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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 18673C00144 for ; Fri, 29 Jul 2022 16:47:11 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238207AbiG2QrJ (ORCPT ); Fri, 29 Jul 2022 12:47:09 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37888 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S238206AbiG2Qqy (ORCPT ); Fri, 29 Jul 2022 12:46:54 -0400 Received: from mga03.intel.com (mga03.intel.com [134.134.136.65]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 7B4C689AA9 for ; Fri, 29 Jul 2022 09:46:49 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1659113209; x=1690649209; h=message-id:date:mime-version:subject:to:cc:references: from:in-reply-to:content-transfer-encoding; bh=9jM9mztwAIfVEKsgETMmbLznTItKcbywHJIDqBixobk=; b=hAsuST5M0HjRr6DApr/KPaSY4QnErblvLhag+WnjTsWz4B/fI2KapGtg bvuJRWUHNRT/oahoIIYsInEb3bHAzReqF8K5fGZxeXwsv7tboYPCrD1Jf FhhyIw2sLwUtNopNjtMbvNYIUHYv5dcrHEjV23/IIDsUnUVLIlqT1IanP NrTXwGA+lt+cuWF3btbH36xeH1lkLwRGpPUjH7o1zaIIK7GHKLlHQoyD7 kNYLa1uB6gt+t0KASTUOstbv8pqsLuYKDtgqV5KzFU/8Xskm+ENroDL1M fqUxsIRp2tmzTFTC5vcz8yWklXoE28nAvn/CB/t10hYEtlLxk9DjB0+Wd w==; X-IronPort-AV: E=McAfee;i="6400,9594,10423"; a="290005899" X-IronPort-AV: E=Sophos;i="5.93,201,1654585200"; d="scan'208";a="290005899" Received: from fmsmga007.fm.intel.com ([10.253.24.52]) by orsmga103.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 29 Jul 2022 09:46:48 -0700 X-IronPort-AV: E=Sophos;i="5.93,201,1654585200"; d="scan'208";a="605014348" Received: from kaholo-mobl.amr.corp.intel.com (HELO [10.212.97.86]) ([10.212.97.86]) by fmsmga007-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 29 Jul 2022 09:46:47 -0700 Message-ID: <701aa1ba-9b25-51eb-8bd7-2389b501d79c@linux.intel.com> Date: Fri, 29 Jul 2022 11:46:32 -0500 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Firefox/91.0 Thunderbird/91.11.0 Subject: Re: [PATCH 2/5] soundwire: sysfs: cleanup the logic for creating the dp0 sysfs attributes Content-Language: en-US To: Greg Kroah-Hartman Cc: Vinod Koul , alsa-devel@alsa-project.org, Bard Liao , linux-kernel@vger.kernel.org, Sanyog Kale References: <20220729135041.2285908-1-gregkh@linuxfoundation.org> <20220729135041.2285908-2-gregkh@linuxfoundation.org> <9365e038-2146-98f8-f989-02827f221c34@linux.intel.com> <5caffe2a-f5a6-e312-a564-5fe29c4e2323@linux.intel.com> From: Pierre-Louis Bossart In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org >>>>> That should be fine, tools should just be looking for the attributes, >>>>> not the existance of a directory, right? >>>> >>>> The idea what that we would only expose ports that actually exist. >>>> That's helpful information anyone with a basic knowledge of the >>>> SoundWire specification would understand. >>> >>> Is "dp0" a port? If so, why isn't it a real device? >> >> The SoundWire spec defines the concept of 'data port'. The valid ranges >> are 1..14, but in all existing devices the number of data ports is way >> smaller, typically 2 to 4. Data ports (DPn) are source or sink, and >> there's no firm rule that data ports needs to be contiguous. >> >> DP0 is a 'special case' where the data transport is used for control >> information, e.g. programming large set of registers or firmware >> download. DP0 is completely optional in hardware, and not handled in >> Linux for now. >> >> DP0 and DPn expose low-level transport registers, which define how the >> contents of a FIFO will be written or read from the bus. Think of it as >> a generalization of the concept of TDM slots, where instead of having a >> fixed slot per frame the slot position/repetition/runlength can be >> programmed. >> >> The data ports could be as simple as 1-bit PDM, or support 8ch PCM >> 24-bits. That's the sort of information reported in attributes. > > Why not make them a real device like we do for USB endpoints? I don't see what adding another layer of hierarchy would bring. In their simplest configuration, there are 6 registers 8-bit exposed. And the port registers, when present, are accessed with a plain vanilla offset. > What uses these sysfs files today that would be confused about an empty > directory? That's a good question. I am not aware of any tools making use of those attributes. To a large degree, they are helpful only for debug and support, all these read-only attributes could be moved to debugfs. That could be a way to simplify everyone's life....