From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754016AbYIXTRS (ORCPT ); Wed, 24 Sep 2008 15:17:18 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752116AbYIXTQ7 (ORCPT ); Wed, 24 Sep 2008 15:16:59 -0400 Received: from h155.mvista.com ([63.81.120.155]:4899 "EHLO imap.sh.mvista.com" rhost-flags-OK-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S1752095AbYIXTQ6 (ORCPT ); Wed, 24 Sep 2008 15:16:58 -0400 Message-ID: <48DA9263.5060103@ru.mvista.com> Date: Wed, 24 Sep 2008 23:17:55 +0400 From: Sergei Shtylyov Organization: MontaVista Software Inc. User-Agent: Mozilla/5.0 (X11; U; Linux i686; rv:1.7.2) Gecko/20040803 X-Accept-Language: ru, en-us, en-gb MIME-Version: 1.0 To: David Brownell Cc: avorontsov@ru.mvista.com, Andrew Morton , greg@kroah.com, linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org, linuxppc-dev@ozlabs.org, leoli@freescale.com, timur@freescale.com Subject: Re: [PATCH 3/3] USB: driver for Freescale QUICC Engine USB Host Controller References: <20080918151659.GA20140@oksana.dev.rtsoft.ru> <20080923225730.GB13617@oksana.dev.rtsoft.ru> <48DA1544.5010307@ru.mvista.com> <200809241159.04427.david-b@pacbell.net> In-Reply-To: <200809241159.04427.david-b@pacbell.net> Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello. David Brownell wrote: >>>> ... then the root hub emulation is completely pointless. >>>It isn't. We always should emulate the root hub. The root hub >>>is part and parcel of any USB Host. Even the one-port one. >> Hm, maybe that's what USB core thinks (because UHCI/OHCI/EHCI all >>have it) but e.g. MUSB doesn't have the root hub registers... > Only the OHCI registers have bit positions matching what the USB > spec says for hub status bits. Oh, didn't know that. > Everything else, including musb_hdrc, has the relevant status encoded in other bits. Yes, but I thought that if there are no multiple ports, having the hub is just pointless. >>I looked at the core and figured that USB core seems to use the root hub >>interface for port PM, etc. and expects it to bee present, so it seems >>unavoidable indeed... :-/ > Or more fundamentally: for enumeration. "Unavoidable" is correct. ;) Not sure what you mean here but I guess having a root hub alows an uniform model of controlling the ports... anyway, USB specifies that it must be present in the host. WBR, Sergei