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=-19.1 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=ham 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 6942AC433EF for ; Sat, 4 Sep 2021 16:17:39 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4E56860EFD for ; Sat, 4 Sep 2021 16:17:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236873AbhIDQSj (ORCPT ); Sat, 4 Sep 2021 12:18:39 -0400 Received: from informare.org ([217.11.52.70]:40646 "EHLO informare.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236830AbhIDQSj (ORCPT ); Sat, 4 Sep 2021 12:18:39 -0400 Received: (qmail 27516 invoked from network); 4 Sep 2021 16:17:36 -0000 Received: from unknown (HELO ?192.168.2.105?) (faber@faberman.de@87.133.154.214) by 0 with ESMTPA; 4 Sep 2021 16:17:36 -0000 Subject: Re: [PATCH] usb: gadget: f_mass_storage: Shut down mass storage device when USB connection is shut, down. To: Alan Stern Cc: gregkh@linuxfoundation.org, linux-usb@vger.kernel.org References: <5f9fbabd-2e2c-9389-446d-3bd1dd954a82@faberman.de> <20210904160951.GA493355@rowland.harvard.edu> From: Florian Faber Message-ID: Date: Sat, 4 Sep 2021 18:17:36 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.13.0 MIME-Version: 1.0 In-Reply-To: <20210904160951.GA493355@rowland.harvard.edu> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-usb@vger.kernel.org On 9/4/21 6:09 PM, Alan Stern wrote: > On Sat, Sep 04, 2021 at 05:32:58PM +0200, Florian Faber wrote: >> f_mass_storage continues to send out packets after the connection to the USB >> host has been terminated, ignoring the error status. > > The driver doesn't send packets after the connection has been terminated -- > that would be impossible. It may _try_ to send packets, but it can't > actually send anything unless the hosts asks for the data. There's nothing > wrong with trying and failing. Correct, that could have been expressed more clearly. > >> Signed-off-by: Florian Faber >> >> --- >> drivers/usb/gadget/function/f_mass_storage.c | 4 ++++ >> 1 file changed, 4 insertions(+) >> >> diff --git a/drivers/usb/gadget/function/f_mass_storage.c >> b/drivers/usb/gadget/function/f_mass_storage.c >> index 6ad669dde41c..1e73ba629e43 100644 >> --- a/drivers/usb/gadget/function/f_mass_storage.c >> +++ b/drivers/usb/gadget/function/f_mass_storage.c >> @@ -529,6 +529,10 @@ static int start_transfer(struct fsg_dev *fsg, struct >> usb_ep *ep, >> /* We can't do much more than wait for a reset */ >> req->status = rc; >> >> + if (rc==-ESHUTDOWN) { >> + fsg->common->running = 0; >> + } >> + > > This is wrong because it isn't what common->running means. common->running > means that the mass-storage configuration has been set by the host; it has > nothing to do with whether or not the USB cable is connected. So it is OK to keep the thread running and _trying_ to send out packets all the time until another USB host is plugged in, wasting resources? I would argue that the removal of a USB host is an implicit configuration change. Flo -- Machines can do the work, so people have time to think.