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=-8.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=ham 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 11CFCC43461 for ; Wed, 9 Sep 2020 17:01:38 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D65FC21919 for ; Wed, 9 Sep 2020 17:01:37 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730695AbgIIRBe (ORCPT ); Wed, 9 Sep 2020 13:01:34 -0400 Received: from mga14.intel.com ([192.55.52.115]:42301 "EHLO mga14.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731255AbgIIRBH (ORCPT ); Wed, 9 Sep 2020 13:01:07 -0400 IronPort-SDR: bHno9ZgnHJF7A5usV6zlKzWavmLmaJjnf133iDWCMZGZi7SAMEiDivWmTbolxeDsMq78ZHKAOu D7L1NO5jVqqg== X-IronPort-AV: E=McAfee;i="6000,8403,9739"; a="157652638" X-IronPort-AV: E=Sophos;i="5.76,409,1592895600"; d="scan'208";a="157652638" X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga005.fm.intel.com ([10.253.24.32]) by fmsmga103.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 09 Sep 2020 10:01:01 -0700 IronPort-SDR: /N/heFDKxKb2HFDk4yR30nCvJc4feNSfGOv8JktzCfqUo5uUbej66lwTOSnK38lIgTO2iLeICJ sITk8ooDxFwQ== X-IronPort-AV: E=Sophos;i="5.76,409,1592895600"; d="scan'208";a="505516346" Received: from rsetyawa-mobl1.amr.corp.intel.com (HELO [10.212.20.145]) ([10.212.20.145]) by fmsmga005-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 09 Sep 2020 10:01:00 -0700 Subject: Re: [PATCH] soundwire: bus: add enumerated slave to device list To: Srinivas Kandagatla , vkoul@kernel.org, yung-chuan.liao@linux.intel.com Cc: sanyog.r.kale@intel.com, alsa-devel@alsa-project.org, linux-kernel@vger.kernel.org References: <20200909082711.11670-1-srinivas.kandagatla@linaro.org> <80081c70-9137-c9f0-9813-8166275ef7af@linux.intel.com> <4cdcda10-bdc6-211f-d279-e74f57684b79@linux.intel.com> From: Pierre-Louis Bossart Message-ID: Date: Wed, 9 Sep 2020 12:00:57 -0500 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 9/9/20 10:54 AM, Srinivas Kandagatla wrote: > > > On 09/09/2020 15:39, Pierre-Louis Bossart wrote: >> >>>>> Currently slave devices are only added either from device tree or acpi >>>>> entries. However lets say, there is wrong or no entry of a slave >>>>> device >>>>> in DT that is enumerated, then there is no way for user to know all >>>>> the enumerated devices on the bus. >>>> >>>> Sorry Srinivas, I don't understand your point. >>>> >>>> The sysfs entries will include all devices that are described in >>>> platform firmware (be it DT or ACPI). >>> >>> yes that is true, but it will not include all the enumerated devices >>> on the bus! >>> >>> In my case on a new board I was trying to figure out what devices are >>> on the bus even before even adding any device tree entries! >> >> We've seen this before but dynamic debug provides all the information >> you need. see e.g. the logs from >> https://sof-ci.01.org/linuxpr/PR2425/build4447/devicetest/ >> >> jf-cml-rvp-sdw-1 kernel: [  289.751974] soundwire sdw-master-0: Slave >> attached, programming device number >> jf-cml-rvp-sdw-1 kernel: [  289.752121] soundwire sdw-master-0: SDW >> Slave Addr: 10025d070000 <<< HERE > > Yes, I have noticed this too! This will be printed for every call to > sdw_extract_slave_id()! > > ... >> >> Now I get your point but >> a) you already have a dynamic debug trace to list all devices >> b) adding 'undeclared' devices would make things quite murky and is >> only half of the solution. We already struggle because we already have >> 'ghost' devices in sysfs that are not physically present, and no way >> to differentiate between the two. If we did add those entries, then >> we'd need two new sysfs attributes such as >> 'declared' and 'enumerated'. > > I totally agree with you on dealing with the undeclared devices, which > is unnecessary mess! It's not necessarily that bad. - if the intent is to have a single platform firmware that can deal with different boards, it's a good thing. - but if it's just sloppy platform firmware that just does copy-paste from platform to platform then indeed it becomes a mess. > May be we could make the enumerated devices discovery bit more verbose! Maybe adding a device number sysfs entry would help, e.g. reporting NotAttched or a value in [0,11] would tell you if the device is actually present.