On Sun, 2009-03-01 at 21:03 +0800, Jean Delvare wrote:
> The exact offset between Kelvin and degree Celsius is 273.15. However
> ACPI handles temperature values with a single decimal place. As a
> consequence, some implementations use an offset of 273.1 and others
> use an offset of 273.2. Try to find out which one is being used, to
> present the most accurate and visually appealing number.
>
> Tested on a Sony Vaio PGC-GR214EP (which uses 273.1) and a Lenovo
> Thinkpad T60p (which uses 273.2).
Sounds reasonable.
Acked-by: Zhang Rui <rui.zhang@xxxxxxxxx>
>
> Signed-off-by: Jean Delvare <khali@xxxxxxxxxxxx>
> Cc: Zhang Rui<rui.zhang@xxxxxxxxx>
> Cc: Len Brown <len.brown@xxxxxxxxx>
> ---
> Blame the mess on whoever decided that ACPI temperature would be
> expressed in the least adapted unit in the world :(
>
> Without this patch, I have the following sensors output:
>
> acpitz-virtual-0
> Adapter: Virtual device
> temp1: +44.9 C (crit = +89.9 C)
>
> With the patch I instead have:
>
> acpitz-virtual-0
> Adapter: Virtual device
> temp1: +45.0 C (crit = +90.0 C)
>
> Which I think is much easier to read.
>
> drivers/acpi/thermal.c | 42 +++++++++++++++++++++++++++++++++++-------
> 1 file changed, 35 insertions(+), 7 deletions(-)
>
> --- linux-2.6.29-rc6.orig/drivers/acpi/thermal.c 2009-01-17 09:06:19.000000000 +0100
> +++ linux-2.6.29-rc6/drivers/acpi/thermal.c 2009-03-01 13:51:45.000000000 +0100
> @@ -193,6 +193,7 @@ struct acpi_thermal {
> struct timer_list timer;
> struct thermal_zone_device *thermal_zone;
> int tz_enabled;
> + int kelvin_offset;
> struct mutex lock;
> };
>
> @@ -952,7 +953,7 @@ static void acpi_thermal_check(void *dat
> }
>
> /* sys I/F for generic thermal sysfs support */
> -#define KELVIN_TO_MILLICELSIUS(t) (t * 100 - 273200)
> +#define KELVIN_TO_MILLICELSIUS(t, off) (((t) - (off)) * 100)
>
> static int thermal_get_temp(struct thermal_zone_device *thermal, char *buf)
> {
> @@ -966,7 +967,8 @@ static int thermal_get_temp(struct therm
> if (result)
> return result;
>
> - return sprintf(buf, "%ld\n", KELVIN_TO_MILLICELSIUS(tz->temperature));
> + return sprintf(buf, "%ld\n", KELVIN_TO_MILLICELSIUS(tz->temperature,
> + tz->kelvin_offset));
> }
>
> static const char enabled[] = "kernel";
> @@ -1061,21 +1063,24 @@ static int thermal_get_trip_temp(struct
> if (tz->trips.critical.flags.valid) {
> if (!trip)
> return sprintf(buf, "%ld\n", KELVIN_TO_MILLICELSIUS(
> - tz->trips.critical.temperature));
> + tz->trips.critical.temperature,
> + tz->kelvin_offset));
> trip--;
> }
>
> if (tz->trips.hot.flags.valid) {
> if (!trip)
> return sprintf(buf, "%ld\n", KELVIN_TO_MILLICELSIUS(
> - tz->trips.hot.temperature));
> + tz->trips.hot.temperature,
> + tz->kelvin_offset));
> trip--;
> }
>
> if (tz->trips.passive.flags.valid) {
> if (!trip)
> return sprintf(buf, "%ld\n", KELVIN_TO_MILLICELSIUS(
> - tz->trips.passive.temperature));
> + tz->trips.passive.temperature,
> + tz->kelvin_offset));
> trip--;
> }
>
> @@ -1083,7 +1088,8 @@ static int thermal_get_trip_temp(struct
> tz->trips.active[i].flags.valid; i++) {
> if (!trip)
> return sprintf(buf, "%ld\n", KELVIN_TO_MILLICELSIUS(
> - tz->trips.active[i].temperature));
> + tz->trips.active[i].temperature,
> + tz->kelvin_offset));
> trip--;
> }
>
> @@ -1096,7 +1102,8 @@ static int thermal_get_crit_temp(struct
>
> if (tz->trips.critical.flags.valid) {
> *temperature = KELVIN_TO_MILLICELSIUS(
> - tz->trips.critical.temperature);
> + tz->trips.critical.temperature,
> + tz->kelvin_offset);
> return 0;
> } else
> return -EINVAL;
> @@ -1649,6 +1656,25 @@ static int acpi_thermal_get_info(struct
> return 0;
> }
>
> +/*
> + * The exact offset between Kelvin and degree Celsius is 273.15. However ACPI
> + * handles temperature values with a single decimal place. As a consequence,
> + * some implementations use an offset of 273.1 and others use an offset of
> + * 273.2. Try to find out which one is being used, to present the most
> + * accurate and visually appealing number.
> + *
> + * The heuristic below should work for all ACPI thermal zones which have a
> + * critical trip point with a value being a multiple of 0.5 degree Celsius.
> + */
> +static void acpi_thermal_guess_offset(struct acpi_thermal *tz)
> +{
> + if (tz->trips.critical.flags.valid &&
> + (tz->trips.critical.temperature % 5) == 1)
> + tz->kelvin_offset = 2731;
> + else
> + tz->kelvin_offset = 2732;
> +}
> +
> static int acpi_thermal_add(struct acpi_device *device)
> {
> int result = 0;
> @@ -1675,6 +1701,8 @@ static int acpi_thermal_add(struct acpi_
> if (result)
> goto free_memory;
>
> + acpi_thermal_guess_offset(tz);
> +
> result = acpi_thermal_register_thermal_zone(tz);
> if (result)
> goto free_memory;
>
>
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