linux-kernel - Re: [PATCH v3 2/4] staging: exfat: drop duplicate date_time

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Date:   Sun, 8 Sep 2019 19:40:23 +0000
From:   Valentin Vidić <vvidic@...entin-vidic.from.hr>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     devel@...verdev.osuosl.org,
        Valdis Kletnieks <valdis.kletnieks@...edu>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 2/4] staging: exfat: drop duplicate date_time_t struct

On Sun, Sep 08, 2019 at 07:50:31PM +0100, Greg Kroah-Hartman wrote:
> Wait, how are these "duplicate"?  The fields are in different order,
> don't these refer to things on-disk?

On-disk combines the values from these structures in a different form:

          offset  bits
DoubleSeconds  0  5
Minute         5  6
Hour          11  5
Day           16  5
Month         21  4
Year          25  7

> Did you test this?

Just compile tested for now.

> > -struct date_time_t {
> > -	u16      Year;
> > -	u16      Month;
> > -	u16      Day;
> > -	u16      Hour;
> > -	u16      Minute;
> > -	u16      Second;
> > -	u16      MilliSecond;
> > -};
> > -
> >  struct part_info_t {
> >  	u32      Offset;    /* start sector number of the partition */
> >  	u32      Size;      /* in sectors */
> > @@ -289,6 +279,16 @@ struct file_id_t {
> >  	u32      hint_last_clu;
> >  };
> >  
> > +struct timestamp_t {
> > +	u16      millisec;   /* 0 ~ 999              */
> > +	u16      sec;        /* 0 ~ 59               */
> > +	u16      min;        /* 0 ~ 59               */
> > +	u16      hour;       /* 0 ~ 23               */
> > +	u16      day;        /* 1 ~ 31               */
> > +	u16      mon;        /* 1 ~ 12               */
> > +	u16      year;       /* 0 ~ 127 (since 1980) */
> > +};
> 
> They really look "backwards" to me, how are these the same?  What am I
> missing?

date_time_t was only used in a few functions and there was a lot of
copying of the same fields between the two structs. Also some code was
duplicated to do the same thing for each of the structs.

-- 
Valentin