linux-kernel - Re: [PATCH v2 01/21] lib/vsprintf: Print time and date in human readable format via %pt

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Date:   Wed, 21 Feb 2018 15:23:30 +0200
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     Rasmus Villemoes <rasmus.villemoes@...vas.dk>,
        Joe Perches <joe@...ches.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        linux-kernel@...r.kernel.org,
        Alessandro Zummo <a.zummo@...ertech.it>,
        Alexandre Belloni <alexandre.belloni@...e-electrons.com>,
        linux-rtc@...r.kernel.org, Arnd Bergmann <arnd@...db.de>,
        Mark Salyzyn <salyzyn@...roid.com>
Cc:     Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
        Dmitry Torokhov <dmitry.torokhov@...il.com>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        Guan Xuetao <gxt@...c.pku.edu.cn>,
        Ingo Molnar <mingo@...nel.org>,
        Jason Wessel <jason.wessel@...driver.com>,
        Jonathan Corbet <corbet@....net>,
        Jonathan Hunter <jonathanh@...dia.com>,
        Krzysztof Kozlowski <krzk@...nel.org>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Thierry Reding <thierry.reding@...il.com>
Subject: Re: [PATCH v2 01/21] lib/vsprintf: Print time and date in human
 readable format via %pt

On Wed, 2018-02-21 at 08:38 +0100, Rasmus Villemoes wrote:
> On 2018-02-21 00:55, Joe Perches wrote:
> > On Tue, 2018-02-20 at 23:43 +0200, Andy Shevchenko wrote:
> > > There are users which print time and date represented by content
> > > of
> > > struct rtc_time in human readable format.
> > > 
> > > Instead of open coding that each time introduce %ptR[dt][rv]
> > > specifier.
> > > 
> > > Note, users have to select PRINTK_PEXT_TIMEDATE option in a
> > > Kconfig.
> > 
> > Not sure this is a great option.
> > Not just the name, the need to select it.
> 
> Bikeshedding first: If you do keep the config option, please use
> PRINTF,
> not PRINTK - vsprintf can be and is used by lots of code other than
> printk.

OK.

> Well, on the one hand, I like to reduce the size of the kernel when
> possible and ideally make all new functionality guarded by config
> options, but OTOH, how much does compiling out the datetime formatters
> really save?

https://lists.01.org/pipermail/kbuild-all/2017-June/034950.html

I understand that half a year time allows us to increase kernel text
size by 750+ bytes unconditionally.

I would really like to not use any option.

>  Also, I agree with Joe's concern about the need to select
> it.

So, what exactly you are proposing?

>  Maybe if we had a gcc plugin that did %pFOO validation it could also
> warn about %pBAR being used without a corresponding config option
> being
> set. But we don't have that currently...

We have not, so, it's out of scope. If it's a big impediment, then I'm
not the guy who will do the job.

-- 
Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Intel Finland Oy