From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753722Ab1AJNw1 (ORCPT ); Mon, 10 Jan 2011 08:52:27 -0500 Received: from mail.digidescorp.com ([66.244.163.200]:22341 "EHLO mail.digidescorp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753420Ab1AJNwZ (ORCPT ); Mon, 10 Jan 2011 08:52:25 -0500 X-Greylist: delayed 454 seconds by postgrey-1.27 at vger.kernel.org; Mon, 10 Jan 2011 08:52:25 EST X-Spam-Processed: mail.digidescorp.com, Mon, 10 Jan 2011 07:44:50 -0600 X-Authenticated-Sender: steve@digidescorp.com X-Return-Path: prvs=19910c6f74=steve@digidescorp.com X-Envelope-From: steve@digidescorp.com X-MDaemon-Deliver-To: linux-kernel@vger.kernel.org Subject: Re: CPU Initiated DMA From: "Steven J. Magnani" To: Robert Hancock Cc: linux-kernel@vger.kernel.org In-Reply-To: <4D28A9EF.3050400@gmail.com> References: <87mxncv3ge.fsf@inspiron.ap.columbia.edu> <4D28A9EF.3050400@gmail.com> Content-Type: text/plain; charset="UTF-8" Date: Mon, 10 Jan 2011 07:44:45 -0600 Message-ID: <1294667085.3139.3.camel@iscandar.digidescorp.com> Mime-Version: 1.0 X-Mailer: Evolution 2.32.1 (2.32.1-1.fc14) Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, 2011-01-08 at 12:16 -0600, Robert Hancock wrote: > On 01/07/2011 02:55 PM, Nikolaus Rath wrote: > > Hello, > > > > I want to write a driver for a rather dumb PCI card, which cannot become > > bus master itself. Is it possible to use a DMA controller on the > > mainboard to still transfer data to the card without occupying the CPU? > > > > (I believe this is the way DMA used to work on ISA cards, but do recent > > x86 systems still have a DMA controller for the CPU?) > > The legacy ISA DMA controller worked like that, but you can't use that > with PCI devices. Essentially there is no way to do this, barring > perhaps some wierd platform specific feature. I believe a DMA Engine would work here - platform-specific, yes, but I wouldn't call it "wierd" :) See Documentation/dmaengine.txt. Regards, ------------------------------------------------------------------------ Steven J. Magnani "I claim this network for MARS! www.digidescorp.com Earthling, return my space modulator!" #include