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

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Date:   Mon, 22 Apr 2019 11:16:23 +0000
From:   "Ardelean, Alexandru" <alexandru.Ardelean@...log.com>
To:     "jic23@...23.retrosnub.co.uk" <jic23@...23.retrosnub.co.uk>
CC:     "namhyung@...nel.org" <namhyung@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "andriy.shevchenko@...ux.intel.com" 
        <andriy.shevchenko@...ux.intel.com>,
        "linux-iio@...r.kernel.org" <linux-iio@...r.kernel.org>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        "mingo@...nel.org" <mingo@...nel.org>
Subject: Re: [PATCH 1/2] lib: add __sysfs_match_string_with_gaps() helper

On Mon, 2019-04-22 at 11:37 +0100, Jonathan Cameron wrote:
> [External]
> 
> 
> 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?
> 

That was one way I thought about doing it.
I was thinking about maybe not exporting too many symbols, since that can
add some size-overhead to the kernel during linking.

I'll send a V2.

Thanks
Alex

> 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
> >  /**
> 
>