thermal/core: Make the userspace governor deprecated

The userspace governor is sending temperature when polling is active
and trip point crossed events. Nothing else.

AFAICT, this governor is used with custom kernels making the userspace
governor co-existing with another governor on the same thermal zone
because there was no notification mechanism, implying a hack in the
framework to support this configuration.

The new netlink thermal notification is able to provide more
information than the userspace governor and give the opportunity to
the users of this governor to replace it by a dedicated notification
framework.

The userspace governor will be removed as its usage is no longer
needed.

Add a warning message to tell the userspace governor is deprecated.

Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Reviewed-by: Lukasz Luba <lukasz.luba@arm.com>
Link: https://lore.kernel.org/r/20211019163506.2831454-1-daniel.lezcano@linaro.org

drivers/thermal/gov_user_space.c

@@ -15,6 +15,14 @@
 
 #include "thermal_core.h"
 
+static int user_space_bind(struct thermal_zone_device *tz)
+{
+	pr_warn("Userspace governor deprecated: use thermal netlink "	\
+		"notification instead\n");
+
+	return 0;
+}
+
 /**
  * notify_user_space - Notifies user space about thermal events
  * @tz: thermal_zone_device
@@ -43,5 +51,6 @@ static int notify_user_space(struct thermal_zone_device *tz, int trip)
 static struct thermal_governor thermal_gov_user_space = {
 	.name		= "user_space",
 	.throttle	= notify_user_space,
+	.bind_to_tz	= user_space_bind,
 };
 THERMAL_GOVERNOR_DECLARE(thermal_gov_user_space);