Re: [LTP] [PATCH v2] rtc02: loosen the compare precision with few seconds

Cyril Hrubis
2022-05-10T14:07:01Z

Hi!
> static int rtc_tm_cmp(struct rtc_time *set_tm, struct rtc_time *read_tm)
> {
> - return !((set_tm->tm_sec == read_tm->tm_sec)
> - && (set_tm->tm_min == read_tm->tm_min)
> - && (set_tm->tm_hour == read_tm->tm_hour)
> - && (set_tm->tm_mday == read_tm->tm_mday)
> + long delta, seconds1, seconds2;
> +
> + /*
> + * Convert hour/min/sec into seconds to handle the normal
> + * and special situations:
> + * 1#
> + * set_tm: 2022-04-28 13:00:50
> + * read_tm: 2022-04-28 13:00:50
> + * 2#
> + * set_tm: 2022-04-28 13:00:50
> + * read_tm: 2022-04-28 13:00:51
> + * 3#
> + * set_tm: 2022-04-28 13:00:59
> + * read_tm: 2022-04-28 13:01:00
> + * 4#
> + * set_tm: 2022-04-28 13:59:59
> + * read_tm: 2022-04-28 14:00:00
> + *
> + * Note: as we have avoided testing around the zero
> + * clock, so it's impossible to hit situation 5#
> + * set_tm: 2022-04-28 23:59:59
> + * read_tm: 2022-04-29 00:00:00
> + */
> + if (!(set_tm->tm_sec == read_tm->tm_sec)
> + || !(set_tm->tm_min == read_tm->tm_min)
> + || !(set_tm->tm_hour == read_tm->tm_hour)) {
> +
> + seconds1 = (set_tm->tm_hour * 3600) + (set_tm->tm_min * 60) + set_tm->tm_sec;
> + seconds2 = (read_tm->tm_hour * 3600) + (read_tm->tm_min * 60) + read_tm->tm_sec;
> +
> + delta = seconds2 - seconds1;
> +
> + if (delta < 0 || delta > 3)
> + return 1;
> + }
> +
> + return !((set_tm->tm_mday == read_tm->tm_mday)
> && (set_tm->tm_mon == read_tm->tm_mon)
> && (set_tm->tm_year == read_tm->tm_year));
> }

I would have done this a bit differently, first chek for day, mon, year
then do the calculation as:

if (set_tm->tm_year != read_tm->tm_year)
return 1;

if (set_tm->tm_mon != read_tm->tm_mon)
return 1;

if (set_tm->tm_mday != read_tm->tm_mday)
return 1;

seconds1 = ....
seconds2 = ....
delta = ...

if (delta < 0 || delta > 3)
return 1;

return 0;

I find this a bit clearer to read.

--
Cyril Hrubis
chrubis@suse.cz