Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Wed, 3 Oct 2001 18:44:49 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Wed, 3 Oct 2001 18:44:39 -0400 Received: from adsl-64-109-89-110.chicago.il.ameritech.net ([64.109.89.110]:33873 "EHLO localhost.localdomain") by vger.kernel.org with ESMTP id ; Wed, 3 Oct 2001 18:44:28 -0400 Message-Id: <200110032244.f93MiI103485@localhost.localdomain> X-Mailer: exmh version 2.2 06/23/2000 with nmh-1.0.4 To: Jes Sorensen cc: Linux Bigot , linux-kernel@vger.kernel.org Subject: Re: how to get virtual address from dma address Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Date: Wed, 03 Oct 2001 17:44:18 -0500 From: James Bottomley Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org > Linux> All programmers I am relatively new to linux kernel. Please > Linux> advise what is the safe way to get the original virtaul address > Linux> from dma address e.g., > You have to store the address you pass to pci_map_single() somewhere > in your data structures together with the dma address. Yes, but speaking as someone who had to use a large hammer to convert his driver from bus_to_virt et al., it does seem rather hard not to have the equivalent for the new pci_dma paradigm. It does present an obstacle persuading people to convert drivers, particularly if the hardware is going to present a linked list of addresses (as SCSI hardware often does). After all, whatever device maps between the io bus and the memory bus, it must always map a given dma_addr_t to a known physical address. It can't be that hard to provide an an API in the kernel which can compute this relationship (although I can see it may be expensive to walk iommu page tables). I'm only really asking for a dma_addr_t to virtual address by the way. I see that mapping the other way would be problematic. James Bottomley - 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/