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 mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id C40D8C433FE for ; Mon, 15 Nov 2021 14:37:23 +0000 (UTC) Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 7100560F51 for ; Mon, 15 Nov 2021 14:37:23 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org 7100560F51 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=ffwll.ch Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=lists.freedesktop.org Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 7E86D6EAC7; Mon, 15 Nov 2021 14:37:22 +0000 (UTC) Received: from mail-ed1-x535.google.com (mail-ed1-x535.google.com [IPv6:2a00:1450:4864:20::535]) by gabe.freedesktop.org (Postfix) with ESMTPS id B24156EAC7 for ; Mon, 15 Nov 2021 14:37:20 +0000 (UTC) Received: by mail-ed1-x535.google.com with SMTP id m20so27070216edc.5 for ; Mon, 15 Nov 2021 06:37:20 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ffwll.ch; s=google; h=date:from:to:cc:subject:message-id:mail-followup-to:references :mime-version:content-disposition:in-reply-to; bh=XiioWyqrq1D1dF9ZTugSJzsFvT/FPXCXiHcWrTggW1A=; b=FLdgxwJMdDUlwR0XKZUGvkuM2MNDSQ4GskVPXHQWieDno5xyhAkQ/RY6avWmujJ9BR OjFK/wuJ5u0TGea1y4NcILj+0ZBLckYJFooRvADUDIPpG12CBSoYlD1JXYloPbk/zK4c OX1wlFQSE1qbbROjeihgOQJAJ/lfWJLFcbRGw= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:date:from:to:cc:subject:message-id :mail-followup-to:references:mime-version:content-disposition :in-reply-to; bh=XiioWyqrq1D1dF9ZTugSJzsFvT/FPXCXiHcWrTggW1A=; b=mJwH89OhGhJDsIEOCygy5FJGlbKRH1G7fCIe0eKa9eXmithUPsjgXarikQfgQkZDNf aLhvlSbqCLzcQOqLpPQ5JJlMKR3k3B5ojY52GjR7YW1UjL6rYVF0f20ABIvMQFFe6FS9 BJQzgaMMUzm2n4sUzXcasGX/T6iCSGb7v2uo+SjsODW489muBxTvc1/dMHAHWeenrOK+ tWEfm1UkJV/aQK9gW7ezr7yxgnJns55Mc7ghCFmhHub8ZZIEqD8CZ/PkHVywFOFtCUfa AujApa/rJktBHpukEDWvYtQpeVLY+2NNJXJxL11WYoXWWnEYwqhGX0RNzIcRujCLOReH /UBg== X-Gm-Message-State: AOAM530LWEDSVAgn+vxwKjI5iAhiCMGRvZU1juu5ZZpSHBQTiJiOHjB3 yFLFbAlvetdIKdSEVtWKnwJ30W54Z/3MBA== X-Google-Smtp-Source: ABdhPJxXT/JTqH/P5/5MlVaHqEvS+WUgUgsUsgOfhK+nTHEXsPIZlCeVRsLARxXY95P+DTZWZPXr6g== X-Received: by 2002:aa7:c155:: with SMTP id r21mr21275479edp.124.1636987039311; Mon, 15 Nov 2021 06:37:19 -0800 (PST) Received: from phenom.ffwll.local ([2a02:168:57f4:0:efd0:b9e5:5ae6:c2fa]) by smtp.gmail.com with ESMTPSA id kw10sm6507786ejc.71.2021.11.15.06.37.18 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 15 Nov 2021 06:37:18 -0800 (PST) Date: Mon, 15 Nov 2021 15:37:16 +0100 From: Daniel Vetter To: Paul Cercueil Subject: Re: [PATCH 00/15] iio: buffer-dma: write() and new DMABUF based API Message-ID: Mail-Followup-To: Paul Cercueil , Jonathan Cameron , Michael Hennerich , linux-iio@vger.kernel.org, linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org, Christian =?iso-8859-1?Q?K=F6nig?= , linaro-mm-sig@lists.linaro.org, Alexandru Ardelean , linux-media@vger.kernel.org References: <20211115141925.60164-1-paul@crapouillou.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20211115141925.60164-1-paul@crapouillou.net> X-Operating-System: Linux phenom 5.10.0-8-amd64 X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Michael Hennerich , linux-iio@vger.kernel.org, linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org, linaro-mm-sig@lists.linaro.org, Alexandru Ardelean , Christian =?iso-8859-1?Q?K=F6nig?= , Jonathan Cameron , linux-media@vger.kernel.org Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" On Mon, Nov 15, 2021 at 02:19:10PM +0000, Paul Cercueil wrote: > Hi Jonathan, > > This patchset introduces a new userspace interface based on DMABUF > objects, to complement the existing fileio based API. > > The advantage of this DMABUF based interface vs. the fileio > interface, is that it avoids an extra copy of the data between the > kernel and userspace. This is particularly userful for high-speed > devices which produce several megabytes or even gigabytes of data per > second. > > The first few patches [01/15] to [03/15] are not really related, but > allow to reduce the size of the patches that introduce the new API. > > Patch [04/15] to [06/15] enables write() support to the buffer-dma > implementation of the buffer API, to continue the work done by > Mihail Chindris. > > Patches [07/15] to [12/15] introduce the new DMABUF based API. > > Patches [13/15] and [14/15] add support for cyclic buffers, only through > the new API. A cyclic buffer will be repeated on the output until the > buffer is disabled. > > Patch [15/15] adds documentation about the new API. > > For now, the API allows you to alloc DMABUF objects and mmap() them to > read or write the samples. It does not yet allow to import DMABUFs > parented to other subsystems, but that should eventually be possible > once it's wired. > > This patchset is inspired by the "mmap interface" that was previously > submitted by Alexandru Ardelean and Lars-Peter Clausen, so it would be > great if I could get a review from you guys. Alexandru's commit was > signed with his @analog.com address but he doesn't work at ADI anymore, > so I believe I'll need him to sign with a new email. Why dma-buf? dma-buf looks like something super generic and useful, until you realize that there's a metric ton of gpu/accelerator bagage piled in. So unless buffer sharing with a gpu/video/accel/whatever device is the goal here, and it's just for a convenient way to get at buffer handles, this doesn't sound like a good idea. Also if the idea is to this with gpus/accelerators then I'd really like to see the full thing, since most likely at that point you also want dma_fence. And once we talk dma_fence things get truly horrible from a locking pov :-( Or well, just highly constrained and I get to review what iio is doing with these buffers to make sure it all fits. Cheers, Daniel > > Cheers, > -Paul > > Alexandru Ardelean (1): > iio: buffer-dma: split iio_dma_buffer_fileio_free() function > > Paul Cercueil (14): > iio: buffer-dma: Get rid of incoming/outgoing queues > iio: buffer-dma: Remove unused iio_buffer_block struct > iio: buffer-dma: Use round_down() instead of rounddown() > iio: buffer-dma: Enable buffer write support > iio: buffer-dmaengine: Support specifying buffer direction > iio: buffer-dmaengine: Enable write support > iio: core: Add new DMABUF interface infrastructure > iio: buffer-dma: Use DMABUFs instead of custom solution > iio: buffer-dma: Implement new DMABUF based userspace API > iio: buffer-dma: Boost performance using write-combine cache setting > iio: buffer-dmaengine: Support new DMABUF based userspace API > iio: core: Add support for cyclic buffers > iio: buffer-dmaengine: Add support for cyclic buffers > Documentation: iio: Document high-speed DMABUF based API > > Documentation/driver-api/dma-buf.rst | 2 + > Documentation/iio/dmabuf_api.rst | 94 +++ > Documentation/iio/index.rst | 2 + > drivers/iio/adc/adi-axi-adc.c | 3 +- > drivers/iio/buffer/industrialio-buffer-dma.c | 670 ++++++++++++++---- > .../buffer/industrialio-buffer-dmaengine.c | 42 +- > drivers/iio/industrialio-buffer.c | 49 ++ > include/linux/iio/buffer-dma.h | 43 +- > include/linux/iio/buffer-dmaengine.h | 5 +- > include/linux/iio/buffer_impl.h | 8 + > include/uapi/linux/iio/buffer.h | 30 + > 11 files changed, 783 insertions(+), 165 deletions(-) > create mode 100644 Documentation/iio/dmabuf_api.rst > > -- > 2.33.0 > -- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch