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Date:   Thu, 18 Aug 2022 21:48:28 +0200
From:   Marek =?UTF-8?B?QmVow7pu?= <kabel@kernel.org>
To:     Andy Shevchenko <andy.shevchenko@gmail.com>
Cc:     Vinod Koul <vkoul@kernel.org>,
        Kishon Vijay Abraham I <kishon@ti.com>,
        Linux Phy <linux-phy@lists.infradead.org>,
        Kees Cook <keescook@chromium.org>,
        Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
        Daniel Scally <djrscally@gmail.com>,
        Gregory Clement <gregory.clement@bootlin.com>,
        Heikki Krogerus <heikki.krogerus@linux.intel.com>,
        Sakari Ailus <sakari.ailus@linux.intel.com>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Pali =?UTF-8?B?Um9ow6Fy?= <pali@kernel.org>,
        josef.schlehofer@nic.cz
Subject: Re: [PATCH linux-phy v2 1/4] string.h: Add str_has_proper_prefix()
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On Thu, 18 Aug 2022 22:10:58 +0300
Andy Shevchenko <andy.shevchenko@gmail.com> wrote:

> On Wed, Aug 17, 2022 at 11:06 PM Marek Beh=C3=BAn <kabel@kernel.org> wrot=
e:
> >
> > Add str_has_proper_prefix(), similar to str_has_prefix(), but requires
> > that the prefix is proper: the string itself must be longer than the
> > prefix.
> >
> > Signed-off-by: Marek Beh=C3=BAn <kabel@kernel.org>
> > ---
> > Andy, Kees, could you ack this if it is ok? =20
>=20
> Seems to me there are too many strlen():s. One is hidden in strncmp().

I thought this was ok cause gcc has optimizations for this in
https://github.com/gcc-mirror/gcc/blob/master/gcc/tree-ssa-strlen.cc

But now I see that kernel does not declare these functions as inline
that call __builtin_strlen()... so probably the optimizations are not
used.

> Besides not the good naming (what 'proper' means),

The naming comes from similar naming in math: proper subset is as
subset that is not equal to the superset. See
https://en.wikipedia.org/wiki/Substring :
  "A proper prefix of a string is not equal to the string itself"

> the entire function is not needed. You may simply call
>=20
>   str_has_prefix() && p[len] !=3D '\0';
>=20
> Correct?

Do you mean that I should implement this function to simply return
  str_has_prefix() && p[len] !=3D '\0'
or that this function should not exist at all and I should do that in
the code where I would have used the function?

Thanks.

Marek