linux-kernel - Re: [PATCH v2 09/11] lib/vsprintf: use precision field with %pl[From[To]]

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Date:	Mon, 18 Jan 2016 23:21:07 +0100
From:	Rasmus Villemoes <linux@...musvillemoes.dk>
To:	Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc:	Robert Elliott <elliott@....com>,
	Matt Fleming <matt@...eblueprint.co.uk>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>, linux-kernel@...r.kernel.org,
	Brian Norris <computersforpeace@...il.com>,
	Hariprasad S <hariprasad@...lsio.com>
Subject: Re: [PATCH v2 09/11] lib/vsprintf: use precision field with %pl[From[To]]

On Thu, Jan 14 2016, Andy Shevchenko <andriy.shevchenko@...ux.intel.com> wrote:

> The precision field defines how many digits after period ('.') will be
> printed.

Yuck again.

Didn't you notice gcc barking at you?

warning: precision used with ‘%p’ gnu_printf format [-Wformat=]

So I don't think this will ever be used. 

> Signed-off-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
> ---
>  Documentation/printk-formats.txt |  7 +++++++
>  lib/test_printf.c                | 29 +++++++++++++++++++++++++++++
>  lib/vsprintf.c                   | 20 +++++++++++++++++++-
>  3 files changed, 55 insertions(+), 1 deletion(-)
>
> diff --git a/Documentation/printk-formats.txt b/Documentation/printk-formats.txt
> index 3b41899..534407c 100644
> --- a/Documentation/printk-formats.txt
> +++ b/Documentation/printk-formats.txt
> @@ -295,11 +295,18 @@ unsigned long long value in human-readable form (with IEC binary prefix):
>  	%pl		1048575 B	(1048575)
>  	%plKM		1023 KiB	(1048575)
>  	%pl		1 MiB		(1048576)
> +	%.1plKM		1046527.9 MiB	(1097364144125)
>  	%plG		2 TiB		(2199023255552)
>  
>  	For printing given unsigned long long value in human-readable form with
>  	automatically choosen IEC binary prefix.
>  
> +	Precision, if passed, defines how many digits will be printed after
> +	period ('.'). In this case the biggest possible unit is used in the
> +	given range [From[To]]. The printed value isn't rounded anyhow.
> +
> +	For other use cases consider to call string_get_size().
> +
>  	Passed by reference.
>  
>  bitmap and its derivatives such as cpumask and nodemask:
> diff --git a/lib/test_printf.c b/lib/test_printf.c
> index ae35885..4a2e30b 100644
> --- a/lib/test_printf.c
> +++ b/lib/test_printf.c
> @@ -435,6 +435,30 @@ human_readable(void)
>  		{ .v = 1048575ULL,		.r = "1023 KiB" },
>  		{ .v = 1047552ULL,		.r = "1023 KiB" },
>  	};
> +	struct hr_test_data htdpl0KM[] = {
> +		{ .v = 1097364144128ULL,	.r = "1046528 MiB" },
> +		{ .v = 1097364144125ULL,	.r = "1046527 MiB" },
> +		{ .v = 1048578ULL,		.r = "1 MiB" },
> +		{ .v = 1048576ULL,		.r = "1 MiB" },
> +		{ .v = 1048575ULL,		.r = "1023 KiB" },
> +		{ .v = 1047552ULL,		.r = "1023 KiB" },
> +	};
> +	struct hr_test_data htdpl1KM[] = {
> +		{ .v = 1097364144128ULL,	.r = "1046528.0 MiB" },
> +		{ .v = 1097364144125ULL,	.r = "1046527.9 MiB" },
> +		{ .v = 1048578ULL,		.r = "1.0 MiB" },
> +		{ .v = 1048576ULL,		.r = "1.0 MiB" },
> +		{ .v = 1048575ULL,		.r = "1023.9 KiB" },
> +		{ .v = 1047552ULL,		.r = "1023.0 KiB" },
> +	};
> +	struct hr_test_data htdpl3KM[] = {
> +		{ .v = 1097364144128ULL,	.r = "1046528.000 MiB" },
> +		{ .v = 1097364144125ULL,	.r = "1046527.999 MiB" },
> +		{ .v = 1048578ULL,		.r = "1.000 MiB" },
> +		{ .v = 1048576ULL,		.r = "1.000 MiB" },
> +		{ .v = 1048575ULL,		.r = "1023.999 KiB" },
> +		{ .v = 1047552ULL,		.r = "1023.000 KiB" },
> +	};
>  	struct hr_test_array {
>  		const char *fmt;
>  		struct hr_test_data *data;
> @@ -446,6 +470,11 @@ human_readable(void)
>  		{ "%plKM",	htdplKM,	ARRAY_SIZE(htdplKM) },
>  		/* No reversed %pl[To[From]] order */
>  		{ "%plMK",	htdplM,		ARRAY_SIZE(htdplM) },
> +		{ "%.0plKM",	htdpl0KM,	ARRAY_SIZE(htdpl0KM) },
> +		{ "%.1plKM",	htdpl1KM,	ARRAY_SIZE(htdpl1KM) },
> +		{ "%.3plKM",	htdpl3KM,	ARRAY_SIZE(htdpl3KM) },
> +		/* For now precision is in range [0..3] */
> +		{ "%.4plKM",	htdplKM,	ARRAY_SIZE(htdplKM) },
>  	};
>  	unsigned int i, j;
>  
> diff --git a/lib/vsprintf.c b/lib/vsprintf.c
> index fbcb221..2dd86c9 100644
> --- a/lib/vsprintf.c
> +++ b/lib/vsprintf.c
> @@ -1327,7 +1327,9 @@ char *human_readable(char *buf, char *end, const void *addr,
>  			to = i;
>  	}
>  
> -	if (value)
> +	if (spec.precision >= 0 && spec.precision <= 3 && value)
> +		index = (fls64(value) - 1) / 10;
> +	else if (value)
>  		index = __ffs64(value) / 10;
>  	else
>  		index = 0;
> @@ -1336,6 +1338,22 @@ char *human_readable(char *buf, char *end, const void *addr,
>  	/* Print numeric part */
>  	buf = number(buf, end, value >> (index * 10), default_dec_spec);
>  
> +	/* Print precision part if asked */
> +	if (spec.precision > 0 && spec.precision <= 3 && index) {
> +		unsigned int remainder;
> +
> +		remainder = (value >> (index - 1) * 10) % 1024;
> +		for (i = 0; i < spec.precision; i++)
> +			remainder *= 10;
> +		remainder >>= 10;
> +
> +		/* Period... */
> +		buf = put_one_char(buf, end, '.');
> +
> +		/* ...and remainder part */
> +		buf = number(buf, end, remainder, spec);
> +	}
> +
>  	/* Space between numeric part and units */
>  	buf = put_one_char(buf, end, ' ');