Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760082AbYFKPRA (ORCPT ); Wed, 11 Jun 2008 11:17:00 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752478AbYFKPQv (ORCPT ); Wed, 11 Jun 2008 11:16:51 -0400 Received: from iolanthe.rowland.org ([192.131.102.54]:40714 "HELO iolanthe.rowland.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1751148AbYFKPQu (ORCPT ); Wed, 11 Jun 2008 11:16:50 -0400 Date: Wed, 11 Jun 2008 11:16:49 -0400 (EDT) From: Alan Stern X-X-Sender: stern@iolanthe.rowland.org To: Jens Axboe cc: AntonioLin , David Vrabel , USB list , Kernel development list Subject: Re: [S] Re: [linux-uwb] packet size problem In-Reply-To: <20080611145349.GD20851@kernel.dk> Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 998 Lines: 27 On Wed, 11 Jun 2008, Jens Axboe wrote: > > Jens, this is a question for you. How come we're getting an SG element > > whose lenth is 3584 when the request_queue's dma_alignment mask is set > > to 1023? Is dma_alignment not the right parameter to set? > > dma_alignment mask is the buffer address alignment, so they are not > completely the same. Well then, put it this way: We don't care particularly about the address alignment as such, but we do need the buffer length to be a multiple of 1024 for all but the last element in the SG list. Is there a better way to accomplish this? > But it does sound odd, since you would then be > spanning two pages for that sg element. Is this before or after dma > mapping the sg table? Both. Alan Stern -- 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/