linux-kernel - Re: [PATCH v2] lib/string: update match_string() doc-strings with correct behavior

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Message-ID: <20200213093646.GY10400@smile.fi.intel.com>
Date:   Thu, 13 Feb 2020 11:36:46 +0200
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     Alexandru Ardelean <alexandru.ardelean@...log.com>
Cc:     linux-kernel@...r.kernel.org, akpm@...ux-foundation.org,
        keescook@...omium.org, tobin@...nel.org, gregkh@...uxfoundation.org
Subject: Re: [PATCH v2] lib/string: update match_string() doc-strings with
 correct behavior

On Thu, Feb 13, 2020 at 09:27:22AM +0200, Alexandru Ardelean wrote:
> There were a few attempts at changing behavior of the match_string()
> helpers (i.e. 'match_string()' & 'sysfs_match_string()'), to change &
> extend the behavior according to the doc-string.
> 
> But the simplest approach is to just fix the doc-strings. The current
> behavior is fine as-is, and some bugs were introduced trying to fix it.
> 
> As for extending the behavior, new helpers can always be introduced if
> needed.
> 
> The match_string() helpers behave more like 'strncmp()' in the sense that
> they go up to n elements or until the first NULL element in the array of
> strings.
> 
> This change updates the doc-strings with this info.

Thanks, looks good to me now.
Acked-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>

> 
> Signed-off-by: Alexandru Ardelean <alexandru.ardelean@...log.com>
> ---
>  lib/string.c | 16 ++++++++++++++++
>  1 file changed, 16 insertions(+)
> 
> diff --git a/lib/string.c b/lib/string.c
> index f607b967d978..6012c385fb31 100644
> --- a/lib/string.c
> +++ b/lib/string.c
> @@ -699,6 +699,14 @@ EXPORT_SYMBOL(sysfs_streq);
>   * @n:		number of strings in the array or -1 for NULL terminated arrays
>   * @string:	string to match with
>   *
> + * This routine will look for a string in an array of strings up to the
> + * n-th element in the array or until the first NULL element.
> + *
> + * Historically the value of -1 for @n, was used to search in arrays that
> + * are NULL terminated. However, the function does not make a distinction
> + * when finishing the search: either @n elements have been compared OR
> + * the first NULL element was found.
> + *
>   * Return:
>   * index of a @string in the @array if matches, or %-EINVAL otherwise.
>   */
> @@ -727,6 +735,14 @@ EXPORT_SYMBOL(match_string);
>   *
>   * Returns index of @str in the @array or -EINVAL, just like match_string().
>   * Uses sysfs_streq instead of strcmp for matching.
> + *
> + * This routine will look for a string in an array of strings up to the
> + * n-th element in the array or until the first NULL element.
> + *
> + * Historically the value of -1 for @n, was used to search in arrays that
> + * are NULL terminated. However, the function does not make a distinction
> + * when finishing the search: either @n elements have been compared OR
> + * the first NULL element was found.
>   */
>  int __sysfs_match_string(const char * const *array, size_t n, const char *str)
>  {
> -- 
> 2.20.1
> 

-- 
With Best Regards,
Andy Shevchenko