Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756165AbaAJPMn (ORCPT ); Fri, 10 Jan 2014 10:12:43 -0500 Received: from iolanthe.rowland.org ([192.131.102.54]:47504 "HELO iolanthe.rowland.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1753223AbaAJPMi (ORCPT ); Fri, 10 Jan 2014 10:12:38 -0500 Date: Fri, 10 Jan 2014 10:12:37 -0500 (EST) From: Alan Stern X-X-Sender: stern@iolanthe.rowland.org To: Sarah Sharp cc: walt , David Laight , Greg Kroah-Hartman , Linux Kernel , "stable@vger.kernel.org" , "linux-usb@vger.kernel.org" , "linux-scsi@vger.kernel.org" Subject: Re: [PATCH 3.12 033/118] usb: xhci: Link TRB must not occur within a USB payload burst In-Reply-To: <20140109235045.GA17660@xanatos> 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 On Thu, 9 Jan 2014, Sarah Sharp wrote: > > I can't see anything obvious either. > > However there is no response to the 'stop endpoint' command. > > Section 4.6.9 (page 107 of rev1.0) states that the controller will complete > > any USB IN or OUT transaction before raising the command completion event. > > Possibly it is too 'stuck' to complete the transaction? > > The host has to stop processing the transaction, it can't "wait" for the > transaction to finish. "The Stop Endpoint Command is expected to stop > endpoint activity as soon as possible, which may mean that it stops in > the middle of a TRB." Just to clarify for Walt: There's a difference between a transaction and a transfer. Transfers can take an indefinitely long time to complete, because the device doesn't have to accept or send any data until it is ready. By contrast, transactions have sharply bounded lifetimes. A transaction consists of some maximum number of packets (usually 3, sometimes a little more) with upper limits on the time intervals between them. A TRB lies somewhere between a transfer and a transaction. A single TRB can encompass a single transaction or multiple transactions, and a single transfer can involve more than one TRB. 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/