From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Thu, 12 Sep 2002 02:12:21 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Thu, 12 Sep 2002 02:12:21 -0400 Received: from dp.samba.org ([66.70.73.150]:54953 "EHLO lists.samba.org") by vger.kernel.org with ESMTP id ; Thu, 12 Sep 2002 02:12:20 -0400 From: Paul Mackerras MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Message-ID: <15744.12392.868240.502920@argo.ozlabs.ibm.com> Date: Thu, 12 Sep 2002 16:12:56 +1000 (EST) To: Jens Axboe Cc: benh@kernel.crashing.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] highmem I/O for ide-pmac.c In-Reply-To: <20020911130209.GL1089@suse.de> References: <15743.15275.412038.388540@argo.ozlabs.ibm.com> <20020911130209.GL1089@suse.de> X-Mailer: VM 6.75 under Emacs 20.7.2 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Jens Axboe writes: > Doesn't look like it's needed at all, at least you never turn on highmem > I/O with ide_toggle_bounce() :-) Foo, neither I do. :( > BTW, it would be ok to export that from ide-dma.c instead of duplicating > it in ide-pmac. Looking at it again, both ide_build_sglist and ide_raw_build_sglist do *almost* what we want. If ide-pmac used hwif->sg_table instead of pmif->sg_table, and if ide_[raw_]build_sglist were exported and took the maximum number of entries as a parameter instead of using the PRD_ENTRIES constant, then ide-pmac wouldn't need to have its own versions of those routines. Would those changes be OK? Ben, any reason why we have to use pmif->sg_table rather than hwif->sg_table? > Also, can you grow sg segments indefinitely? Each DBDMA (descriptor-based DMA) command has a 16-byte length field, so is limited to 65535 bytes. There is code in pmac_ide_build_dmatable to create multiple DBDMA commands from a single scatterlist element if necessary. We should limit the lengths of the segments instead, then we could have a 1-1 correspondence of scatterlist elements to DBDMA command blocks. Paul.