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

[Andy Shevchenko]

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

Signed-off-by: Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>
---
 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, ' ');
 
-- 
2.6.4