From patchwork Thu Apr 30 16:14:35 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Alper Nebi Yasak X-Patchwork-Id: 214045 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=-9.6 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH, MAILING_LIST_MULTI, SIGNED_OFF_BY, SPF_HELO_NONE, SPF_PASS, USER_AGENT_GIT autolearn=ham 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 C5AC9C47247 for ; Thu, 30 Apr 2020 16:16:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9F83320873 for ; Thu, 30 Apr 2020 16:16:34 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="sosUSrAu" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727113AbgD3QQe (ORCPT ); Thu, 30 Apr 2020 12:16:34 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49346 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S1726405AbgD3QQd (ORCPT ); Thu, 30 Apr 2020 12:16:33 -0400 Received: from mail-lj1-x242.google.com (mail-lj1-x242.google.com [IPv6:2a00:1450:4864:20::242]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id DF708C035494; Thu, 30 Apr 2020 09:16:32 -0700 (PDT) Received: by mail-lj1-x242.google.com with SMTP id f18so7082335lja.13; Thu, 30 Apr 2020 09:16:32 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=dcawBkXikPYOd9gFykEVGPuWXUWfQrJeZCwUFjbXlT4=; b=sosUSrAuUHwXK5OEpDrkqaJHrO0GGy0Ln5+fNdN+gN6s5xxybYMfk62DTRz82hFfDW 3WsUtL5mZtTtjasdrGDXuLX2ENo0nhL8CRdGd74HWHwz3Y/lLcmgVn8w01cgM9gIYSWy 1ClW/qZfGqJQKSpQZiLtz7DccWTt1sbgjnej1CuSydRY/DBLa+BQdaaVd4SgxYuTZAc+ 2YgxHtxvdynliAeIBWW300Rq2M7JTEnyXdt/G4CdzegQM8ORS3/eBubBGzy2nENr9s66 tMOSZY6mY7hx0HwZufKzxtYA8dCj2iV167701I6iC3ADwXddcvMiFgS2X52N8DC6+Luj 21rA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=dcawBkXikPYOd9gFykEVGPuWXUWfQrJeZCwUFjbXlT4=; b=o08cn9zMoA4uM9+4lnDDW67hx5RyLW8+Tj8kRk0OuF2UnscoSKB3bLPXUKuviS3bpZ maQYdMqt9s9Et2HVBR4ZhaPsgHVXkdeBsVwOGE5Aa6eL5D19jNQZWGW8CB1W4jVQwNFz P0fzNYBs2EXMEyPdadM1mC0A2phOC1NqCZnCPDwobtGM45HLFYzn3Obfn6vLSxpZLZWj bGaxgXs3QOS68uKdNgLgvjQnMoyPtuqZEzhgD9u22Qc8H001P7+cYW+eIhyX9QDMoKuq Ihuafqjbqw9kKj+abPdH++fOwbPf3SBHLluVhotDI05NIVCB4r33IxbF6Xyrx2INMJzj Alaw== X-Gm-Message-State: AGi0Puam89ACaSus3+r+ICNVx3h2XvxBGgecdDzotc5mwrnw2hA3O6Ls 3owdKH/bFjDC0aCc9nfYKPI= X-Google-Smtp-Source: APiQypJlHPjg7i2J2gTNDSPTCeeNvzQBhsBhfepNh86Pej0Lou55gA4cVl+9dZI3HWGt3Ys5ggHMhQ== X-Received: by 2002:a2e:b012:: with SMTP id y18mr44709ljk.238.1588263391301; Thu, 30 Apr 2020 09:16:31 -0700 (PDT) Received: from localhost.localdomain ([178.233.178.9]) by smtp.gmail.com with ESMTPSA id k6sm60638lfm.91.2020.04.30.09.16.28 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 30 Apr 2020 09:16:30 -0700 (PDT) From: Alper Nebi Yasak To: Greg Kroah-Hartman , Jiri Slaby , Petr Mladek , Sergey Senozhatsky Cc: linux-serial@vger.kernel.org, Steven Rostedt , Alper Nebi Yasak , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Andrew Morton , Andy Shevchenko , Arvind Sankar , Benjamin Herrenschmidt , "David S. Miller" , Feng Tang Subject: [RFC PATCH v2 1/3] printk: Add function to set console to preferred console's driver Date: Thu, 30 Apr 2020 19:14:35 +0300 Message-Id: <20200430161438.17640-2-alpernebiyasak@gmail.com> X-Mailer: git-send-email 2.26.2 In-Reply-To: <20200430161438.17640-1-alpernebiyasak@gmail.com> References: <20200430161438.17640-1-alpernebiyasak@gmail.com> MIME-Version: 1.0 Sender: linux-serial-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-serial@vger.kernel.org Currently, add_preferred_console sets a preferred console, but doesn't actually change /dev/console to match it. That part is handled within register_device, where a newly registered console driver will be set as /dev/console if it matches the preferred console. However, if the relevant driver is already registered, the only way to set it as /dev/console is by un-registering and re-registering it. An example is the xenfb_make_preferred_console() function: console_lock(); for_each_console(c) { if (!strcmp(c->name, "tty") && c->index == 0) break; } console_unlock(); if (c) { unregister_console(c); c->flags |= CON_CONSDEV; c->flags &= ~CON_PRINTBUFFER; /* don't print again */ register_console(c); } The code above was introduced in commit 9e124fe16ff2 ("xen: Enable console tty by default in domU if it's not a dummy"). In short, it's aim is to set VT as the preferred console only after a working framebuffer is registered and thus VT is not the dummy device. This patch introduces an update_console_to_preferred function that handles the necessary /dev/console change. With this change, the example above can be replaced with: console_lock(); add_preferred_console("tty", 0, NULL); update_console_to_preferred(); console_unlock(); More importantly, these two calls can be moved to vt.c in order to bump its priority when a non-dummy backend for it is introduced, solving that problem in general. Signed-off-by: Alper Nebi Yasak --- Changes in v2: - Use the correct format when referencing a commit include/linux/console.h | 1 + kernel/printk/printk.c | 56 +++++++++++++++++++++++++++++++++++++++++ 2 files changed, 57 insertions(+) diff --git a/include/linux/console.h b/include/linux/console.h index 75dd20650fbe..4b3fa34be245 100644 --- a/include/linux/console.h +++ b/include/linux/console.h @@ -172,6 +172,7 @@ enum con_flush_mode { }; extern int add_preferred_console(char *name, int idx, char *options); +extern int update_console_to_preferred(void); extern void register_console(struct console *); extern int unregister_console(struct console *); extern struct console *console_drivers; diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c index 6ede4a7222e6..efda422203e4 100644 --- a/kernel/printk/printk.c +++ b/kernel/printk/printk.c @@ -2240,12 +2240,68 @@ __setup("console=", console_setup); * be used by arch-specific code either to override the user or more * commonly to provide a default console (ie from PROM variables) when * the user has not supplied one. + * + * Preferences set by this function don't take effect until the next + * time a matching driver for the preferred console is registered. If a + * matching driver was already registered, @update_console_to_preferred + * function can be used to set that as the preferred console driver. */ int add_preferred_console(char *name, int idx, char *options) { return __add_preferred_console(name, idx, options, NULL, false); } +/** + * update_console_to_preferred - set console to the preferred console's driver. + * + * Updates console_drivers and CON_CONSDEV flags so that an already + * registered and enabled console driver matching the preferred console + * is used as /dev/console. + * + * Must be called within console_lock();. + */ +int update_console_to_preferred(void) +{ + struct console_cmdline *c = NULL; + struct console *con = NULL; + struct console *tmp = NULL; + + if (preferred_console >= 0) + c = &console_cmdline[preferred_console]; + + if (!c || !c->name[0]) + return 0; + + for_each_console(con) { + if (!con->next || !(con->next->flags & CON_ENABLED)) + continue; + if (strcmp(c->name, con->next->name) != 0) + continue; + if (con->next->index >= 0 && + con->next->index != c->index) + continue; + break; + } + + if (!con) + return -ENODEV; + + pr_info("switching to console [%s%d]\n", + con->next->name, con->next->index); + + tmp = con->next; + con->next = con->next->next; + tmp->next = console_drivers; + console_drivers = tmp; + + if (console_drivers->next) + console_drivers->next->flags &= ~CON_CONSDEV; + console_drivers->flags |= CON_CONSDEV; + has_preferred_console = true; + + return 0; +} + bool console_suspend_enabled = true; EXPORT_SYMBOL(console_suspend_enabled);