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=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED 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 D1650C3279B for ; Sun, 8 Jul 2018 10:49:48 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4E8EF2087F for ; Sun, 8 Jul 2018 10:49:48 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 4E8EF2087F Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=linux-m68k.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932842AbeGHKtn (ORCPT ); Sun, 8 Jul 2018 06:49:43 -0400 Received: from mail-ua0-f195.google.com ([209.85.217.195]:39820 "EHLO mail-ua0-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932725AbeGHKtm (ORCPT ); Sun, 8 Jul 2018 06:49:42 -0400 Received: by mail-ua0-f195.google.com with SMTP id n4-v6so10071568uad.6 for ; Sun, 08 Jul 2018 03:49:41 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=l6Xb1ivkbddSChoJrasjZ0NHXotZkPiF0gAy0S/xPfY=; b=d+Zpvp/QcypQV61qlnoc6Jw+UsYNzfUiSIIYutHdrKmliST8ynuwYff5MRlZNbltPY U5SVE6SUGTjgsnDXAhQZueL7f3lNL205skT2RDlVijHottRFDtbJSo3xf5V1pfDTAU8v +dKFyo1ZuQHD9tYBmu2Xfr6Vc9Eoa0z5kTO1ykV8rn5GVgconKj9H0YIc6dnIehPyvdl g8b29hNRqw1YKhQ1q6UP5lSu1NB+4GptkRc+/zZMCgFV+cY2+iX3QHn1DqHVX0ykpZyT EP9dQc6sVvx61ftvzHdk5ASG5cS3lF6zf/HMb165zfaAI1btKbwbHqTXfodbE9mSujAe cdQA== X-Gm-Message-State: APt69E214jLCUInCtydfcumqrlDLWkrpLdqp1pWae8MAP18D6oxskXHR 2xRmMyE+l3j0fhaSWgDRhws+Do2ir19y3Z3Zjj8= X-Google-Smtp-Source: AAOMgpfgkoqNK619apm6x+vWTD7uq3dOrErin9ltGFD1CSbvkIVLRAEVW8Im4BhnK+TU9+0khYra1IhAPESFP5UDtgM= X-Received: by 2002:ab0:25d6:: with SMTP id y22-v6mr11057621uan.33.1531046981370; Sun, 08 Jul 2018 03:49:41 -0700 (PDT) MIME-Version: 1.0 References: <20180619140229.3615110-1-arnd@arndb.de> <20180619140229.3615110-2-arnd@arndb.de> In-Reply-To: From: Geert Uytterhoeven Date: Sun, 8 Jul 2018 12:49:29 +0200 Message-ID: Subject: Re: [PATCH 2/3] [v2] m68k: mac: use time64_t in RTC handling To: Arnd Bergmann Cc: Finn Thain , Paul Mackerras , Michael Ellerman , Joshua Thompson , Mathieu Malaterre , Benjamin Herrenschmidt , Greg Ungerer , linux-m68k , linuxppc-dev , Linux Kernel Mailing List , y2038 Mailman List , Meelis Roos , Andreas Schwab Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Arnd, Finn, On Fri, Jun 22, 2018 at 10:55 AM Arnd Bergmann wrote: > On Fri, Jun 22, 2018 at 7:26 AM, Finn Thain wrote: > > On Tue, 19 Jun 2018, Arnd Bergmann wrote: > > > >> The real-time clock on m68k (and powerpc) mac systems uses an unsigned > >> 32-bit value starting in 1904, which overflows in 2040, about two years > >> later than everyone else, but this gets wrapped around in the Linux code > >> in 2038 already because of the deprecated usage of time_t and/or long in > >> the conversion. > >> > >> Getting rid of the deprecated interfaces makes it work until 2040 as > >> documented, and it could be easily extended by reinterpreting the > >> resulting time64_t as a positive number. For the moment, I'm adding a > >> WARN_ON() that triggers if we encounter a time before 1970 or after 2040 > >> (the two are indistinguishable). > >> > > > > I really don't like the WARN_ON(), but I'd prefer to address that in a > > separate patch rather than impede the progress of this patch (or of this > > series, since 3/3 seems to be unrelated). > > > > BTW, have you considered using the same wrap-around test (i.e. YY < 70) > > that we use for the year register in the other RTC chips? > > That wrap-around test would have the same effect as the my original > version (aside from the two bugs I now fixed), doing rougly > > - return time - RTC_OFFSET; > + return (u32)(time - RTC_OFFSET); > > or some other variation of that will give us an RTC that supports all dates > between 1970 and 2106. I don't think anyone so far had a strong > preference here, so I went with what Mathieu suggested and kept the > original Mac behavior, but added the WARN_ON(). So, is this safe to apply? Especially in light of the warnings seen by Meelis with the PPC version. Thanks! Gr{oetje,eeting}s, Geert -- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that. -- Linus Torvalds