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=-5.5 required=3.0 tests=BAYES_00,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 4EFF4C4167B for ; Fri, 4 Dec 2020 06:59:55 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 0490922597 for ; Fri, 4 Dec 2020 06:59:54 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727952AbgLDG7j (ORCPT ); Fri, 4 Dec 2020 01:59:39 -0500 Received: from mail-ej1-f66.google.com ([209.85.218.66]:42086 "EHLO mail-ej1-f66.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725601AbgLDG7i (ORCPT ); Fri, 4 Dec 2020 01:59:38 -0500 Received: by mail-ej1-f66.google.com with SMTP id d17so7134660ejy.9; Thu, 03 Dec 2020 22:59:22 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:cc:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=e50yAptPk4qvH2DjIDkzdRdD/+Aa+SiLK2zM+mJlFWA=; b=eC5k0J95DjW8FrZJhU3Z+5kXbR/eCy0IEYRe2JqcboV8SotoZ/2TOKp59zWAExaaEH 5Dbu3Ixe5HIHnQMFqE0cnQ9PciUFqkEFNA4MtWmt1GGL+BM0HKb/RksQgMxwlNYWS/iZ i1COKAnuGUocvAxCtZMAJVAcjJ6iJFhRi2aWinh2AiuVEFHWe+1/QwRC5wqeuybKwrWz vmlIf0He6BYEsJP4A4USmwrHbHyCPKZVin5CdRR4xQyA4IFi6vBPFQFoHc6qzUYiWIG7 jhZHdxLLk7ChHA8tdaG2EQ4KLQkJXu7T0Dy9QlangXMBHIhO7URP4qiq2XboSpZNSro2 qg/A== X-Gm-Message-State: AOAM533KuKBKMrUsVWgbHO0O6Snm1tu6drmTREAh2n4LrQ5zPeymmppf LD/KLUfAFTIXxgtNiZvaSTaisfZ6h7UNgQ== X-Google-Smtp-Source: ABdhPJy5MEfKbVUJFTnh1vKqmxmxnnoKlgi6kcqIAd4ISej8g/3EJ6ptUx8ssAV5yi5x1hhhmvLh+Q== X-Received: by 2002:a17:906:d72:: with SMTP id s18mr5900964ejh.110.1607065136221; Thu, 03 Dec 2020 22:58:56 -0800 (PST) Received: from ?IPv6:2a0b:e7c0:0:107::49? ([2a0b:e7c0:0:107::49]) by smtp.gmail.com with ESMTPSA id x20sm2418231ejv.66.2020.12.03.22.58.54 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 03 Dec 2020 22:58:55 -0800 (PST) Subject: Re: [PATCH 0/5] tty: add flag to suppress ready signalling on open To: Johan Hovold Cc: Mychaela Falconia , Greg Kroah-Hartman , "Mychaela N . Falconia" , linux-serial@vger.kernel.org, linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org References: <20201130153742.9163-1-johan@kernel.org> From: Jiri Slaby Message-ID: Date: Fri, 4 Dec 2020 07:58:53 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.5.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=iso-8859-2; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-usb@vger.kernel.org On 02. 12. 20, 12:48, Johan Hovold wrote: >>> but I question the >>> usefulness of doing so, as it is 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. If Johan or someone else can see a potential use >>> case for manipulating this new flag via termios (as opposed to sysfs >>> or USB-ID-based driver quirks), perhaps you could elaborate on it? >> >> We would need to (ab)use another open flag (e.g. O_DIRECT). I am not >> biased to either of solutions. > > Forgot to mention that using open-flags would prevent using standard > utilities like cat, echo and terminal programs. So for that reason a > termios and/or sysfs interface is also preferred. Nope, I meant it differently. You set it up once using the special open flag. Like with setserial, one sets I/O port, irqs etc. and then uses standard tools as the port is already set up (marked as NORDY in this case). thanks, -- js