units: Add SI metric prefix definitions

Sometimes it's useful to have well-defined SI metric prefix to be used
to self-describe the formulas or equations.

List most popular ones in the units.h.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Wolfram Sang <wsa@kernel.org>

diff --git a/include/linux/units.h b/include/linux/units.h
index dcc30a53fa939eeee7dea4a4408e9be09854f5bc..4a25e0cc8fb333d19529c55dc99d6523a4ad380e 100644 (file)
--- a/include/linux/units.h
+++ b/include/linux/units.h
@@ -4,6 +4,22 @@
 
 #include <linux/math.h>
 
+/* Metric prefixes in accordance with Système international (d'unités) */
+#define PETA   1000000000000000ULL
+#define TERA   1000000000000ULL
+#define GIGA   1000000000UL
+#define MEGA   1000000UL
+#define KILO   1000UL
+#define HECTO  100UL
+#define DECA   10UL
+#define DECI   10UL
+#define CENTI  100UL
+#define MILLI  1000UL
+#define MICRO  1000000UL
+#define NANO   1000000000UL
+#define PICO   1000000000000ULL
+#define FEMTO  1000000000000000ULL
+
 #define MILLIWATT_PER_WATT     1000L
 #define MICROWATT_PER_MILLIWATT        1000L
 #define MICROWATT_PER_WATT     1000000L