Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759641AbYABU6s (ORCPT ); Wed, 2 Jan 2008 15:58:48 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754314AbYABU6j (ORCPT ); Wed, 2 Jan 2008 15:58:39 -0500 Received: from iolanthe.rowland.org ([192.131.102.54]:56947 "HELO iolanthe.rowland.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1753528AbYABU6j (ORCPT ); Wed, 2 Jan 2008 15:58:39 -0500 Date: Wed, 2 Jan 2008 15:58:38 -0500 (EST) From: Alan Stern X-X-Sender: stern@iolanthe.rowland.org To: David Brownell cc: Mike Frysinger , , , Robin Getz , Subject: Re: [linux-usb-devel] [PATCH] : Allow embedded developers USB options normally reserved for OTG In-Reply-To: <200801021225.28370.david-b@pacbell.net> 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: 1376 Lines: 32 On Wed, 2 Jan 2008, David Brownell wrote: > On Wednesday 02 January 2008, Alan Stern wrote: > > On Wed, 2 Jan 2008, Mike Frysinger wrote: > > > > > perhaps the code size is arguable as to whether it really matters. > > > the reason we want it is that we have a USB host controller that will > > > not work with USB hubs, so we want to make sure the system does not > > > attempt such things. (yes, such a USB host controller is retarded, > > > but the decision was out of our hands.) > > > > Just out of curiosity, how does a host controller manage to avoid > > working with external hubs? > > The transaction translators in external high speed hubs require > hosts to issue particular USB transactions. If the host controller > doesn't implement the that split transaction support, then it won't > be supporting external hubs. So in theory one could connect a high-speed hub to such a host controller and expect it to communicate with high-speed devices. So long as no full- or low-speed devices are added there wouldn't be any split transactions. It wouldn't be USB-2.0 compliant but it should still work. 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/