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From: Pavel Machek <pavel-+ZI9xUNit7I@public.gmane.org>
To: Thomas Gleixner <tglx-hfZtesqFncYOwBW4kG4KsQ@public.gmane.org>
Cc: Alexandre Belloni
	<alexandre.belloni-wi1+55ScJUtKEb57/3fJTNBPR1lH4CV8@public.gmane.org>,
	Russell King - ARM Linux
	<linux-I+IVW8TIWO2tmTQ+vhA3Yw@public.gmane.org>,
	Benjamin Gaignard
	<benjamin.gaignard-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>,
	Baruch Siach <baruch-NswTu9S1W3P6gbPvEgmw2w@public.gmane.org>,
	"patches-yzvPICuk2AATkU/dhu1WVueM+bqZidxxQQ4Iyu8u01E@public.gmane.org"
	<patches-yzvPICuk2AATkU/dhu1WVueM+bqZidxxQQ4Iyu8u01E@public.gmane.org>,
	Linus Walleij
	<linus.walleij-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>,
	"linux-tegra-u79uwXL29TY76Z2rM5mHXA@public.gmane.org"
	<linux-tegra-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>,
	Thierry Reding
	<thierry.reding-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>,
	"x86-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org"
	<x86-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>,
	Jonathan Hunter
	<jonathanh-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org>,
	Chen-Yu Tsai <wens-jdAy2FN1RRM@public.gmane.org>,
	Ingo Molnar <mingo-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>,
	Sylvain Lemieux
	<slemieux.tyco-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>,
	Sebastian Hesselbarth
	<sebastian.hesselbarth-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>,
	Len Brown <len.brown-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>,
	"linaro-kernel-cunTk1MwBs8s++Sfvej+rw@public.gmane.org"
	<linaro-kernel-cunTk1MwBs8s++Sfvej+rw@public.gmane.org>,
	Jason Cooper <jason-NLaQJdtUoK4Be96aLqz0jA@public.gmane.org>,
	"rtc-linux-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org"
	<rtc-linux-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org>,
	"linux-pm-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" <lin
Subject: Re: [PATCH 00/51] rtc: stop using rtc deprecated functions
Date: Wed, 21 Jun 2017 09:51:52 +0200	[thread overview]
Message-ID: <20170621075152.GA15996@amd> (raw)
In-Reply-To: <alpine.DEB.2.20.1706202343120.2157@nanos>

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Hi!

> > I agree with that but not the android guys. They seem to mandate an RTC
> > that can store time from 01/01/1970. I don't know much more than that
> > because they never cared to explain why that was actually necessary
> > (apart from a laconic "this will result in a bad user experience")
> > 
> > I think tglx had a plan for offsetting the time at some point so 32-bit
> > platform can pass 2038 properly.
> 
> Yes, but there are still quite some issues to solve there:
> 
>      1) How do you tell the system that it should apply the offset in the
>      	first place, i.e at boot time before NTP or any other mechanism can
>      	correct it?

I'd not do offset. Instead, I'd select a threshold (perhaps year of
release of given kernel?) and

	if (rtc_time < year_of_release_of_kernel)
	   rtc_time += 0x100000000;

Ok, we'll have to move away from "rtc_time == 0 indicates zero", as
seen in some drivers.

>      2) Deal with creative vendors who have their own idea about the 'start
>      	of the epoch'

If someone uses different threshold, well, there will be
confusion. But only for users that have their rtc set to the past,
which is quite unusual.

									Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

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  parent reply	other threads:[~2017-06-21  7:51 UTC|newest]

Thread overview: 25+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-06-20 21:35 [PATCH 00/51] rtc: stop using rtc deprecated functions Alexandre Belloni
     [not found] ` <20170620213507.urobmtg34vzubrdq-m++hUPXGwpdeoWH0uzbU5w@public.gmane.org>
2017-06-20 22:00   ` Thomas Gleixner
2017-06-20 22:38     ` Russell King - ARM Linux
2017-06-21  7:51     ` Pavel Machek [this message]
2017-06-21  8:39       ` Alexandre Belloni
     [not found]         ` <20170621083907.y3gadsmsoufa5niv-m++hUPXGwpdeoWH0uzbU5w@public.gmane.org>
2017-06-21  6:34           ` Pavel Machek
2017-06-21 12:35             ` Alexandre Belloni
     [not found]               ` <20170621123535.b5fvwlydfhnhuqll-m++hUPXGwpdeoWH0uzbU5w@public.gmane.org>
2017-06-21 18:08                 ` Pavel Machek
2017-06-21  9:19           ` Russell King - ARM Linux
     [not found]             ` <20170621091948.GP4902-l+eeeJia6m9URfEZ8mYm6t73F7V6hmMc@public.gmane.org>
2017-06-21  9:41               ` Alexandre Belloni
  -- strict thread matches above, loose matches on Subject: below --
2017-06-20  9:35 Benjamin Gaignard
     [not found] ` <1497951359-13334-1-git-send-email-benjamin.gaignard-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>
2017-06-20 10:03   ` Alexandre Belloni
     [not found]     ` <20170620100348.zh4ygvjjgnhxvmvl-m++hUPXGwpdeoWH0uzbU5w@public.gmane.org>
2017-06-20 10:07       ` Alexandre Belloni
2017-06-20 12:10       ` Pavel Machek
2017-06-20 12:24         ` Alexandre Belloni
     [not found]           ` <20170620122400.sm7qqvwyj6cuzarw-m++hUPXGwpdeoWH0uzbU5w@public.gmane.org>
2017-06-20 13:26             ` Pavel Machek
2017-06-20 13:37               ` Steve Twiss
     [not found]                 ` <6ED8E3B22081A4459DAC7699F3695FB7018CD96FCD-68WUHU125fLzLL1Oxlh9IgLouzNaz+3S@public.gmane.org>
2017-06-20 13:44                   ` Pavel Machek
2017-06-20 13:48                     ` Alexandre Belloni
     [not found]                       ` <20170620134827.ubvzhh25klaotupv-m++hUPXGwpdeoWH0uzbU5w@public.gmane.org>
2017-06-20 15:07                         ` Benjamin Gaignard
     [not found]                           ` <CA+M3ks68+z6nDtYM8CDpso7SxjB6Nt5E=rOc1yxx=kDz6PUeVQ-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2017-06-20 21:15                             ` Russell King - ARM Linux
     [not found]                               ` <20170620211536.GM4902-l+eeeJia6m9URfEZ8mYm6t73F7V6hmMc@public.gmane.org>
2017-06-21  9:26                                 ` David Laight
     [not found]                                   ` <063D6719AE5E284EB5DD2968C1650D6DD00278C0-VkEWCZq2GCInGFn1LkZF6NBPR1lH4CV8@public.gmane.org>
2017-06-21  9:35                                     ` Russell King - ARM Linux
2017-06-20 22:08                             ` Pavel Machek
2017-06-21  9:14                               ` Benjamin Gaignard

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