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References: <20190729151505.9660-1-hslester96@gmail.com> <5dee05d6cb8498b3e636f5e8a62da673334cb5a9.camel@perches.com>
In-Reply-To: <5dee05d6cb8498b3e636f5e8a62da673334cb5a9.camel@perches.com>
From:   Chuhong Yuan <hslester96@gmail.com>
Date:   Thu, 1 Aug 2019 23:23:33 +0800
Message-ID: <CANhBUQ2RD065Dn8eGkbzSQxfie5XrR_kgaFQ1QgOS4cKNhAfPA@mail.gmail.com>
Subject: Re: [PATCH 08/12] printk: Replace strncmp with str_has_prefix
To:     Joe Perches <joe@perches.com>
Cc:     Petr Mladek <pmladek@suse.com>,
        Sergey Senozhatsky <sergey.senozhatsky@gmail.com>,
        Steven Rostedt <rostedt@goodmis.org>,
        LKML <linux-kernel@vger.kernel.org>
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Joe Perches <joe@perches.com> =E4=BA=8E2019=E5=B9=B47=E6=9C=8830=E6=97=A5=
=E5=91=A8=E4=BA=8C =E4=B8=8A=E5=8D=888:16=E5=86=99=E9=81=93=EF=BC=9A
>
> On Mon, 2019-07-29 at 23:15 +0800, Chuhong Yuan wrote:
> > strncmp(str, const, len) is error-prone.
> > We had better use newly introduced
> > str_has_prefix() instead of it.
> []
> > diff --git a/kernel/printk/braille.c b/kernel/printk/braille.c
> []
> > @@ -11,10 +11,10 @@
> >
> >  int _braille_console_setup(char **str, char **brl_options)
> >  {
> > -     if (!strncmp(*str, "brl,", 4)) {
> > +     if (str_has_prefix(*str, "brl,")) {
> >               *brl_options =3D "";
> >               *str +=3D 4;
> > -     } else if (!strncmp(*str, "brl=3D", 4)) {
> > +     } else if (str_has_prefix(*str, "brl=3D")) {
> >               *brl_options =3D *str + 4;
>
> Better to get rid of the +=3D 4 uses too by storing the result
> of str_has_prefix and using that as the addend.
>
> Perhaps
>         size_t len;
>
>         if ((len =3D str_has_prefix(*str, "brl,"))) {
>                 *brl_options =3D "";
>                 *str +=3D len;
>         } else if ((len =3D str_has_prefix(*str, "brl=3D"))) {
>                 etc...
>

I find that checkpatch.pl forbids assignment in if condition.
So this seems to be infeasible...

> >               *str =3D strchr(*brl_options, ',');
> >               if (!*str) {
> > diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
> []
> > @@ -121,13 +121,13 @@ static int __control_devkmsg(char *str)
> >       if (!str)
> >               return -EINVAL;
> >
> > -     if (!strncmp(str, "on", 2)) {
> > +     if (str_has_prefix(str, "on")) {
> >               devkmsg_log =3D DEVKMSG_LOG_MASK_ON;
> >               return 2;
> > -     } else if (!strncmp(str, "off", 3)) {
> > +     } else if (str_has_prefix(str, "off")) {
> >               devkmsg_log =3D DEVKMSG_LOG_MASK_OFF;
> >               return 3;
> > -     } else if (!strncmp(str, "ratelimit", 9)) {
> > +     } else if (str_has_prefix(str, "ratelimit")) {
> >               devkmsg_log =3D DEVKMSG_LOG_MASK_DEFAULT;
> >               return 9;
> >       }
>
> here too.
>
>