Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S265785AbUFSDuY (ORCPT ); Fri, 18 Jun 2004 23:50:24 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S265809AbUFSDuY (ORCPT ); Fri, 18 Jun 2004 23:50:24 -0400 Received: from stat1.steeleye.com ([65.114.3.130]:58283 "EHLO hancock.sc.steeleye.com") by vger.kernel.org with ESMTP id S265785AbUFSDuK (ORCPT ); Fri, 18 Jun 2004 23:50:10 -0400 Subject: Re: DMA API issues From: James Bottomley To: Ian Molton Cc: david-b@pacbell.net, Linux Kernel , greg@kroah.com, tony@atomide.com, jamey.hicks@hp.com, joshua@joshuawise.com In-Reply-To: <20040619011416.64d16c4e.spyro@f2s.com> References: <1087582845.1752.107.camel@mulgrave> <20040618193544.48b88771.spyro@f2s.com> <1087584769.2134.119.camel@mulgrave> <20040618195721.0cf43ec2.spyro@f2s.com> <40D34078.5060909@pacbell.net> <20040618204438.35278560.spyro@f2s.com> <1087588627.2134.155.camel@mulgrave> <20040619002522.0c0d8e51.spyro@f2s.com> <1087601363.2078.208.camel@mulgrave> <20040619005106.15b8c393.spyro@f2s.com> <1087603453.2135.224.camel@mulgrave> <20040619011416.64d16c4e.spyro@f2s.com> Content-Type: text/plain Content-Transfer-Encoding: 7bit X-Mailer: Ximian Evolution 1.0.8 (1.0.8-9) Date: 18 Jun 2004 22:49:49 -0500 Message-Id: <1087616990.2078.240.camel@mulgrave> Mime-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1150 Lines: 33 On Fri, 2004-06-18 at 19:14, Ian Molton wrote: > On 18 Jun 2004 19:04:11 -0500 > James Bottomley wrote: > > > Because the piece of memory you wish to access is bus remote. > > No, its *not* > > my CPU can write there directly. > > no strings attached. > > the DMA API just only understands how to map from RAM, not anything > else. I think you'll actually find that it is. OHCI is a device (representing a USB hub), it's attached to the system by some interface that constitutes a bus (the bus interface transforming the CPU access cycles to device access cycles, translating interrupts etc.). But even if you've somehow managed to glue an OHCI directly on to the system memory controller, from the point of view of the DMA API, the memory the device contains is still bus remote. To be useful, the API has to deal with bus remote memory in all its forms. James - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/