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    SubjectRe: [PATCH v2 1/8] add header file for kelvin to/from Celsius conversion helpers
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    On 28/11/2019 15:54, Akinobu Mita wrote:
    > 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/temperature.h> that provides the equivalent inline
    > functions for any drivers or subsystems. It is intended to replace the
    > helpers in <linux/thermal.h>.
    >
    > Cc: Sujith Thomas <sujith.thomas@intel.com>
    > Cc: Darren Hart <dvhart@infradead.org>
    > Cc: Andy Shevchenko <andy@infradead.org>
    > Cc: Zhang Rui <rui.zhang@intel.com>
    > Cc: Daniel Lezcano <daniel.lezcano@linaro.org>
    > Cc: Amit Kucheria <amit.kucheria@verdurent.com>
    > Cc: Jean Delvare <jdelvare@suse.com>
    > Cc: Guenter Roeck <linux@roeck-us.net>
    > Cc: Keith Busch <kbusch@kernel.org>
    > Cc: Jens Axboe <axboe@fb.com>
    > Cc: Christoph Hellwig <hch@lst.de>
    > Cc: Sagi Grimberg <sagi@grimberg.me>
    > Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
    > ---
    > * v2
    > - add deci_kelvin_to_millicelsius_with_offset() in linux/temperature.h
    > - stop including linux/temperature.h from linux/thermal.h
    >
    > include/linux/temperature.h | 51 +++++++++++++++++++++++++++++++++++++++++++++
    > 1 file changed, 51 insertions(+)
    > create mode 100644 include/linux/temperature.h
    >
    > diff --git a/include/linux/temperature.h b/include/linux/temperature.h
    > new file mode 100644
    > index 0000000..679e70a
    > --- /dev/null
    > +++ b/include/linux/temperature.h
    > @@ -0,0 +1,51 @@
    > +/* SPDX-License-Identifier: GPL-2.0 */
    > +#ifndef _LINUX_TEMPERATURE_H
    > +#define _LINUX_TEMPERATURE_H

    It sounds strange to create a temperature file just for a few conversion
    functions. Why not create an units.h file, so some more conversions
    could be added later (not necessarily related to temperature) ?

    > +#include <linux/kernel.h>
    > +
    > +#define ABSOLUTE_ZERO_MILLICELSIUS -273150
    > +
    > +static inline long kelvin_to_millicelsius(long t)

    Why 'long' ?

    > +{
    > + return t * 1000 + ABSOLUTE_ZERO_MILLICELSIUS;
    > +}
    > +
    > +static inline long millicelsius_to_kelvin(long t)
    > +{
    > + return DIV_ROUND_CLOSEST(t - ABSOLUTE_ZERO_MILLICELSIUS, 1000);

    Please don't duplicate these operations, just do the conversion to the
    right unit and then call a single function.

    Replace the constant by macros like what we find in time64.h.

    eg.
    #define MILLICELSIUS_PER_CELCIUS 1000

    So you can really do the cleanup in all the drivers, like removing:

    drivers/iio/adc/qcom-vadc-common.h:#define KELVINMIL_CELSIUSMIL
    273150
    drivers/iio/pressure/st_pressure_core.c:#define MCELSIUS_PER_CELSIUS
    1000
    drivers/hwmon/xgene-hwmon.c:#define CELSIUS_TO_mCELSIUS(x)
    ((x) * 1000)
    drivers/net/wireless/intel/iwlegacy/common.h:#define
    KELVIN_TO_CELSIUS(x) ((x)-273)
    drivers/net/wireless/intel/iwlegacy/common.h:#define
    CELSIUS_TO_KELVIN(x) ((x)+273)
    drivers/net/wireless/intel/iwlwifi/dvm/dev.h:#define
    KELVIN_TO_CELSIUS(x) ((x)-273)
    drivers/net/wireless/intel/iwlwifi/dvm/dev.h:#define
    CELSIUS_TO_KELVIN(x) ((x)+273)
    drivers/power/supply/sbs-battery.c:#define TEMP_KELVIN_TO_CELSIUS
    2731
    drivers/thermal/armada_thermal.c:#define TO_MCELSIUS(c)
    ((c) * 1000)
    drivers/thermal/rcar_gen3_thermal.c:#define MCELSIUS(temp) ((temp)
    * 1000)
    drivers/thermal/rcar_thermal.c:#define MCELSIUS(temp)
    ((temp) * 1000)
    drivers/thermal/samsung/exynos_tmu.c:#define MCELSIUS 1000
    drivers/thermal/samsung/exynos_tmu.c: temp /= MCELSIUS;
    drivers/thermal/samsung/exynos_tmu.c: hyst /= MCELSIUS;
    drivers/thermal/samsung/exynos_tmu.c: ref = trips[0].temperature /
    MCELSIUS;
    drivers/thermal/samsung/exynos_tmu.c: *temp =
    code_to_temp(data, value) * MCELSIUS;
    drivers/thermal/samsung/exynos_tmu.c: temp /= MCELSIUS;


    > +}
    > +
    > +static inline long deci_kelvin_to_celsius(long t)
    > +{
    > + return DIV_ROUND_CLOSEST(t * 100 + ABSOLUTE_ZERO_MILLICELSIUS, 1000);
    > +}
    > +
    > +static inline long celsius_to_deci_kelvin(long t)
    > +{
    > + return t * 10 - DIV_ROUND_CLOSEST(ABSOLUTE_ZERO_MILLICELSIUS, 100);
    > +}
    > +
    > +/**
    > + * 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 * 100 - offset;
    > +}
    > +
    > +static inline long deci_kelvin_to_millicelsius(long t)
    > +{
    > + return t * 100 + ABSOLUTE_ZERO_MILLICELSIUS;
    > +}
    > +
    > +static inline long millicelsius_to_deci_kelvin(long t)
    > +{
    > + return DIV_ROUND_CLOSEST(t - ABSOLUTE_ZERO_MILLICELSIUS, 100);
    > +}
    > +
    > +#endif /* _LINUX_TEMPERATURE_H */
    >


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