Userspace thermal alert
=======================

Provides the facility for user space to know whether a thermal alert
occurred or not for temperature trip value. This is Supported by adding
a software thermal cooling device.

Features
--------

- Sends an "uevent" notification to user space on tripping the associated
thermal trip point.
"uevent" comes under /sys/class/thermal/cooling_device[0-*].

- sysfs API:
sysfs attributes are represented under
/sys/bus/platform/devices/userspace-alert.

Also a symlink to this is provide with
/sys/class/thermal/cooling_device[0-*]/userspace_alert.

/sys/bus/platform/devices/userspace-alert:
/sys/class/thermal/cooling_device[0-*]/userspace_alert:
    |---thermal_alert_block
    |---thermal_alert

thermal_alert_block
			Read/Write value

			Read: Blocks the read call until an alert occurs or the
			specified duration times out. When alert occurs or if
			alert is already present then read returns immediately
			with value "1". If alert is not there and time out
			happens then read returns with value "0".

			Write: Set the time out duration(in milli seconds) to
			wait when alert is not present. By default this value is
			"0" if not set. Value of "0" wall wait for infinite
			time. When alert occurs or if alert is already present,
			then write value has no significance.

thermal_alert
			 Read only value
			 Read: If alert is present returns "1", otherwise
			 returns "0".


- The trip temperature can be modified at runtime if writable permission is
set in device tree properties of trip temperature.
If alert occurs then by increasing the trip temperature to value greater than
current temperature will make the alert to go off  and user space can wait for
alert again with increased temperature trip.
For trip temperature sysfs, refer Documentation/thermal/sysfs-api.txt.



Note:
-----
This cooling device is intended with single trip temperature. When associated
with multiple trip points, alert will come for every trip temperature except
for the case when temperature goes to lower than the lowest trip temperature.