From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755716AbZHJQjx (ORCPT ); Mon, 10 Aug 2009 12:39:53 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755512AbZHJQjw (ORCPT ); Mon, 10 Aug 2009 12:39:52 -0400 Received: from exprod5og104.obsmtp.com ([64.18.0.178]:57507 "EHLO exprod5og104.obsmtp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755317AbZHJQjw (ORCPT ); Mon, 10 Aug 2009 12:39:52 -0400 Message-ID: <4A804D67.4080308@gefanuc.com> Date: Mon, 10 Aug 2009 17:40:07 +0100 From: Martyn Welch User-Agent: Thunderbird 2.0.0.22 (X11/20090608) MIME-Version: 1.0 To: "Emilio G. Cota" CC: Greg K-H , linux-kernel@vger.kernel.org, devel@driverdev.osuosl.org, Sebastien Dugue Subject: Re: [patch 1/5] Staging: VME Framework for the Linux Kernel References: <20090803205657.964064732@mini.kroah.org> <20090803210111.GB28430@kroah.com> <20090808230145.GB27151@braap.org> <4A801644.2070009@gefanuc.com> <20090810141442.GA18456@braap.org> <20090810153127.GB23319@braap.org> In-Reply-To: <20090810153127.GB23319@braap.org> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Emilio G. Cota wrote: > Emilio G. Cota wrote: > >> I've had a closer look; it seems to me that most of it is unnecessary; >> there's no show those lists to a driver. I'd just provide a single >> 'do_dma(attributes)' call that sleeps until it's done (or similar). >> > > s/there's no show/there's no point in showing/ > > Basically the driver simply shouldn't care about these DMA > lists. It just wants to get the work done, no matter how. > > E. > I have provided helper functions to aid with filling out structures that define the attributes, these are then pointed to by a generic DMA transfer structure. Bar the helper functions to aid in completing these commonly filled structures, at this level I can't see much difference. However rather than targeting a the "single shot" operation of the DMA controller I have provided the ability for the driver writer to use the link-list mode. If the driver writer wants a "single shot" effect, there's little overhead in creating a one item link-list and executing it. However, without support for this mode the author is stuck with single shot transfers. If the author wants to perform scatter gather type transfers, without this functionality in the API - which is supported by all the bridges I have seen - he won't be able to easily avail himself of this functionality and get "work done". Martyn -- Martyn Welch MEng MPhil MIET (Principal Software Engineer) T:+44(0)1327322748 GE Fanuc Intelligent Platforms Ltd, |Registered in England and Wales Tove Valley Business Park, Towcester, |(3828642) at 100 Barbirolli Square, Northants, NN12 6PF, UK T:+44(0)1327359444 |Manchester,M2 3AB VAT:GB 927559189