linux-kernel - Re: [PATCH] RTC: RK808: Work around hardware bug on November 31st

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Date:	Fri, 4 Dec 2015 17:54:40 -0800
From:	Julius Werner <jwerner@...omium.org>
To:	Doug Anderson <dianders@...omium.org>
Cc:	Julius Werner <jwerner@...omium.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Alessandro Zummo <a.zummo@...ertech.it>,
	Sonny Rao <sonnyrao@...omium.org>,
	Chris Zhong <zyw@...k-chips.com>,
	Heiko Stuebner <heiko@...ech.de>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	rtc-linux@...glegroups.com
Subject: Re: [PATCH] RTC: RK808: Work around hardware bug on November 31st

> How would such a hook work?  If userspace sees the system suspend on
> Nov 30th and sees the system wake up on Dec 1st, how does it know
> whether it should adjust?  If it's truly Dec 1st then the kernel will
> have adjusted the date from Nov 31st to Dec 1st.  If it's truly Dec
> 2nd then the kernel will not have adjusted the date and the RTC will
> have ticked past Nov 31 and onto Dec 1st.  Userspace can't tell.
> Userspace could try to parse "dmesg" and look to see if the kernel
> adjusted, but that's ugly.

Good point, I didn't think that through far enough. I guess parsing
dmesg would be an option, but a pretty ugly one and it wouldn't be
guaranteed to work if you got an early boot kernel crash after the
correction. So, really, it seems like there's no reliable way to fix
this for S5 (unless we start doing crazy things like writing to disk
from kernel code).
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