From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-3.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 780CFC54FCB for ; Sun, 26 Apr 2020 14:32:03 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 5F1682070A for ; Sun, 26 Apr 2020 14:32:03 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726202AbgDZOcA (ORCPT ); Sun, 26 Apr 2020 10:32:00 -0400 Received: from netrider.rowland.org ([192.131.102.5]:49747 "HELO netrider.rowland.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1725876AbgDZOb7 (ORCPT ); Sun, 26 Apr 2020 10:31:59 -0400 Received: (qmail 16225 invoked by uid 500); 26 Apr 2020 10:31:58 -0400 Received: from localhost (sendmail-bs@127.0.0.1) by localhost with SMTP; 26 Apr 2020 10:31:58 -0400 Date: Sun, 26 Apr 2020 10:31:58 -0400 (EDT) From: Alan Stern X-X-Sender: stern@netrider.rowland.org To: Vladimir Stankovic cc: gregkh@linuxfoundation.org, , , Subject: Re: [PATCH v5 5/8] usb: mausb_host: Introduce PAL processing In-Reply-To: <48e45671-1f07-c994-8083-04199822c818@displaylink.com> Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, 26 Apr 2020, Vladimir Stankovic wrote: > On 26.4.20. 02:32, Alan Stern wrote: > > On Sat, 25 Apr 2020 vladimir.stankovic@displaylink.com wrote: > > > >> Protocol adaptation layer (PAL) implementation has been added to > >> introduce MA-USB structures and logic. > >> > >> Signed-off-by: Vladimir Stankovic > > > > ... > > > >> + /* > >> + * Masking URB_SHORT_NOT_OK flag as SCSI driver is adding it where it > >> + * should not, so it is breaking the USB drive on the linux > >> + */ > >> + urb->transfer_flags &= ~URB_SHORT_NOT_OK; > > > > Removing the SHORT_NOT_OK flag is _not_ a valid thing to do. It will > > cause drivers to malfunction. > > > > Can you please explain this comment? > > > > What SCSI driver? > > > > When is the flag being added? > > > > How does it break USB drives? > > > > Why haven't you already reported this problem to the > > appropriate maintainers? > > > > Alan Stern > > > > Hi, > > Issue that removal of SHORT_NOT_OK flag addressed is linked to particular > set of Kingston USB 3.0 flash drives (super speed) - other USB flash drives > haven't had this flag set. Without this "fix", those Kingston flash drives > are not being enumerated properly. Please explain in detail how the enumeration of these Kingston flash drives fails. Or if such an explanation has already been posted, please provide a link to it. > This particular line was added in the early stage of development, during > enumeration process implementation. The reason why it remained in the code > since is because we haven't noticed any side-effects, even with various > USB devices being attached to remote MA-USB device, including flash drives, > cameras, wireless mice, etc. Come to think of it, the SHORT_NOT_OK flag is mainly used with HCDs that don't have scatter-gather support. Since your mausb driver does support scatter-gather, you most likely won't encounter any problems unless you go looking for them specifically. > The problem has been reported, and is actively being investigated. Where was the problem reported (URL to a mailing list archive)? Who is investigating it? > As soon as it gets addressed properly (w/o global negation of the flag), > a new patch will be pushed. Thank you. Alan Stern