Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754256AbbFAT7T (ORCPT ); Mon, 1 Jun 2015 15:59:19 -0400 Received: from down.free-electrons.com ([37.187.137.238]:38250 "EHLO mail.free-electrons.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1753631AbbFAT7M (ORCPT ); Mon, 1 Jun 2015 15:59:12 -0400 Date: Mon, 1 Jun 2015 21:59:09 +0200 From: Alexandre Belloni To: Arnd Bergmann Cc: pang.xunlei@zte.com.cn, Alessandro Zummo , Andrew Christian , CIH , John Stultz , linux-kernel@vger.kernel.org, Nicolas Pitre , Xunlei Pang , Richard Purdie , rtc-linux@googlegroups.com, Xunlei Pang Subject: Re: [5/5] drivers/rtc/sa1100: Replace deprecated rtc_tm_to_time() and rtc_time_to_tm() Message-ID: <20150601195909.GO4710@piout.net> References: <1429089611-29776-5-git-send-email-xlpang@126.com> <3404495.679z0IaaBp@wuerfel> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <3404495.679z0IaaBp@wuerfel> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2103 Lines: 55 Hi, On 01/06/2015 at 21:43:22 +0200, Arnd Bergmann wrote : > Note that Alexandre has stepped up as a new maintainer for RTC now, > so whatever he wants is probably the way it should be done. > I'm still quite new in that position and I didn't make my mind in a lot of different topics ;) > I think the way that your first approach came out was a bit unfortunate, > because we didn't have agreement on how it should really be done. > > IMHO the rtc_time64_to_hw32 and rtc_hw32_to_time64 interfaces were a > good concept, most importantly so we can easily find where the potential > problems are, but the implementation was a bit too ambitious in trying > to fix the underlying issue. > > If we want to start this over again, I think a better approach would be > to introduce trivial functions at first, like > > time64_t rtc_hw32_to_time64(u32 hwtime) > { > /* > * this is safe until about 2106, when unsigned u32 seconds from the > * 1970 epoch will overflow > */ > return (u64)hwtime; > } > EXPORT_SYMBOL_GPL(rtc_hw32_to_time64); > > This way, we can fix all the drivers without introducing any possible > ambiguity and later decide how that function should in fact handle the > 2106 overflow. Our grandchildren can take care of that if necessary ;-) > We also have RTCs that can only store the year as an integer between 0 and 99. Some of them will definitively not pass 2099, considering that the can only handle leap days between 2000 and 2099. Also, we have a few drivers assuming that year >= 70 is in the 19s so they will stop working correctly in 2070. I think we also have to consider those while trying to find a solution. I feel that we still have a bit of time before having to hurry and find a proper solution ;) -- Alexandre Belloni, Free Electrons Embedded Linux, Kernel and Android engineering http://free-electrons.com -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/