From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail.zytor.com (terminus.zytor.com [198.137.202.136]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 6926133F388; Wed, 12 Nov 2025 16:10:03 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=198.137.202.136 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1762963805; cv=none; b=iyq02dXakIVvKJJtHjmtZegkvuX+Ki1j13u31GVnbUzH09h0ceU2YCNmWaNljOh4alT6cuYzatYxmtlTCZVQ+u3pp5K/xLIAfu8o0847rTbq4t6Y9xPyr+4zpX0ZOybg2cTenfFRPVwGBWzsrqQGhcinMU2CQPkrIjUHijzIEJ0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1762963805; c=relaxed/simple; bh=6+90iYt8yHn6fLVeRcRMn5yECTpBE605bYsebObkKiA=; h=Date:From:To:CC:Subject:In-Reply-To:References:Message-ID: MIME-Version:Content-Type; b=MmLevz4BdhQsNSb86nYL2h2099Mjk1208FFxj7cquL4QBKGniTpiZOuo4B6lzmo6NH1Js5hBHxCQjE84rCe1+LSjSiN227H4b1Grla6DHJx8Z2+5446WMAjp76I4/lTnwBN4ijXTsyxFzvW+BnfjMXmd6NsMrOS+vFITouBTfJI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=zytor.com; spf=pass smtp.mailfrom=zytor.com; dkim=fail (2048-bit key) header.d=zytor.com header.i=@zytor.com header.b=gs7yr+ih reason="signature verification failed"; arc=none smtp.client-ip=198.137.202.136 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=zytor.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=zytor.com Authentication-Results: smtp.subspace.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=zytor.com header.i=@zytor.com header.b="gs7yr+ih" Received: from ehlo.thunderbird.net ([172.59.162.180]) (authenticated bits=0) by mail.zytor.com (8.18.1/8.17.1) with ESMTPSA id 5ACG9qKk858789 (version=TLSv1.3 cipher=TLS_AES_128_GCM_SHA256 bits=128 verify=NO); Wed, 12 Nov 2025 08:09:53 -0800 DKIM-Filter: OpenDKIM Filter v2.11.0 mail.zytor.com 5ACG9qKk858789 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=zytor.com; s=2025102301; t=1762963794; bh=heGREnEy97DJ/3PBLnuPWHyDMClDirtaVhwc7KBGZD8=; h=Date:From:To:CC:Subject:In-Reply-To:References:From; b=gs7yr+ihaeLF4QpSBvoh3wuHOzShTiGaY57Urvlxkap6MmKJc1LlzHWO8CyOn61+w gVc4aoheKzEVojPfU+eJLDUTceZKBHKeQA5ZBTuBYuDySrmcBbwp/mTK17UsHdv++V Fc8e9dfkZOfVe39kPFZHq3+01Y/RkFXsU2OFZ7YvJl3/+Ua5mCGyhZn2uoSXiDplg/ AgRtj/73RtezqVMns+B4X6//QBzpPZOW7XDloRZquelz0jW8k8ZezvL2jDA8BW6VG5 VAvhXF7riHKl4rbJdyHP7LP8Zf7SqAid5Q97nOlBgM/ViIUvT6rQKpFfkDDy+E+U8a TaQxHrwbgkxQA== Date: Wed, 12 Nov 2025 08:09:45 -0800 From: "H. Peter Anvin" To: Greg KH CC: "Theodore Ts'o" , Maarten Brock , "linux-serial@vger.kernel.org" , "linux-api@vger.kernel.org" , LKML Subject: Re: RFC: Serial port DTR/RTS - O_NRESETDEV User-Agent: K-9 Mail for Android In-Reply-To: <2025111214-doily-anyway-b24b@gregkh> References: <20251107173743.GA3131573@mit.edu> <20251110033556.GC2988753@mit.edu> <20251110201933.GH2988753@mit.edu> <0F8021E8-F288-4669-8195-9948844E36FD@zytor.com> <20251111035143.GJ2988753@mit.edu> <2025111214-doily-anyway-b24b@gregkh> Message-ID: <6DBB5931-ACD4-4174-9FCE-96C45FFC4603@zytor.com> Precedence: bulk X-Mailing-List: linux-api@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable On November 12, 2025 3:22:56 AM PST, Greg KH = wrote: >On Mon, Nov 10, 2025 at 07:57:22PM -0800, H=2E Peter Anvin wrote: >> Honestly, though, I'm far less interested in what 8250-based hardware d= oes than e=2Eg=2E USB=2E > >hahahahahahaha {snort} > >Hah=2E that's a good one=2E > >Oh, you aren't kidding=2E > >Wow, good luck with this=2E USB-serial adaptors are all over the place, >some have real uarts in them (and so do buffering in the device, and >line handling in odd ways when powered up), and some are almost just a >straight pipe through to the USB host with control line handling ideas >tacked on to the side as an afterthought, if at all=2E > >There is no standard here, they all work differently, and even work >differently across the same device type with just barely enough hints >for us to determine what is going on=2E > >So don't worry about USB, if you throw that into the mix, all bets are >off and you should NEVER rely on that=2E > >Remeber USB->serial was explicitly rejected by the USB standard group, >only to have it come back in the "side door" through the spec process >when it turned out that Microsoft hated having to write a zillion >different vendor-specific drivers because the vendor provided ones kept >crashing user's machines=2E So what we ended up with was "just enough" t= o >make it through the spec process, and even then line signals are >probably never tested so you can't rely on them=2E > >good luck! > >greg "this brought up too many bad memories" k-h Ugh=2E I have made it very clear that I am very aware that there is broken hardwa= re=2E=20 What I'm trying to do is to deal with the (occasional) case of *non*-broke= n hardware=2E Right now Linux breaks the non-broken hardware for it, and I = don't think the existence of broken hardware is a good justification for th= at=2E