Re: [rtc-linux] Re: [PATCH] rtc-da9063: avoid writing undefined data to rtc

[Alexandre Belloni <alexandre.belloni@free-electrons.com>]

On 27/11/2015 at 16:27:25 +0100, Enrico Scholz wrote :
> > Unfortunately, the datasheets are behind a register wall and I can't
> > check. Is there any meaningful bits mixed in the date/time registers?
> 
> We can set "RTC_EN and CRYSTAL writing disabled" (COUNT_Y[6]) randomly;
> this bit has a different meaning for read ("RTC clock okay") and write
> ("disable writing"; not clearable).
> 
> ALARM_MO[4] "Period of the Tick (0: every second, 1: every minute)" or
> ALARM_Y[7+6] (enable tick/alarm) should not be set randomly either.
> 
> 
> I think, it is always a bad idea to write random data from stack to a
> device.
> 

I agree.

> 
> > I think this was intended to keep those bits to their previous value but
> > this is not yet implemented.
> 
> Datasheet does not say how to deal with "reserved" bits; but it would be
> imo overkill to apply a regmap_update_bits() like access to the RTC
> registers.
> 

It depends on how much you care about those bits across reboots.

I'll take your patch anyway, unless Steve has another opinion on that.


-- 
Alexandre Belloni, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com

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