linux-kernel - Re: [PATCH 2/4] rtc: digicolor: set range

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Message-ID: <20190430114702.GD11339@piout.net>
Date:   Tue, 30 Apr 2019 13:47:02 +0200
From:   Alexandre Belloni <alexandre.belloni@...tlin.com>
To:     Baruch Siach <baruch@...s.co.il>
Cc:     linux-rtc@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 2/4] rtc: digicolor: set range

On 30/04/2019 14:36:24+0300, Baruch Siach wrote:
> Hi Alexandre,
> 
> On Tue, Apr 30 2019, Alexandre Belloni wrote:
> 
> > While the range of REFERENCE + TIME is actually 33 bits, the counter
> > itself (TIME) is a 32-bits seconds counter.
> >
> > Signed-off-by: Alexandre Belloni <alexandre.belloni@...tlin.com>
> > ---
> >  drivers/rtc/rtc-digicolor.c | 1 +
> >  1 file changed, 1 insertion(+)
> >
> > diff --git a/drivers/rtc/rtc-digicolor.c b/drivers/rtc/rtc-digicolor.c
> > index 5bb14c56bc9a..e6e16aaac254 100644
> > --- a/drivers/rtc/rtc-digicolor.c
> > +++ b/drivers/rtc/rtc-digicolor.c
> > @@ -206,6 +206,7 @@ static int __init dc_rtc_probe(struct platform_device *pdev)
> >  	platform_set_drvdata(pdev, rtc);
> >  
> >  	rtc->rtc_dev->ops = &dc_rtc_ops;
> > +	rtc->rtc_dev->range_max = U32_MAX;
> 
> Where can I find documentation on the meaning and usage of the range_max
> value? I could not find anything in the kernel source.
> 

It should be set to the maximum UNIX timestamp the RTC can be set to
while keeping range_min to range_max contiguous.

In the digicolor case, you could go up to 8589934590 (Wed Mar 16
12:56:30 UTC 2242) but the driver only writes DC_RTC_REFERENCE and I'm
not sure it can also update DC_RTC_TIME safely.

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