From mboxrd@z Thu Jan 1 00:00:00 1970 From: James Bottomley Subject: Re: [PATCH] [3/22] Remove unchecked_isa_dma in advansys.c Date: Tue, 26 Feb 2008 07:18:18 -0800 Message-ID: <1204039098.3254.63.camel@localhost.localdomain> References: <200802251235.889863872@firstfloor.org> <20080224233516.0657F1B4183@basil.firstfloor.org> <20080225214746.GA11382@parisc-linux.org> <20080225224035.GB21577@one.firstfloor.org> <20080225225022.GD20273@parisc-linux.org> <20080226034402.GD21577@one.firstfloor.org> Mime-Version: 1.0 Content-Type: text/plain Content-Transfer-Encoding: 7bit Return-path: Received: from accolon.hansenpartnership.com ([76.243.235.52]:40747 "EHLO accolon.hansenpartnership.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1760767AbYBZPSY (ORCPT ); Tue, 26 Feb 2008 10:18:24 -0500 In-Reply-To: <20080226034402.GD21577@one.firstfloor.org> Sender: linux-scsi-owner@vger.kernel.org List-Id: linux-scsi@vger.kernel.org To: Andi Kleen Cc: Matthew Wilcox , linux-scsi@vger.kernel.org On Tue, 2008-02-26 at 04:44 +0100, Andi Kleen wrote: > On Mon, Feb 25, 2008 at 03:50:22PM -0700, Matthew Wilcox wrote: > > On Mon, Feb 25, 2008 at 11:40:35PM +0100, Andi Kleen wrote: > > > > (I must have fixed it somehow because it works on parisc, which is most > > > > unforgiving of drivers which do DMA without the DMA API). > > > > > > At least on x86 the DMA API cannot do ISA bouncing. > > > > You're saying that if I set a 24-bit DMA mask, and then do a > > pci_alloc_coherent(), x86 might hand me back something that's not > > accessible? That would be just broken. > > No pci_alloc_coherent works, but pci_map_* will not. Yes, it does ... dma_map is a flush/virt_to_phys on x86. so of course it works. If you mean it doesn't transform from > 24 bit phys to < 24 bit phys, then yes; but that's not an API requirement; that's what bounce buffering is all about, so for ISA devices we always only call dma_map on < 24 bit phys addresses and it all works. James