From: Alexandre Belloni <alexandre.belloni@bootlin.com>
To: Lukasz Majewski <lukma@denx.de>
Cc: Alessandro Zummo <a.zummo@towertech.it>,
linux-rtc@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] rtc: Add support for century bits to m41t62 (rv4162) RTC devices
Date: Thu, 3 Oct 2019 15:43:29 +0200 [thread overview]
Message-ID: <20191003134329.GB575@piout.net> (raw)
In-Reply-To: <20191003151434.49762715@jawa>
On 03/10/2019 15:14:34+0200, Lukasz Majewski wrote:
> Hi Alexandre,
>
> > On 03/10/2019 14:21:50+0200, Lukasz Majewski wrote:
> > > >
> > > > See the datasheet:
> > > >
> > > > "During any year which is a multiple of 4, the RV-4162 RTC will
> > > > automatically insert leap day, February 29. Therefore, the
> > > > application software must correct for this during the exception
> > > > years (2100, 2200, etc.) as noted above."
> > >
> > > I'm wondering what the phrase "application software" means here?
> > >
> > > If it is the userland SW, then we shall at least be able to set
> > > 2099 in this device and then count on software correction.
> > >
> > > If the "application software" is the kernel driver - the date
> > > correction shall be done there (maybe some lookup table?).
> > >
> > > Personally, I do prefer the first option - this means that with this
> > > patch we can set the time to e.g. 2234 year and then rely on
> > > userland software (or libc) to do the correction.
> > >
> >
> > It is not possible to ensure this correction is properly done in
> > software, there is no point in letting the user set those bits.
> >
> >
>
> I see your point.
>
> However, could you share your idea on testing setting RTC time to year
> 2100 on this particular IC (by using hctosys and friends)?
>
You can use rtc from
https://git.kernel.org/pub/scm/linux/kernel/git/abelloni/rtc-tools.git/
You can also use rtc-range with your patch to observe that it fails in
2100.
--
Alexandre Belloni, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com
next prev parent reply other threads:[~2019-10-03 13:43 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-09-11 15:48 [PATCH] rtc: Add support for century bits to m41t62 (rv4162) RTC devices Lukasz Majewski
2019-09-30 7:56 ` Lukasz Majewski
2019-10-03 11:48 ` Alexandre Belloni
2019-10-03 12:21 ` Lukasz Majewski
2019-10-03 12:35 ` Alexandre Belloni
2019-10-03 13:14 ` Lukasz Majewski
2019-10-03 13:43 ` Alexandre Belloni [this message]
2019-10-03 14:10 ` Lukasz Majewski
2019-10-03 14:23 ` Alexandre Belloni
2019-10-03 14:49 ` Lukasz Majewski
2019-10-03 21:34 ` Alexandre Belloni
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