Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Date:   Thu, 3 Oct 2019 14:35:38 +0200
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
Message-ID: <20191003123538.GS4106@piout.net>
References: <20190911154803.15969-1-lukma@denx.de>
 <20191003114831.GR4106@piout.net>
 <20191003142150.3d73a9d7@jawa>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20191003142150.3d73a9d7@jawa>
User-Agent: Mutt/1.12.1 (2019-06-15)
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

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.


-- 
Alexandre Belloni, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com