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=-5.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_1 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 795FEC433E6 for ; Tue, 23 Feb 2021 15:59:18 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2D1BB64EC9 for ; Tue, 23 Feb 2021 15:59:18 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233337AbhBWP7E convert rfc822-to-8bit (ORCPT ); Tue, 23 Feb 2021 10:59:04 -0500 Received: from bee.birch.relay.mailchannels.net ([23.83.209.14]:2558 "EHLO bee.birch.relay.mailchannels.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233313AbhBWP64 (ORCPT ); Tue, 23 Feb 2021 10:58:56 -0500 X-Sender-Id: dreamhost|x-authsender|smtp@contentfirst.com Received: from relay.mailchannels.net (localhost [127.0.0.1]) by relay.mailchannels.net (Postfix) with ESMTP id 52BB932377F; Tue, 23 Feb 2021 15:57:13 +0000 (UTC) Received: from pdx1-sub0-mail-a45.g.dreamhost.com (100-96-16-18.trex.outbound.svc.cluster.local [100.96.16.18]) (Authenticated sender: dreamhost) by relay.mailchannels.net (Postfix) with ESMTPA id CACEA32367E; Tue, 23 Feb 2021 15:57:12 +0000 (UTC) X-Sender-Id: dreamhost|x-authsender|smtp@contentfirst.com Received: from pdx1-sub0-mail-a45.g.dreamhost.com (pop.dreamhost.com [64.90.62.162]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384) by 100.96.16.18 (trex/6.0.2); Tue, 23 Feb 2021 15:57:13 +0000 X-MC-Relay: Neutral X-MailChannels-SenderId: dreamhost|x-authsender|smtp@contentfirst.com X-MailChannels-Auth-Id: dreamhost X-Snatch-Abortive: 79a5151838c66d0c_1614095833137_1377275420 X-MC-Loop-Signature: 1614095833137:1106550808 X-MC-Ingress-Time: 1614095833137 Received: from pdx1-sub0-mail-a45.g.dreamhost.com (localhost [127.0.0.1]) by pdx1-sub0-mail-a45.g.dreamhost.com (Postfix) with ESMTP id 9600D7F03C; Tue, 23 Feb 2021 07:57:12 -0800 (PST) Received: from industrynumbers.com (pool-100-15-209-187.washdc.fios.verizon.net [100.15.209.187]) (using TLSv1.2 with cipher ADH-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) (Authenticated sender: smtp@contentfirst.com) by pdx1-sub0-mail-a45.g.dreamhost.com (Postfix) with ESMTPSA id 754A47F11C; Tue, 23 Feb 2021 07:57:10 -0800 (PST) Received: from industrynumbers.com (localhost [127.0.0.1]) by industrynumbers.com (Postfix) with ESMTP id 23DDA282D7A; Tue, 23 Feb 2021 10:57:09 -0500 (EST) To: Johan Hovold Cc: charles-yeh@prolific.com.tw, linux-serial@vger.kernel.org, linux-usb@vger.kernel.org, Charles Yeh , Joe Abbott References: <3aee5708-7961-f464-8c5f-6685d96920d6@IEEE.org> <0f9caf26-af58-13a9-9947-47bb646f505e@IEEE.org> <780b9aa6-890d-47fd-d6b2-cd9a39f7634a@IEEE.org> X-DH-BACKEND: pdx1-sub0-mail-a45 From: "Michael G. Katzmann" Subject: Re: non-standard baud rates with Prolific 2303 USB-serial Message-ID: Date: Tue, 23 Feb 2021 10:57:09 -0500 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.7.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8BIT Content-Language: en-US Precedence: bulk List-ID: X-Mailing-List: linux-usb@vger.kernel.org On 2/23/21 10:43 AM, Johan Hovold wrote: > On Tue, Feb 23, 2021 at 09:58:47AM -0500, Michael G. Katzmann wrote: >> Is it that we are presuming that what Prolific is telling us is true >> and only Joe and I are actually measuring the data rate?  (i.e. why >> does the Prolific Windows driver set the values as Joe found ???) > I'm starting to think they've added some alternate baud rate encoding in > order to make life harder for the people pushing (or unknowingly buying) > counterfeit devices. > > As you say, why else would the Windows driver support this encoding? I find that  'Halon;'s razor' is helpful in these situations...  I can't think that messing with people who use old teleprinters would be useful in protecting one's products 8-) If Joe has some wireshark traces we can see if there are any vendor specific USB packets. If not I can try it (I'd be starting from scratch as I've only use wireshark on Linux). I presume you can't see any differentiators in the normal USB identifiers that we can use.  If someone has a device that works under the existing driver, it would be helpful to see if the modified scheme also works on those devices?