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=-5.5 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 2F775C433E1 for ; Tue, 14 Jul 2020 16:49:15 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 1552A22571 for ; Tue, 14 Jul 2020 16:49:15 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728087AbgGNQtO (ORCPT ); Tue, 14 Jul 2020 12:49:14 -0400 Received: from mga07.intel.com ([134.134.136.100]:24475 "EHLO mga07.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726062AbgGNQtO (ORCPT ); Tue, 14 Jul 2020 12:49:14 -0400 IronPort-SDR: sG6FR9LDdBAh9OFAZbydWojuVPv7uSudemPznpiYhU/zXx/PO4KyYptqLgrE2rHEnP2mgLwH33 uDmIjofcdWuQ== X-IronPort-AV: E=McAfee;i="6000,8403,9681"; a="213748140" X-IronPort-AV: E=Sophos;i="5.75,352,1589266800"; d="scan'208";a="213748140" X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga004.fm.intel.com ([10.253.24.48]) by orsmga105.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 14 Jul 2020 09:49:13 -0700 IronPort-SDR: 43WJZfLT0kjZUqlt8ocOMEylSo7SumVMqMI+Ur3jhEQ0x0Y3UBB1QpGj1WRuq+4bxI2fLMDprb Ztv5v9RASv+A== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.75,352,1589266800"; d="scan'208";a="307939488" Received: from djiang5-mobl1.amr.corp.intel.com (HELO [10.209.140.223]) ([10.209.140.223]) by fmsmga004.fm.intel.com with ESMTP; 14 Jul 2020 09:49:12 -0700 Subject: Re: [PATCH v7 05/11] dmaengine: Introduce DMA-device device_caps callback To: Serge Semin Cc: Vinod Koul , Andy Shevchenko , Viresh Kumar , Dan Williams , Alexey Malahov , Thomas Bogendoerfer , Arnd Bergmann , Rob Herring , linux-mips@vger.kernel.org, devicetree@vger.kernel.org, dmaengine@vger.kernel.org, linux-kernel@vger.kernel.org References: <20200709224550.15539-1-Sergey.Semin@baikalelectronics.ru> <20200709224550.15539-6-Sergey.Semin@baikalelectronics.ru> <20200710084503.GE3703480@smile.fi.intel.com> <20200710093834.su3nsjesnhntpd6d@mobilestation> <07d4a977-1de6-b611-3d4f-7c7d6cd7fe5f@intel.com> <20200714160830.GL34333@vkoul-mobl> <20200714162953.2333hke6pfvovjuk@mobilestation> From: Dave Jiang Message-ID: <7d1a9ae9-0a95-cba5-be62-4493501039e7@intel.com> Date: Tue, 14 Jul 2020 09:49:12 -0700 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: <20200714162953.2333hke6pfvovjuk@mobilestation> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: dmaengine-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: dmaengine@vger.kernel.org On 7/14/2020 9:29 AM, Serge Semin wrote: > On Tue, Jul 14, 2020 at 09:18:16AM -0700, Dave Jiang wrote: >> >> >> On 7/14/2020 9:08 AM, Vinod Koul wrote: >>> On 13-07-20, 13:55, Dave Jiang wrote: >>>> >>>> >>>> On 7/10/2020 2:38 AM, Serge Semin wrote: >>>>> On Fri, Jul 10, 2020 at 11:45:03AM +0300, Andy Shevchenko wrote: >>>>>> On Fri, Jul 10, 2020 at 01:45:44AM +0300, Serge Semin wrote: >>>>>>> There are DMA devices (like ours version of Synopsys DW DMAC) which have >>>>>>> DMA capabilities non-uniformly redistributed between the device channels. >>>>>>> In order to provide a way of exposing the channel-specific parameters to >>>>>>> the DMA engine consumers, we introduce a new DMA-device callback. In case >>>>>>> if provided it gets called from the dma_get_slave_caps() method and is >>>>>>> able to override the generic DMA-device capabilities. >>>>>> >>>>> >>>>>> In light of recent developments consider not to add 'slave' and a such words to the kernel. >>>>> >>>>> As long as the 'slave' word is used in the name of the dma_slave_caps >>>>> structure and in the rest of the DMA-engine subsystem, it will be ambiguous >>>>> to use some else terminology. If renaming needs to be done, then it should be >>>>> done synchronously for the whole subsystem. >>>> >>>> What about just calling it dma_device_caps? Consider this is a useful >>>> function not only slave DMA will utilize this. I can see this being useful >>>> for some of my future code with idxd driver. >>> >>> Some of the caps may make sense to generic dmaengine but few of them do >>> not :) While at it, am planning to make it dmaengine_periph_caps to >>> denote that these are dmaengine peripheral capabilities. >>> >> > >> If the function only passes in periph_caps, how do we allow the non periph >> DMA utilize this function? > > Hello Dave. That seems reasonable. "dma_device_caps" or even "dma_chan_caps" > might be more suitable seeing after this patchset merged in the "dma_slave_caps" > may really provide the DMA channel-specific configs. Moreover that structure is > accessible only by means of the dma_chan descriptor: > > int dma_get_slave_caps(struct dma_chan *chan, struct dma_slave_caps *caps); > > which makes those caps being the channel-specific even without this patchset. > > So as I see it "dma_chan_caps" might be the better choice. Hi Sergey. Yes I think that sounds pretty good. Especially seeing there are DMA engines that have channels with different/asymmetric capabilities now. > > -Sergey >