From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754323AbZHKMsP (ORCPT ); Tue, 11 Aug 2009 08:48:15 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754144AbZHKMsO (ORCPT ); Tue, 11 Aug 2009 08:48:14 -0400 Received: from exprod5og107.obsmtp.com ([64.18.0.184]:36863 "EHLO exprod5og107.obsmtp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752204AbZHKMsL (ORCPT ); Tue, 11 Aug 2009 08:48:11 -0400 Message-ID: <4A8125AC.30400@gefanuc.com> Date: Tue, 11 Aug 2009 09:02:52 +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> <4A804D67.4080308@gefanuc.com> <20090810195048.GB3055@braap.org> In-Reply-To: <20090810195048.GB3055@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: > Martyn Welch wrote: > >> 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". >> > > Again, he (the driver writer) should know *nothing* about that. > > As for the scatter-gather case, what should happen is: > > User: hey, there's a buffer I want to transfer. here's > a pointer and size > Buffer where? On VME or PCI, where are you transferring it to? The API I have will allow scattered locations on VME to be copied to PCI and visa-versa, scattered locations on PCI to be copied to VME and visa-versa. Even scattered locations on VME to scattered locations on PCI with a bit of effort. > VME layer: ok, passing it to the bridge > VME bridge: I know I'm over PCI, so I'll get the pages > from memory and map the sg list over PCI, and > then will tell the bridge to perform from there. > > That's just a particular example, but for the user (read driver > writer) it's much simpler this way. Doesn't need to know about > lists or whatever. > But seems to fail to provide the flexibility that I outlined above. Martyn > E. > -- 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