linux-kernel - Re: [PATCH 5/8] lib: bitmap_getnum: separate arg into region and field

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Date:   Tue, 26 Jan 2021 23:23:43 +0200
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     Paul Gortmaker <paul.gortmaker@...driver.com>
Cc:     linux-kernel@...r.kernel.org, lizefan@...wei.com, mingo@...nel.org,
        tglx@...utronix.de, josh@...htriplett.org, yury.norov@...il.com,
        peterz@...radead.org, paulmck@...nel.org, fweisbec@...il.com,
        linux@...musvillemoes.dk
Subject: Re: [PATCH 5/8] lib: bitmap_getnum: separate arg into region and
 field

On Tue, Jan 26, 2021 at 12:11:38PM -0500, Paul Gortmaker wrote:
> The bitmap_getnum is only used on a region's start/end/off/group_len
> field.  Trivially decouple the region from the field so that the region
> pointer is available for a pending change.

Honestly, I don't like this macro trick. It's bad in couple of ways:
 - it hides what actually is done with the fields of r structure
   (after you get that they are fields!)
 - it breaks possibility to compile time (type) checks

I will listen what others say, but I'm in favour not to proceed like this.

> Cc: Yury Norov <yury.norov@...il.com>
> Cc: Rasmus Villemoes <linux@...musvillemoes.dk>
> Cc: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
> Signed-off-by: Paul Gortmaker <paul.gortmaker@...driver.com>
> ---
>  lib/bitmap.c | 9 +++++----
>  1 file changed, 5 insertions(+), 4 deletions(-)
> 
> diff --git a/lib/bitmap.c b/lib/bitmap.c
> index 833f152a2c43..f65be2f148fd 100644
> --- a/lib/bitmap.c
> +++ b/lib/bitmap.c
> @@ -533,6 +533,7 @@ static const char *bitmap_getnum(const char *str, unsigned int *num)
>  	*num = n;
>  	return str + len;
>  }
> +#define bitmap_getrnum(s, r, pos) bitmap_getnum(s, &(r->pos))
>  
>  static inline bool end_of_str(char c)
>  {
> @@ -571,7 +572,7 @@ static const char *bitmap_find_region_reverse(const char *start, const char *end
>  
>  static const char *bitmap_parse_region(const char *str, struct region *r)
>  {
> -	str = bitmap_getnum(str, &r->start);
> +	str = bitmap_getrnum(str, r, start);
>  	if (IS_ERR(str))
>  		return str;
>  
> @@ -581,7 +582,7 @@ static const char *bitmap_parse_region(const char *str, struct region *r)
>  	if (*str != '-')
>  		return ERR_PTR(-EINVAL);
>  
> -	str = bitmap_getnum(str + 1, &r->end);
> +	str = bitmap_getrnum(str + 1, r, end);
>  	if (IS_ERR(str))
>  		return str;
>  
> @@ -591,14 +592,14 @@ static const char *bitmap_parse_region(const char *str, struct region *r)
>  	if (*str != ':')
>  		return ERR_PTR(-EINVAL);
>  
> -	str = bitmap_getnum(str + 1, &r->off);
> +	str = bitmap_getrnum(str + 1, r, off);
>  	if (IS_ERR(str))
>  		return str;
>  
>  	if (*str != '/')
>  		return ERR_PTR(-EINVAL);
>  
> -	return bitmap_getnum(str + 1, &r->group_len);
> +	return bitmap_getrnum(str + 1, r, group_len);
>  
>  no_end:
>  	r->end = r->start;
> -- 
> 2.17.1
> 

-- 
With Best Regards,
Andy Shevchenko