From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752331AbZHJTu6 (ORCPT ); Mon, 10 Aug 2009 15:50:58 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751804AbZHJTu6 (ORCPT ); Mon, 10 Aug 2009 15:50:58 -0400 Received: from waldorf.bytemark.co.uk ([212.110.162.22]:35516 "EHLO waldorf.bytemark.co.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751331AbZHJTu5 (ORCPT ); Mon, 10 Aug 2009 15:50:57 -0400 Date: Mon, 10 Aug 2009 21:50:48 +0200 From: "Emilio G. Cota" To: Martyn Welch 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 Message-ID: <20090810195048.GB3055@braap.org> 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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4A804D67.4080308@gefanuc.com> User-Agent: Mutt/1.5.19 (2009-01-05) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 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. E.