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=-1.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 786B1C433DF for ; Sun, 21 Jun 2020 07:25:06 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 579322485F for ; Sun, 21 Jun 2020 07:25:06 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1592724306; bh=O+HtJYaaPHUMFJE4t1nnQ2MuJq56zD7rjTetemmt5lM=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=aV/qIkvgLu5cp3RTnWfYIFbSMo5FMBqHF99AUrV0n++Asyu8PnPFC9zRSB4CH9Io7 oJf7okVt0UAymY59DzgBkwGJbA47FtxlkjWD9vDKXq3yaXKCAepspVQlcQzDvD1Zgh r68hhrHUadKjrQGzsBH7QANSrJCEfHo2O+ZAfzTg= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729439AbgFUHZF (ORCPT ); Sun, 21 Jun 2020 03:25:05 -0400 Received: from mail.kernel.org ([198.145.29.99]:33400 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729410AbgFUHZC (ORCPT ); Sun, 21 Jun 2020 03:25:02 -0400 Received: from localhost (unknown [171.61.66.58]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 81CF724861; Sun, 21 Jun 2020 07:25:01 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1592724302; bh=O+HtJYaaPHUMFJE4t1nnQ2MuJq56zD7rjTetemmt5lM=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=unppcI2Q4B6j3eqWu1fxtJn6mxib5JV88n8S/w4kYFhB91e+KoQgufAF8fYFoQQkd RETm3PEbbTdzQI8VfTSirlfGcaXH4kpaHzrAqmM8DHjaZLVCt4qmn0s0a80ejOWAIe MbJwa3BZrkhyI/8HjGnjVKmKWntVRLEWAsiIlwjo= Date: Sun, 21 Jun 2020 12:54:57 +0530 From: Vinod Koul To: Dave Jiang Cc: Federico Vaga , Dan Williams , dmaengine@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: DMA Engine: Transfer From Userspace Message-ID: <20200621072457.GA2324254@vkoul-mobl> References: <5614531.lOV4Wx5bFT@harkonnen> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 19-06-20, 16:31, Dave Jiang wrote: > > > On 6/19/2020 3:47 PM, Federico Vaga wrote: > > Hello, > > > > is there the possibility of using a DMA engine channel from userspace? > > > > Something like: > > - configure DMA using ioctl() (or whatever configuration mechanism) > > - read() or write() to trigger the transfer > > > > I may have supposedly promised Vinod to look into possibly providing > something like this in the future. But I have not gotten around to do that > yet. Currently, no such support. And I do still have serious reservations about this topic :) Opening up userspace access to DMA does not sound very great from security point of view. Federico, what use case do you have in mind? We should keep in mind dmaengine is an in-kernel interface providing services to various subsystems, so you go thru the respective subsystem kernel interface (network, display, spi, audio etc..) which would in turn use dmaengine. -- ~Vinod