linux-kernel - Re: [PATCH][V4] lib: fix __sysfs_match

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Date:   Tue, 25 Jun 2019 12:42:41 -0700
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc:     Alexandru Ardelean <alexandru.ardelean@...log.com>,
        linux-kernel@...r.kernel.org, gregkh@...uxfoundation.org,
        alexander.shishkin@...ux.intel.com, ndesaulniers@...gle.com
Subject: Re: [PATCH][V4] lib: fix __sysfs_match_string() helper when n != -1

On Tue, 25 Jun 2019 16:28:12 +0300 Andy Shevchenko <andriy.shevchenko@...ux.intel.com> wrote:

> On Tue, Jun 25, 2019 at 04:01:04PM +0300, Alexandru Ardelean wrote:
> > The documentation the `__sysfs_match_string()` helper mentions that `n`
> > (the size of the given array) should be:
> >  * @n: number of strings in the array or -1 for NULL terminated arrays
> > 
> > The behavior of the function is different, in the sense that it exits on
> > the first NULL element in the array.
> > 
> > This patch changes the behavior, to exit the loop when a NULL element is
> > found, and the size of the array is provided as -1.
> > 
> > All current users of __sysfs_match_string() & sysfs_match_string() provide
> > contiguous arrays of strings, so this behavior change doesn't influence
> > anything (at this point in time).
> > 
> > This behavior change allows for an array of strings to have NULL elements
> > within the array, which will be ignored. This is particularly useful when
> > creating mapping of strings and integers (as bitfields or other HW
> > description).
> 
> Since it does nothing for current users and comes without an example,
> it's hard to justify the need.

Presumably "split this patch away from series" means there's some code
which uses this.  A reference to this in the changelog would be good.

> The code itself looks good to me.

Sure.  But the kerneldoc description of __sysfs_match_string() could do
with an update.