linux-kernel - Re: [PATCH 1/2] lib: add __sysfs_match_string_with

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Date:   Mon, 22 Apr 2019 11:37:40 +0100
From:   Jonathan Cameron <jic23@...23.retrosnub.co.uk>
To:     Alexandru Ardelean <alexandru.ardelean@...log.com>
Cc:     <linux-iio@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <gregkh@...uxfoundation.org>, <andriy.shevchenko@...ux.intel.com>,
        <namhyung@...nel.org>, <mingo@...nel.org>
Subject: Re: [PATCH 1/2] lib: add __sysfs_match_string_with_gaps() helper

On Mon, 22 Apr 2019 11:32:56 +0300
Alexandru Ardelean <alexandru.ardelean@...log.com> wrote:

> This helper is similar to __sysfs_match_string() with the exception that it
> ignores NULL elements within the array.
> It takes an extra parameter (called `gaps`) which when true will ignore
> the NULL elements. When false, this function behaves exactly like
> `__sysfs_match_string()`.
> 
> Signed-off-by: Alexandru Ardelean <alexandru.ardelean@...log.com>

Hi Alex,

The existence of that gaps parameter does seem a little odd.
Why not just have the exposed _gaps form wrap a version that
takes that parameter and always set it to true?

Otherwise looks good to me.

Jonathan

> ---
>  include/linux/string.h |  9 ++++++++-
>  lib/string.c           | 14 ++++++++++----
>  2 files changed, 18 insertions(+), 5 deletions(-)
> 
> diff --git a/include/linux/string.h b/include/linux/string.h
> index 7927b875f80c..30595ed483dc 100644
> --- a/include/linux/string.h
> +++ b/include/linux/string.h
> @@ -189,7 +189,14 @@ static inline int strtobool(const char *s, bool *res)
>  }
>  
>  int match_string(const char * const *array, size_t n, const char *string);
> -int __sysfs_match_string(const char * const *array, size_t n, const char *s);
> +int __sysfs_match_string_with_gaps(const char * const *array, size_t n,
> +				   const char *str, bool gaps);
> +
> +static inline int __sysfs_match_string(const char * const *array, size_t n,
> +				       const char *str)
> +{
> +	return __sysfs_match_string_with_gaps(array, n, str, false);
> +}
>  
>  /**
>   * sysfs_match_string - matches given string in an array
> diff --git a/lib/string.c b/lib/string.c
> index 38e4ca08e757..8ddac3cd292a 100644
> --- a/lib/string.c
> +++ b/lib/string.c
> @@ -659,30 +659,36 @@ int match_string(const char * const *array, size_t n, const char *string)
>  EXPORT_SYMBOL(match_string);
>  
>  /**
> - * __sysfs_match_string - matches given string in an array
> + * __sysfs_match_string_with_gaps - matches string in array ignoring NULLs
>   * @array: array of strings
>   * @n: number of strings in the array or -1 for NULL terminated arrays
>   * @str: string to match with
> + * @gaps: boolean to ignore NULL elements within the array
>   *
>   * Returns index of @str in the @array or -EINVAL, just like match_string().
>   * Uses sysfs_streq instead of strcmp for matching.
> + * Ignores NULL pointers within the @array if @gaps is true.
>   */
> -int __sysfs_match_string(const char * const *array, size_t n, const char *str)
> +int __sysfs_match_string_with_gaps(const char * const *array, size_t n,
> +				   const char *str, bool gaps)
>  {
>  	const char *item;
>  	int index;
>  
>  	for (index = 0; index < n; index++) {
>  		item = array[index];
> -		if (!item)
> +		if (!item) {
> +			if (gaps)
> +				continue;
>  			break;
> +		}
>  		if (sysfs_streq(item, str))
>  			return index;
>  	}
>  
>  	return -EINVAL;
>  }
> -EXPORT_SYMBOL(__sysfs_match_string);
> +EXPORT_SYMBOL(__sysfs_match_string_with_gaps);
>  
>  #ifndef __HAVE_ARCH_MEMSET
>  /**