thermal: core: genetlink support for events/cmd/sampling

Initially the thermal framework had a very simple notification
mechanism to send generic netlink messages to the userspace.

The notification function was never called from anywhere and the
corresponding dead code was removed. It was probably a first attempt
to introduce the netlink notification.

At LPC2018, the presentation "Linux thermal: User kernel interface",
proposed to create the notifications to the userspace via a kfifo.

The advantage of the kfifo is the performance. It is usually used from
a 1:1 communication channel where a driver captures data and sends it
as fast as possible to a userspace process.

The drawback is that only one process uses the notification channel
exclusively, thus no other process is allowed to use the channel to
get temperature or notifications.

This patch defines a generic netlink API to discover the current
thermal setup and adds event notifications as well as temperature
sampling. As any genetlink protocol, it can evolve and the versioning
allows to keep the backward compatibility.

In order to prevent the user from getting flooded with data on a
single channel, there are two multicast channels, one for the
temperature sampling when the thermal zone is updated and another one
for the events, so the user can get the events only without the
thermal zone temperature sampling.

Also, a list of commands to discover the thermal setup is added and
can be extended when needed.

Reviewed-by: Amit Kucheria <amit.kucheria@linaro.org>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Acked-by: Zhang Rui <rui.zhang@intel.com>
Link: https://lore.kernel.org/r/20200706105538.2159-3-daniel.lezcano@linaro.org

1 files changed, 0 insertions, 17 deletions

diff --git a/include/linux/thermal.h b/include/linux/thermal.h
index 108251f23e5c..42ef807e5d84 100644
--- a/include/linux/thermal.h
+++ b/include/linux/thermal.h
@@ -37,18 +37,6 @@ struct thermal_cooling_device;
 struct thermal_instance;
 struct thermal_attr;
 
-enum thermal_device_mode {
-	THERMAL_DEVICE_DISABLED = 0,
-	THERMAL_DEVICE_ENABLED,
-};
-
-enum thermal_trip_type {
-	THERMAL_TRIP_ACTIVE = 0,
-	THERMAL_TRIP_PASSIVE,
-	THERMAL_TRIP_HOT,
-	THERMAL_TRIP_CRITICAL,
-};
-
 enum thermal_trend {
 	THERMAL_TREND_STABLE, /* temperature is stable */
 	THERMAL_TREND_RAISING, /* temperature is raising */
@@ -303,11 +291,6 @@ struct thermal_zone_params {
 	int offset;
 };
 
-struct thermal_genl_event {
-	u32 orig;
-	enum events event;
-};
-
 /**
  * struct thermal_zone_of_device_ops - scallbacks for handling DT based zones
  *