Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759200AbYFWPMX (ORCPT ); Mon, 23 Jun 2008 11:12:23 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755304AbYFWPMP (ORCPT ); Mon, 23 Jun 2008 11:12:15 -0400 Received: from iolanthe.rowland.org ([192.131.102.54]:54112 "HELO iolanthe.rowland.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1755238AbYFWPMO (ORCPT ); Mon, 23 Jun 2008 11:12:14 -0400 Date: Mon, 23 Jun 2008 11:12:13 -0400 (EDT) From: Alan Stern X-X-Sender: stern@iolanthe.rowland.org To: David Vrabel cc: Kernel development list , AntonioLin , , "Perez-Gonzalez, Inaky" Subject: Re: Scatter-gather list constraints In-Reply-To: <485FB730.2010705@csr.com> 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: 1114 Lines: 26 On Mon, 23 Jun 2008, David Vrabel wrote: > Note that this 1024 byte multiple is for one particular WUSB mass > storage device. The WUSB standard permits max packet sizes of up 3584 > (in multiples of 512), but I suspect WUSB mass storage devices will only > use 512, 1024, or 2048. > > For a solution, we may be able to do something if the HWA host > controller is passed a single URB with an s-g list (rather than one URB > per s-g list entry) and was careful about how it segmented the URB into > transfers to the rpipe. That would be ideal. However there is no way to pass an S-G list along with an URB; there's no field for it in the data structure. And none of the existing host controller drivers support such a thing. I suppose we could add a field to struct urb and add a flag indicating whether the controller driver supports S-G lists. 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/