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, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED 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 D5E14C433E3 for ; Sat, 1 Aug 2020 13:28:19 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id AD1C7208C7 for ; Sat, 1 Aug 2020 13:28:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726211AbgHAN2T (ORCPT ); Sat, 1 Aug 2020 09:28:19 -0400 Received: from relay3-d.mail.gandi.net ([217.70.183.195]:40143 "EHLO relay3-d.mail.gandi.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725306AbgHAN2S (ORCPT ); Sat, 1 Aug 2020 09:28:18 -0400 X-Originating-IP: 90.66.108.79 Received: from localhost (lfbn-lyo-1-1932-79.w90-66.abo.wanadoo.fr [90.66.108.79]) (Authenticated sender: alexandre.belloni@bootlin.com) by relay3-d.mail.gandi.net (Postfix) with ESMTPSA id BF87C60003; Sat, 1 Aug 2020 13:28:14 +0000 (UTC) Date: Sat, 1 Aug 2020 15:28:13 +0200 From: Alexandre Belloni To: Grant Feng Cc: a.zummo@towertech.it, linux-rtc@vger.kernel.org Subject: Re: [PATCH] rtc: interface:: 1969-12-31T23:59:59 is set as rtc_time if rtc_time is invalid in __rtc_read_time Message-ID: <20200801132813.GE3679@piout.net> References: <20200801112007.2148-1-von81@163.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20200801112007.2148-1-von81@163.com> Sender: linux-rtc-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-rtc@vger.kernel.org Hi, On 01/08/2020 19:20:07+0800, Grant Feng wrote: > 1969-12-31T23:59:59 is an error more clear than Invalid argument Definitively not, 1969-12-31T23:59:59 is a valid date and should not be returned when it is known the current date is not set in the RTC. > > For example, when the RTC clock is not set, it will print a kernel > error log every time someone tries to read the clock: > ~ # hwclock -r > hwclock: RTC_RD_TIME: Invalid argument > > It's clear and easy to understand what happened if print > 1969-12-31T23:59:59 in this situation： > ~ # hwclock -r > Wed Dec 31 23:59:59 1969 0.000000 seconds > How do you know this is an error an not what is actually set on the RTC? -- Alexandre Belloni, Bootlin Embedded Linux and Kernel engineering https://bootlin.com