linux-kernel - Re: [PATCH] lib/string: sysfs_streq works case insensitively

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Message-ID: <CAJX1YtYRK=_X8+mvva2S35-K4kpwXSAGctUJ01TEDFRhS0y5LA@mail.gmail.com>
Date:   Wed, 28 Apr 2021 09:31:55 +0200
From:   Gioh Kim <gi-oh.kim@...os.com>
To:     Andy Shevchenko <andy.shevchenko@...il.com>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: Re: [PATCH] lib/string: sysfs_streq works case insensitively

On Wed, Apr 28, 2021 at 8:42 AM Andy Shevchenko
<andy.shevchenko@...il.com> wrote:
>
>
>
> On Wednesday, April 28, 2021, Gioh Kim <gi-oh.kim@...os.com> wrote:
>>
>> On Mon, Apr 12, 2021 at 1:33 PM Gioh Kim <gi-oh.kim@...os.com> wrote:
>> >
>> > As the name shows, it checks the strings inputed from sysfs.
>> > It should work for both case-sensitive filesystem and
>> > case-insensitive filesystem. Therefore sysfs_streq should work
>> > case-insensitively.
>> >
>> > Signed-off-by: Gioh Kim <gi-oh.kim@...os.com>
>> > ---
>> >  lib/string.c | 6 ++++--
>> >  1 file changed, 4 insertions(+), 2 deletions(-)
>> >
>> > diff --git a/lib/string.c b/lib/string.c
>> > index 7548eb715ddb..d0914dffdaae 100644
>> > --- a/lib/string.c
>> > +++ b/lib/string.c
>> > @@ -688,7 +688,8 @@ EXPORT_SYMBOL(strsep);
>> >  #endif
>> >
>> >  /**
>> > - * sysfs_streq - return true if strings are equal, modulo trailing newline
>> > + * sysfs_streq - return true if strings are equal case-insentively,
>> > + *               modulo trailing newline
>> >   * @s1: one string
>> >   * @s2: another string
>> >   *
>> > @@ -696,10 +697,11 @@ EXPORT_SYMBOL(strsep);
>> >   * NUL and newline-then-NUL as equivalent string terminations.  It's
>> >   * geared for use with sysfs input strings, which generally terminate
>> >   * with newlines but are compared against values without newlines.
>> > + * And case does not matter for the sysfs input strings comparison.
>> >   */
>> >  bool sysfs_streq(const char *s1, const char *s2)
>> >  {
>> > -       while (*s1 && *s1 == *s2) {
>> > +       while (*s1 && tolower(*s1) == tolower(*s2)) {
>> >                 s1++;
>> >                 s2++;
>> >         }
>> > --
>> > 2.25.1
>> >
>>
>> Hi Andrew,
>>
>
> Are you sure it’s good change? Sysfs is used for an ABI and you are opening a can of worms. From me NAK to this change without a very good background description that tells why it is safe to do.

https://www.spinics.net/lists/kernel/msg3898123.html
My initial idea was making a new function: sysfs_streqcase.
Andrew and Greg suggested making sysfs_streq to be case-insensitive.
I would like to have a discussion about it.

>
>
>>
>> I changed sysfs_streq to be case-insensitive as you requested.
>> Is there any progress?
>
>
>
> --
> With Best Regards,
> Andy Shevchenko
>
>