Re: [PATCH 00/51] rtc: stop using rtc deprecated functions

From: Russell King - ARM Linux
Date: Tue Jun 20 2017 - 18:40:01 EST

On Wed, Jun 21, 2017 at 12:00:30AM +0200, Thomas Gleixner wrote:
> 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?
> 2) Deal with creative vendors who have their own idea about the 'start
> of the epoch'
> 3) Add the information of wraparound time to the rtc device which
> needs to be filled in for each device. That way the rtc_***
> accessor functions can deal with them whether they wrap in 2038 or
> 2100 or whatever.
> #3 is the simplest problem of them :)

Well, if there's additional non-volatile storage, you can store
additional information in there, but you still need the RTC
subsystem to be aware that the hardware is only 32-bit capable.

You'd also still need something along the lines I detailed
(redefining what dates the past 32-bit values indicate) to cope
with the RTC being set backwards after the machine thinks (possibly
incorrectly) that the date has jumped forwards.

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