[081/118] include/linux/units.h: add helpers for kelvin to/from Celsius conversion

Commit Message

Andrew Morton Jan. 31, 2020, 6:15 a.m. UTC

From: Akinobu Mita <[e-mail]>
Subject: include/linux/units.h: add helpers for kelvin to/from Celsius conversion

Patch series "add header file for kelvin to/from Celsius conversion
helpers", v4.

There are several helper macros to convert kelvin to/from Celsius in
<linux/thermal.h> for thermal drivers.  These are useful for any other
drivers or subsystems, but it's odd to include <linux/thermal.h> just for
the helpers.

This adds a new <linux/units.h> that provides the equivalent inline
functions for any drivers or subsystems, and switches all the users of
conversion helpers in <linux/thermal.h> to use <linux/units.h> helpers.


This patch (of 12):

There are several helper macros to convert kelvin to/from Celsius in
<linux/thermal.h> for thermal drivers.  These are useful for any other
drivers or subsystems, but it's odd to include <linux/thermal.h> just for
the helpers.

This adds a new <linux/units.h> that provides the equivalent inline
functions for any drivers or subsystems.  It is intended to replace the
helpers in <linux/thermal.h>.

Link: http://lkml.kernel.org/r/[e-mail]
Signed-off-by: Akinobu Mita <[e-mail]>
Reviewed-by: Andy Shevchenko <[e-mail]>
Cc: Sujith Thomas <[e-mail]>
Cc: Darren Hart <[e-mail]>
Cc: Zhang Rui <[e-mail]>
Cc: Daniel Lezcano <[e-mail]>
Cc: Amit Kucheria <[e-mail]>
Cc: Jean Delvare <[e-mail]>
Cc: Guenter Roeck <[e-mail]>
Cc: Keith Busch <[e-mail]>
Cc: Jens Axboe <[e-mail]>
Cc: Christoph Hellwig <[e-mail]>
Cc: Sagi Grimberg <[e-mail]>
Cc: Kalle Valo <[e-mail]>
Cc: Stanislaw Gruszka <[e-mail]>
Cc: Johannes Berg <[e-mail]>
Cc: Emmanuel Grumbach <[e-mail]>
Cc: Luca Coelho <[e-mail]>
Cc: Jonathan Cameron <[e-mail]>
Cc: Hartmut Knaack <[e-mail]>
Cc: Lars-Peter Clausen <[e-mail]>
Cc: Peter Meerwald-Stadler <[e-mail]>
Cc: Andy Shevchenko <[e-mail]>
Cc: Jonathan Cameron <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
---

 include/linux/units.h |   84 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 84 insertions(+)

Patch

--- /dev/null
+++ a/include/linux/units.h
@@ -0,0 +1,84 @@ 
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _LINUX_UNITS_H
+#define _LINUX_UNITS_H
+
+#include <linux/kernel.h>
+
+#define ABSOLUTE_ZERO_MILLICELSIUS -273150
+
+static inline long milli_kelvin_to_millicelsius(long t)
+{
+	return t + ABSOLUTE_ZERO_MILLICELSIUS;
+}
+
+static inline long millicelsius_to_milli_kelvin(long t)
+{
+	return t - ABSOLUTE_ZERO_MILLICELSIUS;
+}
+
+#define MILLIDEGREE_PER_DEGREE 1000
+#define MILLIDEGREE_PER_DECIDEGREE 100
+
+static inline long kelvin_to_millicelsius(long t)
+{
+	return milli_kelvin_to_millicelsius(t * MILLIDEGREE_PER_DEGREE);
+}
+
+static inline long millicelsius_to_kelvin(long t)
+{
+	t = millicelsius_to_milli_kelvin(t);
+
+	return DIV_ROUND_CLOSEST(t, MILLIDEGREE_PER_DEGREE);
+}
+
+static inline long deci_kelvin_to_celsius(long t)
+{
+	t = milli_kelvin_to_millicelsius(t * MILLIDEGREE_PER_DECIDEGREE);
+
+	return DIV_ROUND_CLOSEST(t, MILLIDEGREE_PER_DEGREE);
+}
+
+static inline long celsius_to_deci_kelvin(long t)
+{
+	t = millicelsius_to_milli_kelvin(t * MILLIDEGREE_PER_DEGREE);
+
+	return DIV_ROUND_CLOSEST(t, MILLIDEGREE_PER_DECIDEGREE);
+}
+
+/**
+ * deci_kelvin_to_millicelsius_with_offset - convert Kelvin to Celsius
+ * @t: temperature value in decidegrees Kelvin
+ * @offset: difference between Kelvin and Celsius in millidegrees
+ *
+ * Return: temperature value in millidegrees Celsius
+ */
+static inline long deci_kelvin_to_millicelsius_with_offset(long t, long offset)
+{
+	return t * MILLIDEGREE_PER_DECIDEGREE - offset;
+}
+
+static inline long deci_kelvin_to_millicelsius(long t)
+{
+	return milli_kelvin_to_millicelsius(t * MILLIDEGREE_PER_DECIDEGREE);
+}
+
+static inline long millicelsius_to_deci_kelvin(long t)
+{
+	t = millicelsius_to_milli_kelvin(t);
+
+	return DIV_ROUND_CLOSEST(t, MILLIDEGREE_PER_DECIDEGREE);
+}
+
+static inline long kelvin_to_celsius(long t)
+{
+	return t + DIV_ROUND_CLOSEST(ABSOLUTE_ZERO_MILLICELSIUS,
+				     MILLIDEGREE_PER_DEGREE);
+}
+
+static inline long celsius_to_kelvin(long t)
+{
+	return t - DIV_ROUND_CLOSEST(ABSOLUTE_ZERO_MILLICELSIUS,
+				     MILLIDEGREE_PER_DEGREE);
+}
+
+#endif /* _LINUX_UNITS_H */