linux-kernel - Re: [PATCH 3/3] lib/vsprintf: Add %pC{,n,r} format specifiers for clocks

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Date:	Sat, 28 Feb 2015 15:56:45 +0100
From:	Geert Uytterhoeven <geert@...ux-m68k.org>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Jonathan Corbet <corbet@....net>,
	Mike Turquette <mturquette@...aro.org>,
	Stephen Boyd <sboyd@...eaurora.org>,
	Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>,
	"linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Geert Uytterhoeven <geert+renesas@...der.be>
Subject: Re: [PATCH 3/3] lib/vsprintf: Add %pC{,n,r} format specifiers for clocks

Hi Andrew,

On Fri, Feb 27, 2015 at 11:18 PM, Andrew Morton
<akpm@...ux-foundation.org> wrote:
> On Thu, 26 Feb 2015 12:13:03 +0100 Geert Uytterhoeven <geert@...ux-m68k.org> wrote:
>
>> From: Geert Uytterhoeven <geert+renesas@...der.be>
>>
>> Add format specifiers for printing struct clk:
>>   - '%pC' or '%pCn': name (Common Clock Framework) or address (legacy
>>     clock framework) of the clock,
>>   - '%pCr': rate of the clock.
>>
>> ...
>>
>> +static noinline_for_stack
>> +char *clock(char *buf, char *end, struct clk *clk, struct printf_spec spec,
>> +         const char *fmt)
>> +{
>> +     if (!clk)
>> +             return string(buf, end, NULL, spec);
>> +
>> +     switch (fmt[1]) {
>> +     case 'r':
>> +             return number(buf, end, clk_get_rate(clk), spec);
>> +
>> +     case 'n':
>> +     default:
>> +#ifdef CONFIG_COMMON_CLK
>> +             return string(buf, end, __clk_get_name(clk), spec);
>> +#else
>> +             spec.base = 16;
>> +             spec.field_width = sizeof(unsigned long) * 2 + 2;
>> +             spec.flags |= SPECIAL | SMALL | ZEROPAD;
>> +             return number(buf, end, (unsigned long)clk, spec);
>> +#endif
>> +     }
>> +}
>
> Seems a bit cruel to teeny systems which don't implement clock.  How does
> this look?  Saves 160 bytes in each powerpc build!

> diff -puN lib/vsprintf.c~lib-vsprintf-add-%pcnr-format-specifiers-for-clocks-fix lib/vsprintf.c
> --- a/lib/vsprintf.c~lib-vsprintf-add-%pcnr-format-specifiers-for-clocks-fix
> +++ a/lib/vsprintf.c
> @@ -1320,24 +1320,27 @@ static noinline_for_stack
>  char *clock(char *buf, char *end, struct clk *clk, struct printf_spec spec,
>             const char *fmt)
>  {
> -       if (!clk)
> -               return string(buf, end, NULL, spec);
> +#ifdef CONFIG_HAVE_CLK
> +       if (clk) {

On second thought, you can achieve the same result without #ifdef
with this 2-line change:

-       if (!clk)
+       if (!IS_ENABLED(CONFIG_HAVE_CLK) || !clk)

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds
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