linux-kernel - Re: [PATCH v4 1/5] rtc: Make rtc_time64_to

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Message-ID: <yjymcsje4z5c2htgefya2cocyx5guvepng756vdigjmvxvk6dv@wqyeh33mfty4>
Date: Tue, 6 May 2025 09:58:28 +0200
From: Uwe Kleine-König <u.kleine-koenig@...libre.com>
To: Alexandre Belloni <alexandre.belloni@...tlin.com>
Cc: Alexandre Mergnat <amergnat@...libre.com>, 
	Baolin Wang <baolin.wang@...ux.alibaba.com>, linux-rtc@...r.kernel.org, linux-kernel@...r.kernel.org, 
	AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>, Macpaul Lin <macpaul.lin@...iatek.com>
Subject: Re: [PATCH v4 1/5] rtc: Make rtc_time64_to_tm() support dates before
 1970

Hello Alexandre,

On Mon, Apr 28, 2025 at 06:59:33PM +0200, Uwe Kleine-König wrote:
> On Mon, Apr 28, 2025 at 12:06:47PM +0200, Alexandre Mergnat wrote:
> > Conversion of dates before 1970 is still relevant today because these
> > dates are reused on some hardwares to store dates bigger than the
> > maximal date that is representable in the device's native format.
> > This prominently and very soon affects the hardware covered by the
> > rtc-mt6397 driver that can only natively store dates in the interval
> > 1900-01-01 up to 2027-12-31. So to store the date 2028-01-01 00:00:00
> > to such a device, rtc_time64_to_tm() must do the right thing for
> > time=-2208988800.
> > 
> > Signed-off-by: Alexandre Mergnat <amergnat@...libre.com>
> 
> Given this problem starts to bite in 2028 I'd like to see this (and the
> next) patch backported to stable. If you want a Fixes: line, maybe
> 34bbdc12d04e ("rtc: mt6359: Add RTC hardware range and add support for
> start-year") is sensible here as this is the commit that introduced the
> requirement to handle negative timestamps. (The drivers that made use
> of the offset feature already before that commit all had
> .range_min >= 0, and so are not affected by this problem.)

Given that we're already at v6.15-rc5 I wonder if there is a chance to
get these changes reviewed and applied before v6.15. Would a pull
request help you? If yes, should it only contain the fixes, or also the
updated tests?

Best regards
Uwe

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