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 2A8AFC00144 for ; Fri, 29 Jul 2022 17:25:46 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237705AbiG2RZk (ORCPT ); Fri, 29 Jul 2022 13:25:40 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:43168 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232888AbiG2RZi (ORCPT ); Fri, 29 Jul 2022 13:25:38 -0400 Received: from mga06.intel.com (mga06b.intel.com [134.134.136.31]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 4E3646050B for ; Fri, 29 Jul 2022 10:25:37 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1659115537; x=1690651537; h=message-id:date:mime-version:subject:to:cc:references: from:in-reply-to:content-transfer-encoding; bh=vj9Gd3F0ZFA+lxnvVFnGuGBsXg4J6Y0l+pUnAC5iJsg=; b=CZHAIUqU7Dc71LAM+ADhhRAHs6cLJwB40a1KJ/AFak+FILoN2YumzUa5 nQbKMUGi9hLDgfzByXJnZl7AG9NKOp4lyyJCxsZpUbImPRn4p5mM0Ph+/ HbNGoslpSZj1VViWaJWQmHC4vReQzAhMBfSkwwbrP4TmQ12TS9s5+2eJk rY+JWIRYEDq9rQ9ZaYGdkLlV28amebI+JXlUUqWqYJPvsfDRqSAsBtOlK OYox+Q4cDWY6U3QypvcaDOxAdwlwStQAXqR/7Gb5wcoQEi/an3aQS7uAE eC4CXr3/SwghC4MaL/TbqK9bnTk5WahzBMAeLa8+qsj7c0F6frIaFZm2h w==; X-IronPort-AV: E=McAfee;i="6400,9594,10423"; a="350517423" X-IronPort-AV: E=Sophos;i="5.93,201,1654585200"; d="scan'208";a="350517423" Received: from fmsmga007.fm.intel.com ([10.253.24.52]) by orsmga104.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 29 Jul 2022 10:25:36 -0700 X-IronPort-AV: E=Sophos;i="5.93,201,1654585200"; d="scan'208";a="605026163" 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 10:25:35 -0700 Message-ID: Date: Fri, 29 Jul 2022 12:25:34 -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> <701aa1ba-9b25-51eb-8bd7-2389b501d79c@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 On 7/29/22 12:15, Greg Kroah-Hartman wrote: > On Fri, Jul 29, 2022 at 11:46:32AM -0500, Pierre-Louis Bossart wrote: >> >>>>>>> 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. > > Who uses these registers? The bus layer. When a 'stream' is created, the 'bit allocation' will define who owns which bitSlots in the frame and the registers will be programmed. The bit allocation may be dynamic or fixed depending on the host. >>> 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.... > > That would be much nicer, put it all in a single debugfs file and it > would be so simple. > > What attributes could we do that for? All of them really - except maybe the device number which could be used to figure what the device is when looking at power status and other 'standard' sysfs attributes. sdw:3:025d:0714:01 is not really user-friendly, device_number 1 is.