power_supply: Add min/max alert properties for CAPACITY, TEMP, TEMP_AMBIENT

Minimum and maximum alerts on power supply properties will help or allow
the user space to "proactively" create policies like connect/disconnect
charger or stop/start the user apps based on capacity or temperature
parameters.

These parameters can be used to avoid unnecessary polling from user space
and even from kernel space if the underlying HW can support INT triggers
(ex: max17042/47).

This patch adds the following power supply alert type properties:

 CAPACITY_ALERT_MIN
 CAPACITY_ALERT_MAX
 TEMP_ALERT_MIN
 TEMP_ALERT_MAX
 TEMP_AMBIENT_ALERT_MIN
 TEMP_AMBIENT_ALERT_MAX

Signed-off-by: Ramakrishna Pallala <ramakrishna.pallala@intel.com>
Signed-off-by: Anton Vorontsov <anton.vorontsov@linaro.org>

Documentation/power/power_supply_class.txt

@@ -119,11 +119,17 @@ CONSTANT_CHARGE_VOLTAGE - constant charge voltage programmed by charger.
 ENERGY_FULL, ENERGY_EMPTY - same as above but for energy.
 
 CAPACITY - capacity in percents.
+CAPACITY_ALERT_MIN - minimum capacity alert value in percents.
+CAPACITY_ALERT_MAX - maximum capacity alert value in percents.
 CAPACITY_LEVEL - capacity level. This corresponds to
 POWER_SUPPLY_CAPACITY_LEVEL_*.
 
 TEMP - temperature of the power supply.
+TEMP_ALERT_MIN - minimum battery temperature alert value in milli centigrade.
+TEMP_ALERT_MAX - maximum battery temperature alert value in milli centigrade.
 TEMP_AMBIENT - ambient temperature.
+TEMP_AMBIENT_ALERT_MIN - minimum ambient temperature alert value in milli centigrade.
+TEMP_AMBIENT_ALERT_MAX - maximum ambient temperature alert value in milli centigrade.
 
 TIME_TO_EMPTY - seconds left for battery to be considered empty (i.e.
 while battery powers a load)

drivers/power/power_supply_sysfs.c

@@ -168,9 +168,15 @@ static struct device_attribute power_supply_attrs[] = {
 	POWER_SUPPLY_ATTR(energy_now),
 	POWER_SUPPLY_ATTR(energy_avg),
 	POWER_SUPPLY_ATTR(capacity),
+	POWER_SUPPLY_ATTR(capacity_alert_min),
+	POWER_SUPPLY_ATTR(capacity_alert_max),
 	POWER_SUPPLY_ATTR(capacity_level),
 	POWER_SUPPLY_ATTR(temp),
+	POWER_SUPPLY_ATTR(temp_alert_min),
+	POWER_SUPPLY_ATTR(temp_alert_max),
 	POWER_SUPPLY_ATTR(temp_ambient),
+	POWER_SUPPLY_ATTR(temp_ambient_alert_min),
+	POWER_SUPPLY_ATTR(temp_ambient_alert_max),
 	POWER_SUPPLY_ATTR(time_to_empty_now),
 	POWER_SUPPLY_ATTR(time_to_empty_avg),
 	POWER_SUPPLY_ATTR(time_to_full_now),

include/linux/power_supply.h

@@ -118,9 +118,15 @@ enum power_supply_property {
 	POWER_SUPPLY_PROP_ENERGY_NOW,
 	POWER_SUPPLY_PROP_ENERGY_AVG,
 	POWER_SUPPLY_PROP_CAPACITY, /* in percents! */
+	POWER_SUPPLY_PROP_CAPACITY_ALERT_MIN, /* in percents! */
+	POWER_SUPPLY_PROP_CAPACITY_ALERT_MAX, /* in percents! */
 	POWER_SUPPLY_PROP_CAPACITY_LEVEL,
 	POWER_SUPPLY_PROP_TEMP,
+	POWER_SUPPLY_PROP_TEMP_ALERT_MIN,
+	POWER_SUPPLY_PROP_TEMP_ALERT_MAX,
 	POWER_SUPPLY_PROP_TEMP_AMBIENT,
+	POWER_SUPPLY_PROP_TEMP_AMBIENT_ALERT_MIN,
+	POWER_SUPPLY_PROP_TEMP_AMBIENT_ALERT_MAX,
 	POWER_SUPPLY_PROP_TIME_TO_EMPTY_NOW,
 	POWER_SUPPLY_PROP_TIME_TO_EMPTY_AVG,
 	POWER_SUPPLY_PROP_TIME_TO_FULL_NOW,