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=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_2 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 BB5F1C433E0 for ; Wed, 27 May 2020 10:41:16 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9CE5820888 for ; Wed, 27 May 2020 10:41:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729937AbgE0KlQ (ORCPT ); Wed, 27 May 2020 06:41:16 -0400 Received: from mx2.suse.de ([195.135.220.15]:51834 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729828AbgE0KlO (ORCPT ); Wed, 27 May 2020 06:41:14 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx2.suse.de (Postfix) with ESMTP id 80568AEEF; Wed, 27 May 2020 10:41:16 +0000 (UTC) Message-ID: <1590576068.2838.56.camel@suse.com> Subject: Re: ttyACM: disabled by hub (EMI?), re-enabling... Causes garbage chars & disconnect From: Oliver Neukum To: Joakim Tjernlund , "linux-usb@vger.kernel.org" Date: Wed, 27 May 2020 12:41:08 +0200 In-Reply-To: References: <6a4fe396ab5ae6cda548e904c57bc823103999d7.camel@infinera.com> <1590418977.2838.16.camel@suse.com> <1590482853.2838.26.camel@suse.com> <8cf71160e703a18b28d27a844406d42f6cadf39b.camel@infinera.com> <1590488084.2838.34.camel@suse.com> <42c92312c74e90e5507de4103bd15bbbe175f98d.camel@infinera.com> <4c2bd25aa7f6672cb132487f7af6a787ffc1fab6.camel@infinera.com> <1590568683.2838.42.camel@suse.com> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.26.6 Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-usb-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-usb@vger.kernel.org Am Mittwoch, den 27.05.2020, 09:40 +0000 schrieb Joakim Tjernlund: > On Wed, 2020-05-27 at 10:38 +0200, Oliver Neukum wrote: > > CAUTION: This email originated from outside of the organization. Do not click links or open attachments unless you recognize the sender and know the content is safe. > > > > > > Am Dienstag, den 26.05.2020, 17:19 +0000 schrieb Joakim Tjernlund: > > > > > > This "u-boot SPL" is the first thing u-boot writes and somehow this is remembered, I assume, by cdc_acm > > > and gets echoed back when I open ttyACM0 > > > > Hi, > > > > that makes sense, but it is not something that we could really > > change in CDC-ACM, I am afraid. > > Why not? CDC-ACM should echo back anything it has received before open of ttyACM Well, there is an inherent race condition with loading the module I am afraid. By default cdc-acm should actually echo. You can set the DISABLE_ECHO echo quirk for your device if you want to get rid of it. Is CDC-ACM violating some standard with respect to echoing? Changing defaults really hurts users, no matter what you do. Regards Oliver