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

[Cyril Hrubis <chrubis@suse.cz>]

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

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