linux-kernel - Re: [PATCH][next] scsi: arcmsr: remove redundant check for secs

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Date:   Fri, 15 Dec 2017 18:52:44 +0100
From:   walter harms <wharms@....de>
To:     Colin King <colin.king@...onical.com>
CC:     "James E . J . Bottomley" <jejb@...ux.vnet.ibm.com>,
        "Martin K . Petersen" <martin.petersen@...cle.com>,
        Ching Huang <ching2048@...ca.com.tw>,
        linux-scsi@...r.kernel.org, kernel-janitors@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH][next] scsi: arcmsr: remove redundant check for secs <
 0



Am 09.12.2017 01:34, schrieb Colin King:
> From: Colin Ian King <colin.king@...onical.com>
> 
> The check for secs being less than zero is redundant for two reasons.
> Firstly, secs is unsigned so the check is always going to be false.
> Secondly, if secs was signed the proceeding calculation of secs is
> never going to be negative.  Hence we can remove this redundant check
> and day and secs re-adjustment.
> 
> Detected by static analysis with smatch:
> arcmsr_set_iop_datetime() warn: unsigned 'secs' is never less than zero.
> 
> Signed-off-by: Colin Ian King <colin.king@...onical.com>
> ---
>  drivers/scsi/arcmsr/arcmsr_hba.c | 4 ----
>  1 file changed, 4 deletions(-)
> 
> diff --git a/drivers/scsi/arcmsr/arcmsr_hba.c b/drivers/scsi/arcmsr/arcmsr_hba.c
> index 0707a60bf5c0..e4258b69f4be 100644
> --- a/drivers/scsi/arcmsr/arcmsr_hba.c
> +++ b/drivers/scsi/arcmsr/arcmsr_hba.c
> @@ -3679,10 +3679,6 @@ static void arcmsr_set_iop_datetime(struct timer_list *t)
>  	secs = (u32)(tv.tv_sec - (sys_tz.tz_minuteswest * 60));
>  	days = secs / 86400;
>  	secs = secs - 86400 * days;

mmh, what they want to do is:
	secs = secs % 86400 ;

> -	if (secs < 0) {
> -		days = days - 1;
> -		secs = secs + 86400;
> -	}
>  	j = days / 146097;
>  	i = days - 146097 * j;
>  	a = i + 719468;

see above.
btw: are the numbers documented ?

re,
 wh