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From: "Rafael J. Wysocki" <rjw@rjwysocki.net>
To: Linux PM <linux-pm@vger.kernel.org>
Cc: LKML <linux-kernel@vger.kernel.org>,
 Daniel Lezcano <daniel.lezcano@linaro.org>,
 Lukasz Luba <lukasz.luba@arm.com>,
 Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
Subject:
 [PATCH v1 14/16] thermal: gov_user_space: Use .trip_crossed() instead of
 .throttle()
Date: Wed, 10 Apr 2024 19:03:10 +0200
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From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

Notifying user space about trip points that have not been crossed is
not particuarly useful, so modity the User Space governor to use the
trip_crossed() callback, which is only invoked for trips that have been
crossed, instead of .throttle() that is invoked for all trips in a
thermal zone every time the zone is updated.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
---

Note: I am not actually sure if there is user space depending on the
current behavior that can be broken by this change.

I can easily imagine trying to implement a complicated governor in user
space that will look at all of the trips in the thermal zone regardless
of whether or not they are crossed, which can be kind of helped by the
current behavior of the user space governor.

However, the total overhead caused by it is considerable and quite
arguably it may not be acceptable at least in some cases.

---
 drivers/thermal/gov_user_space.c |   10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

Index: linux-pm/drivers/thermal/gov_user_space.c
===================================================================
--- linux-pm.orig/drivers/thermal/gov_user_space.c
+++ linux-pm/drivers/thermal/gov_user_space.c
@@ -26,11 +26,13 @@ static int user_space_bind(struct therma
  * notify_user_space - Notifies user space about thermal events
  * @tz: thermal_zone_device
  * @trip: trip point
+ * @crossed_up: whether or not the trip has been crossed on the way up
  *
  * This function notifies the user space through UEvents.
  */
-static int notify_user_space(struct thermal_zone_device *tz,
-			     const struct thermal_trip *trip)
+static void notify_user_space(struct thermal_zone_device *tz,
+			      const struct thermal_trip *trip,
+			      bool crossed_up)
 {
 	char *thermal_prop[5];
 	int i;
@@ -46,13 +48,11 @@ static int notify_user_space(struct ther
 	kobject_uevent_env(&tz->device.kobj, KOBJ_CHANGE, thermal_prop);
 	for (i = 0; i < 4; ++i)
 		kfree(thermal_prop[i]);
-
-	return 0;
 }
 
 static struct thermal_governor thermal_gov_user_space = {
 	.name		= "user_space",
-	.throttle	= notify_user_space,
+	.trip_crossed	= notify_user_space,
 	.bind_to_tz	= user_space_bind,
 };
 THERMAL_GOVERNOR_DECLARE(thermal_gov_user_space);