Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1030721Ab1EWVGo (ORCPT ); Mon, 23 May 2011 17:06:44 -0400 Received: from na3sys009aog108.obsmtp.com ([74.125.149.199]:46086 "EHLO na3sys009aog108.obsmtp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1030683Ab1EWVGh convert rfc822-to-8bit (ORCPT ); Mon, 23 May 2011 17:06:37 -0400 Subject: Re: [PATCH v12 7/8] usb: Adding SuperSpeed support to dummy_hcd Mime-Version: 1.0 (Apple Message framework v1084) Content-Type: text/plain; charset=us-ascii From: Felipe Balbi In-Reply-To: Date: Tue, 24 May 2011 00:06:29 +0300 Cc: Felipe Balbi , Sarah Sharp , Tanya Brokhman , , , , , "'open list'" Content-Transfer-Encoding: 8BIT Message-Id: References: To: Alan Stern X-Mailer: Apple Mail (2.1084) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2235 Lines: 56 Hi, (replying from another PC, not sure if formatting will be broken, hopefully not) On May 23, 2011, at 7:28 PM, Alan Stern wrote: >>> Since in dummy_hcd all of this is much simpler I think that the device speed >>> should be determined by driver->speed and "which type of cable the >>> connection was made over - SS or HS". The "cable type" is exactly what the >>> module parameter is. >> >> I really don't understand this. You're going to have a module parameter >> for what type of cable is plugged in? > > It would be more accurate to say the module parameter will be used to > force the connection to run at a lower speed than the maximum possible. > This is kind of like what happens when you plug in a SuperSpeed device > using a USB-2 cable -- the connection runs at a lower speed than it > could have. if it's something like that, for sure we can have the module parameter. But plugging a USB2 gadget/function to a USB3-capable UDC/HCD should work fine. With Tatyana's patches, if we load a USB2 g_zero to dummy_hcd, enumeration will fail where it shouldn't. This has been my whole point ;-) Maybe I wasn't clear enough. >> What about the case where SuperSpeed enumeration >> fails and you have to fall back to high speed? > > If SuperSpeed enumeration fails, say because the device doesn't have > any SuperSpeed descriptors, xhci-hcd doesn't fall back to high speed, > does it? dummy-hcd should behave the same way. it should at least. Isn't that what happens between EHCI/OHCI ? HS Chirp sequencing fails, then we fall back to FullSpeed. >> It seems like you really >> need to handle both speeds and the speed fall back parameter in the same >> driver. Isn't there some other gadget driver that has a fall back to >> full or low speed when high speed enumeration fails? > > That's a property of the gadget driver, not the UDC driver. dummy-hcd > is a UDC driver (and an HCD too). USB3.0 dummy_hcd should still enumerate USB2.0 gadget drivers. -- balbi -- 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/