linux-kernel - Re: [PATCH v1 1/4] lib/vsprintf: Print time64

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Message-ID: <20190726132037.GX9224@smile.fi.intel.com>
Date:   Fri, 26 Jul 2019 16:20:37 +0300
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     Alexandre Belloni <alexandre.belloni@...tlin.com>
Cc:     Petr Mladek <pmladek@...e.com>, linux-kernel@...r.kernel.org,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Hans Verkuil <hverkuil@...all.nl>,
        Mathias Nyman <mathias.nyman@...el.com>,
        Jonathan Corbet <corbet@....net>,
        Thierry Reding <thierry.reding@...il.com>,
        Jonathan Hunter <jonathanh@...dia.com>,
        John Stultz <john.stultz@...aro.org>,
        Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH v1 1/4] lib/vsprintf: Print time64_t in human readable
 format

On Thu, Jan 10, 2019 at 10:58:58PM +0100, Alexandre Belloni wrote:
> On 08/01/2019 16:25:28+0100, Petr Mladek wrote:
> > On Fri 2019-01-04 21:30:06, Andy Shevchenko wrote:
> > > There are users which print time and date represented by content of
> > > time64_t type in human readable format.
> > > 
> > > Instead of open coding that each time introduce %ptT[dt][r] specifier.
> > > 
> > > Few test cases for %ptT specifier has been added as well.

> > > +void time64_to_rtc_time(time64_t time, struct rtc_time *rtc_time)
> > > +{
> > > +#ifdef CONFIG_RTC_LIB
> > > +	rtc_time64_to_tm(time, rtc_time);

> > I wonder if the conversion between struct tm and rtc_time
> > might be useful in general.
> >
> > It might make sense to de-duplicate time64_to_tm() and
> > rtc_time64_to_tm() implementations.

> Looking at 57f1f0874f42, this seemed to be the plan at the time
> time_to_tm was introduced but this was never done. Seeing that tm and
> rtc_time are quite similar, we could probably always use time64_to_tm as
> it is more accurate than rtc_time64_to_tm as the latter assumes a
> specific year range.

So, do I understand correctly that dropping #ifdef along with
rtc_time64_to_tm() call is sufficient for now?

> Maybe be rtc_str should take a struct tm instead of an rtc_time so
> time64_to_rtc_time always uses time64_to_tm.

Because this one, while sounding plausible, maybe too invasive on current
state of affairs.

> > > +#else
> > > +	struct tm tm;
> > > +
> > > +	time64_to_tm(time, 0, &tm);
> > > +
> > > +	rtc_time->tm_sec = tm.tm_sec;
> > > +	rtc_time->tm_min = tm.tm_min;
> > > +	rtc_time->tm_hour = tm.tm_hour;
> > > +	rtc_time->tm_mday = tm.tm_mday;
> > > +	rtc_time->tm_mon = tm.tm_mon;
> > > +	rtc_time->tm_year = tm.tm_year;
> > > +	rtc_time->tm_wday = tm.tm_wday;
> > > +	rtc_time->tm_yday = tm.tm_yday;
> > > +
> > > +	rtc_time->tm_isdst = 0;
> > > +#endif
> > > +}
> > > +
> > > +static noinline_for_stack
> > > +char *time64_str(char *buf, char *end, const time64_t *t, const char *fmt)
> > > +{
> > > +	struct rtc_time tm;
> > > +
> > > +	time64_to_rtc_time(*t, &tm);
> > > +
> > > +	return rtc_str(buf, end, &tm, fmt);
> > > +}

-- 
With Best Regards,
Andy Shevchenko