linux-kernel - Re: [PATCH 4/5] drivers/rtc/pl030: Replace deprecated rtc_tm_to_time() and rtc_time_to

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Message-ID: <20150415093510.GW12732@n2100.arm.linux.org.uk>
Date:	Wed, 15 Apr 2015 10:35:10 +0100
From:	Russell King - ARM Linux <linux@....linux.org.uk>
To:	Xunlei Pang <xlpang@....com>
Cc:	linux-kernel@...r.kernel.org, rtc-linux@...glegroups.com,
	Alessandro Zummo <a.zummo@...ertech.it>,
	John Stultz <john.stultz@...aro.org>,
	Arnd Bergmann <arnd@...db.de>,
	Xunlei Pang <pang.xunlei@...aro.org>
Subject: Re: [PATCH 4/5] drivers/rtc/pl030: Replace deprecated
 rtc_tm_to_time() and rtc_time_to_tm()

On Wed, Apr 15, 2015 at 05:20:10PM +0800, Xunlei Pang wrote:
> From: Xunlei Pang <pang.xunlei@...aro.org>
> 
> The driver uses deprecated rtc_tm_to_time() and rtc_time_to_tm(),
> which will overflow in year 2106 on 32-bit machines.
> 
> This patch solves this by:
>  - Replacing rtc_tm_to_time() with rtc_tm_to_time64()
>  - Replacing rtc_time_to_tm() with rtc_time64_to_tm()
> 
> Cc: Russell King <rmk+kernel@....linux.org.uk>
> Signed-off-by: Xunlei Pang <pang.xunlei@...aro.org>

NAK.

How does this fix anything?  The RTC contains 32-bit registers.  Even
if you convert the struct tm to a 64-bit time, you can only write the
lowest 32-bits to the hardware.  You can onyl read the lowest 32-bits
from the hardware too.

This patch solves /nothing/.  In fact, it hides the fact that this RTC
is unable to represent dates after 2106.

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