The user thresholds mechanism is a way to have the userspace to tell
the thermal framework to send a notification when a temperature limit
is crossed. There is no id, no hysteresis, just the temperature and
the direction of the limit crossing. That means we can be notified
when a threshold is crossed the way up only, or the way down only or
both ways. That allows to create hysteresis values if it is needed.
A threshold can be added, deleted or flushed. The latter means all
thresholds belonging to a thermal zone will be deleted.
When a threshold is added:
- if the same threshold (temperature and direction) exists, an error
is returned
- if a threshold is specified with the same temperature but a
different direction, the specified direction is added
- if there is no threshold with the same temperature then it is
created
When a threshold is deleted:
- if the same threshold (temperature and direction) exists, it is
deleted
- if a threshold is specified with the same temperature but a
different direction, the specified direction is removed
- if there is no threshold with the same temperature, then an error
is returned
When the threshold are flushed:
- All thresholds related to a thermal zone are deleted
When a threshold is crossed:
- the userspace does not need to know which threshold(s) have been
crossed, it will be notified with the current temperature and the
previous temperature
- if multiple thresholds have been crossed between two updates only
one notification will be send to the userspace, it is pointless to
send a notification per thresholds crossed as the userspace can
handle that easily when it has the temperature delta information
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Link: https://patch.msgid.link/20240923100005.2532430-2-daniel.lezcano@linaro.org
[ rjw: Subject edit, use BIT(0) and BIT(1) in symbol definitions ]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
445936f9e2