linux-kernel - Re: [PATCH v1] lib/vsprintf: update comment about simple

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Date:   Thu, 27 Feb 2020 14:14:28 +0100
From:   Petr Mladek <pmladek@...e.com>
To:     Rasmus Villemoes <linux@...musvillemoes.dk>
Cc:     Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>,
        Andy Shevchenko <andy.shevchenko@...il.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Alexey Dobriyan <adobriyan@...il.com>
Subject: Re: [PATCH v1] lib/vsprintf: update comment about
 simple_strto<foo>() functions

On Sat 2020-02-22 01:28:25, Rasmus Villemoes wrote:
> On 21/02/2020 17.33, Uwe Kleine-König wrote:
> > On Fri, Feb 21, 2020 at 05:27:49PM +0200, Andy Shevchenko wrote:
> >> On Fri, Feb 21, 2020 at 4:54 PM Uwe Kleine-König
> >> <u.kleine-koenig@...gutronix.de> wrote:
> >>> On Fri, Feb 21, 2020 at 10:57:23AM +0200, Andy Shevchenko wrote:
> >>>> The commit 885e68e8b7b1 ("kernel.h: update comment about simple_strto<foo>()
> >>>> functions") updated a comment regard to simple_strto<foo>() functions, but
> >>>> missed similar change in the vsprintf.c module.
> >>>>
> >>>> Update comments in vsprintf.c as well for simple_strto<foo>() functions.
> >>
> >> ...
> >>
> >>>> - * This function is obsolete. Please use kstrtoull instead.
> >>>> + * This function has caveats. Please use kstrtoull instead.
> >>
> >>> I wonder if we instead want to create a set of functions that is
> >>> versatile enough to cover kstrtoull and simple_strtoull. i.e. fix the
> >>> rounding problems (that are the caveats, right?) and as calling
> >>> convention use an errorvalued int return + an output-parameter of the
> >>> corresponding type.
> >>
> >> It wouldn't be possible to apply same rules to both. They both are
> >> part of existing ABI.
> > 
> > The idea is to creat a sane set of functions, then convert all users to
> > the sane one and only then strip the strange functions away. (Userspace)
> > ABI isn't affected, is it?
> 
> There are lots of in-tree users of all these interfaces, converting them
> all is never going to happen. And yes, there are also kstrtox_user
> variants which are definitely part of ABI (more or less the whole reason
> kstrox accepts a single trailing newline but is otherwise rather strict
> is so it can parse stuff that is echo'd to a sysfs/procfs/... file).

Thanks a lot for the detailed answer. It seems that there is no easy
solution to the problem.

Is still anyone against the original patch updating the comments in
vsprintf.c. Otherwise, I would queue it for 5.7.

Best Regards,
Petr