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=-5.4 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=unavailable 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 DFB91C33CB6 for ; Tue, 14 Jan 2020 17:37:12 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id BB43224679 for ; Tue, 14 Jan 2020 17:37:12 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=arista.com header.i=@arista.com header.b="foRWn/Sx" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728882AbgANRhF (ORCPT ); Tue, 14 Jan 2020 12:37:05 -0500 Received: from mail-pg1-f193.google.com ([209.85.215.193]:41109 "EHLO mail-pg1-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728880AbgANRhE (ORCPT ); Tue, 14 Jan 2020 12:37:04 -0500 Received: by mail-pg1-f193.google.com with SMTP id x8so6705582pgk.8 for ; Tue, 14 Jan 2020 09:37:04 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=arista.com; s=googlenew; h=subject:to:cc:references:from:message-id:date:user-agent :mime-version:in-reply-to:content-language:content-transfer-encoding; bh=EC1V31kkUKO1e4THTwUpln5DsH8XNb9uCr/r/2oHaQg=; b=foRWn/SxPpwzIYpPv9YpeG9HklGuam9AgV1o5mwQsvaYNVZJ8JxscJsD7TgVtkbQob oRlJfldyaUDAJdT3dKT75Hb9FuALBQMR4mgZUCpHxptwaK6YPnezeRhYMO0JlZCOA+X9 TgbTcUIKzmtIO7/aLb5aPmJ4MMyoGS3nicS8HxyAQAJDNEh03y4LWuuG5mzqFblUr5Oo vxCvNyYHDUu4/33/3Nb+XPCa62GAN7cG1NsYjuH0WsWPpBWpsLOY7n6iwdsaXy1EIhCI KE+O9mWenc4TyeytPTsn2vW4RTofbvX0t6XJIkqfvyAyMfqYtZKgUaD3AAONtpynBVYR a8Vg== 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=EC1V31kkUKO1e4THTwUpln5DsH8XNb9uCr/r/2oHaQg=; b=ZCdjtPJOpOEE00lBrba1aoQipiQNHX9pRweP3P1EPqxYcivKOVT0dMgDWVgmh+QHOr z0ki0IQZHRlAfnKEdt5aITeU6Z6WywMbAxePAVYAWqglk2Lm3dtMpkGBpdsi7SJYKZPa VG/lg7tKHxsAhkuM5Fs+EtckricLh/rYLdPbLXu9ApssI5KJoG5N/0IBXobf5iJ27zSG vguigwcOLa7BGLtSMhrVsb1d3g57H/jrWvjtoNhNl5IFWzRKpV6H4qyqtOkGdNfyTd0V CKycS/H7jO6rX3m6Sd7+7J812ApHG6Pca6aZKLL9h74ZFSskseKUPk+FVDX2VedpwNsf AfjA== X-Gm-Message-State: APjAAAWgm82FruFMAU7fITS8yHAMF/qpPvr2iCPJqyu/e/FvNyesu2Lo Ep7ioGPkcVcTk/TzpsehjOdKhg== X-Google-Smtp-Source: APXvYqyzpnXWDZlOjta8/q0rFUjicssGmDGoJZEC4U64CAy+P3MaBYClXvzSbj7vwaK72Y0QxRVj4Q== X-Received: by 2002:a62:b508:: with SMTP id y8mr26409909pfe.251.1579023423632; Tue, 14 Jan 2020 09:37:03 -0800 (PST) Received: from [10.83.36.153] ([217.173.96.166]) by smtp.gmail.com with ESMTPSA id z11sm19621730pfk.96.2020.01.14.09.37.00 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 14 Jan 2020 09:37:02 -0800 (PST) Subject: Re: [PATCHv2-next 2/3] serial/sysrq: Add MAGIC_SYSRQ_SERIAL_SEQUENCE To: Joe Perches , linux-kernel@vger.kernel.org Cc: Dmitry Safonov <0x7f454c46@gmail.com>, Greg Kroah-Hartman , Iurii Zaikin , Jiri Slaby , Randy Dunlap , Vasiliy Khoruzhick , linux-serial@vger.kernel.org References: <20200114171912.261787-1-dima@arista.com> <20200114171912.261787-3-dima@arista.com> <24455cb643415cf9379bb8343525b844ead4236b.camel@perches.com> From: Dmitry Safonov Message-ID: Date: Tue, 14 Jan 2020 17:36:59 +0000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.3.0 MIME-Version: 1.0 In-Reply-To: <24455cb643415cf9379bb8343525b844ead4236b.camel@perches.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-serial-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-serial@vger.kernel.org Hi Joe, On 1/14/20 5:30 PM, Joe Perches wrote: > On Tue, 2020-01-14 at 17:19 +0000, Dmitry Safonov wrote: >> Many embedded boards have a disconnected TTL level serial which can >> generate some garbage that can lead to spurious false sysrq detects. > > Hi again Dmitry. trivia: > >> diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c > [] >> +/** >> + * uart_try_toggle_sysrq - Enables SysRq from serial line >> + * @port: uart_port structure where char(s) after BREAK met >> + * @ch: new character in the sequence after received BREAK >> + * >> + * Enables magic SysRq when the required sequence is met on port >> + * (see CONFIG_MAGIC_SYSRQ_SERIAL_SEQUENCE). >> + * >> + * Returns 0 if @ch is out of enabling sequence and should be >> + * handled some other way, 1 if @ch was consumed. >> + */ > > Normally bool functions return values are true/false not 1/0. I agree. Though, somehow it seems to me that `return 1` is a bit closer to "one character consumed" than "return true". Again, no hard feelings, just a preference. I can change those returns to bools if you insist :) > >> +static bool uart_try_toggle_sysrq(struct uart_port *port, unsigned int ch) >> +{ >> + if (ARRAY_SIZE(sysrq_toggle_seq) <= 1) >> + return 0; > > return false; > > etc... > > Thanks, Dmitry