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 1B311C33CA4 for ; Fri, 10 Jan 2020 22:10:37 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id E269E20678 for ; Fri, 10 Jan 2020 22:10:36 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=arista.com header.i=@arista.com header.b="NOpOBQRE" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727370AbgAJWKg (ORCPT ); Fri, 10 Jan 2020 17:10:36 -0500 Received: from mail-pg1-f196.google.com ([209.85.215.196]:42493 "EHLO mail-pg1-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727189AbgAJWKf (ORCPT ); Fri, 10 Jan 2020 17:10:35 -0500 Received: by mail-pg1-f196.google.com with SMTP id s64so1611361pgb.9 for ; Fri, 10 Jan 2020 14:10:35 -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=FflZTkcc1ts8SyPh1Tv6O3mO6woDMPvlWHZ4MJqJNrs=; b=NOpOBQRE66u6KQN87/vkmAkItKOSF4ij4xbS9VnxPrl+sbpTcbCd6GfbYid59Uimc9 ARE5i9QvhqmIGUARO+5nRQQ3fMm1FExit60q2VXJKjSkTlSCDuVpxR8Kz68/5leDKeG+ lsIyS6w0ShaK/JeNAXkGbemqcBQYtv73CmfldBMfiGT4W+f0qBuMR3SGl1xczxNbGvs9 WVe0swkgvPGojIyB/1YfgZfGPx2z5aIpZICIyCTl1DTU2SSpEVyir+OfPhSJ7WncC5qV ujd8osY5v3oblUdBcBZ2N/2wyEu4ysqlXpgxe4xKvogWmjNUF9q1c6yFzzTE+FL2Fej6 ZinA== 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=FflZTkcc1ts8SyPh1Tv6O3mO6woDMPvlWHZ4MJqJNrs=; b=i8Ylg1sgKA+OZNA3f0lPH3FhlKpbPlGnlqoGry0mgpKfk+6WK0oaVo58rQhQayyKLm YAxdjD3iRca1fgDjhlBFpxKnnTiMSVQoE74XP6gIXsvYqoJOfpvbElCqk7WCs68V9ThG 1P+lFIuFDPGBB9v5ZJhz131Tf6SCRS5qX85X6c0/HSL2eKV11MmTfFUkGbJXwKa+ZhYI qv3gGrHya0UbZJou6bsAXmo8fZam4Lg+r+wYjX0R3tq4510F9sAN/MLdz0FrgCAx3hUv tDVQXmD8Dota/ezPgtQo+TmpXCaBCDFJzLcpBfPMEgB/ASzzP71zGImQgrBnSSYE/Jmf I52w== X-Gm-Message-State: APjAAAWssTI7mS2H25G3kwoaWmPuKQCvUM5yBoTx4IixhgbtWpQkFwyQ cfFmjMIj+tYbVdBcdJSLlOP0eQ== X-Google-Smtp-Source: APXvYqwPVEhjrJvHFlfWZvKdXjGSTwzhF4/7AP0pRc7ulrfBKq+w05WIwBr+6YtpkcxiucBcZA+ZbQ== X-Received: by 2002:a63:7045:: with SMTP id a5mr7179821pgn.49.1578694234777; Fri, 10 Jan 2020 14:10:34 -0800 (PST) Received: from [10.83.36.153] ([217.173.96.166]) by smtp.gmail.com with ESMTPSA id g24sm4238709pfk.92.2020.01.10.14.10.27 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 10 Jan 2020 14:10:33 -0800 (PST) Subject: Re: [PATCH-next 3/3] serial/sysrq: Add MAGIC_SYSRQ_SERIAL_SEQUENCE To: Joe Perches , linux-kernel@vger.kernel.org Cc: Dmitry Safonov <0x7f454c46@gmail.com>, Greg Kroah-Hartman , Jiri Slaby , Vasiliy Khoruzhick , linux-serial@vger.kernel.org References: <20200109215444.95995-1-dima@arista.com> <20200109215444.95995-4-dima@arista.com> <5293a7cb1ccb16275ddb36c7f26fb9e83f4fac9b.camel@perches.com> From: Dmitry Safonov Message-ID: <056bff50-f67e-f00f-c98f-ccb427344691@arista.com> Date: Fri, 10 Jan 2020 22:10:15 +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: <5293a7cb1ccb16275ddb36c7f26fb9e83f4fac9b.camel@perches.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Joe, On 1/10/20 4:50 PM, Joe Perches wrote: > On Thu, 2020-01-09 at 21:54 +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. > > trivia: > >> diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c > [] >> @@ -3081,6 +3081,38 @@ void uart_insert_char(struct uart_port *port, unsigned int status, > [] >> +const char sysrq_toggle_seq[] = CONFIG_MAGIC_SYSRQ_SERIAL_SEQUENCE; > > static const? Will do, thanks! > >> +static int uart_try_toggle_sysrq(struct uart_port *port, unsigned int ch) > > This function return might read better as bool not int Yeah, no hard feelings, will convert. [..] >> @@ -243,10 +243,10 @@ struct uart_port { >> unsigned long sysrq; /* sysrq timeout */ >> unsigned int sysrq_ch; /* char for sysrq */ >> unsigned char has_sysrq; >> + unsigned char sysrq_seq; /* index in sysrq_toggle_seq */ > > unsigned int? > > Or maybe set a maximum length of MAGIC_SYSRQ_SERIAL_SEQUENCE. I think, 256 chars should be enough to send on serial (c) I'm not aware of a way to put the max string length in Kconfig, so I did in the patch: BUILD_BUG_ON(ARRAY_SIZE(sysrq_toggle_seq) >= sizeof(port->sysrq_seq)*U8_MAX); Do you have something more elegant in your mind? Thanks, Dmitry