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> From: Andi Kleen Message-ID: Date: Thu, 24 Jun 2021 07:24:31 -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 > But first off, why is this symlink suddenly needed? What is so special > about this new hardware that it breaks the existing model? The driver can be in two modes: - Driver fully knows the hardware and puts in the correct Linux names - Driver doesn't know the hardware but is in a fallback mode where it only looks at a discovery table. There we don't have the correct names, just an numeric identifier for the different hardware sub components. In the later mode the numeric identifier is used in sysfs, in the former case the full Linux name. But we want to keep some degree of Linux user space compatibility between the two, that is why the full mode creates a symlink from the "numeric" name. This way the (ugly) identifiers needed for the fallback mode work everywhere. -Andi