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=-4.0 required=3.0 tests=BAYES_00,MAILING_LIST_MULTI, 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 B0D88C64E7A for ; Tue, 1 Dec 2020 09:28:11 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 62A9F20674 for ; Tue, 1 Dec 2020 09:28:11 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2387428AbgLAJ2J (ORCPT ); Tue, 1 Dec 2020 04:28:09 -0500 Received: from mail-lj1-f196.google.com ([209.85.208.196]:40173 "EHLO mail-lj1-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2388486AbgLAJBK (ORCPT ); Tue, 1 Dec 2020 04:01:10 -0500 Received: by mail-lj1-f196.google.com with SMTP id y10so1629009ljc.7 for ; Tue, 01 Dec 2020 01:00:54 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=3FAzLAzbTqnDyPheEy8JH3X2tG5szlEVlz/oM+HlaVk=; b=sIaC1ULscSRQmu3UlkJAG54DvD+7nf9FeIIKGx8GEa2Oq3JiN1QUk+CtlTapB4TVsv Bq4y4FMXOY3yfy25yTtVt7YYxvzMtkw7AuY6WIYjnJ4cc3s81X32CnGp5SUEX6h2dLyu iYwPpTX+pIpMK9V4AQQGBNTzCQc1bs3V43sQOD7DX1Hjr0WWPlZ8v/D0VzG1lDlApaCK U7O84MyIOPVeJQz5sQObw+16+v1ijyv9RGERR4pxU7PMc+pl7a9DsG70mFzSMzn5gLf/ G6lWDXI7EDwj7VAOV3pn+M3mlQ6M8NLSKk+6TwJS9GowQaRKaC3o+04OP6ISiFiiTYWw kljA== X-Gm-Message-State: AOAM5322TQeTGZApkzZh5a1au0FG/myKHbJ4qmtbd5mILyq+wCqF4EHu G4ZX7WcaSzdlJPgAo6HfFP8= X-Google-Smtp-Source: ABdhPJzA31eo/gDXCV+MQixIrs2aGUatNx1gAw8nspCyE5ZQlSZTaJNaGuPaXR7ORt56OL/DBvH0ZA== X-Received: by 2002:a2e:9a98:: with SMTP id p24mr796270lji.418.1606813228669; Tue, 01 Dec 2020 01:00:28 -0800 (PST) Received: from xi.terra (c-beaee455.07-184-6d6c6d4.bbcust.telenor.se. [85.228.174.190]) by smtp.gmail.com with ESMTPSA id 14sm130683lfq.221.2020.12.01.01.00.27 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 01 Dec 2020 01:00:27 -0800 (PST) Received: from johan by xi.terra with local (Exim 4.93.0.4) (envelope-from ) id 1kk1Wq-0003LV-Sc; Tue, 01 Dec 2020 10:00:57 +0100 Date: Tue, 1 Dec 2020 10:00:56 +0100 From: Johan Hovold To: Mychaela Falconia Cc: Johan Hovold , linux-usb@vger.kernel.org Subject: Re: [PATCH 0/3] a family of FTDI-based devices that need ftdi_sio quirks Message-ID: References: <20200916015621.EFCDA374023F@freecalypso.org> <20200929101330.GQ24441@localhost> <20201005105722.GN5141@localhost> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-usb@vger.kernel.org On Mon, Nov 30, 2020 at 12:15:51PM -0800, Mychaela Falconia wrote: > > I'm adding a new tty port flag that can be used to suppress the > > assertion of DTR/RTS to signal DTE readiness on open named NORDY. > > Eventually we can expose it through termios to match HUPCL that controls > > the behaviour on final close. For now I'm only adding a sysfs interface > > but that also allows control over these signals on first open. > > I don't see how exposing this new flag via termios would be of any use > (it's a chicken and egg problem: one needs to open the tty device in > order to do termios ioctls on it, and if that initial open triggers > DTR/RTS hardware actions, then the end user is still screwed), but > making this flag accessible for setting and clearing via sysfs is a > good idea. Yeah, as I mentioned in the other thread a termios flag would not be sufficient for your use case, but there could be other applications that are more tolerant but still want control after first open. I believe this is also the way Win32, which you referred to earlier, works. Johan