[PATCH 3/3] thermal: Add sysfs binding for cooling device and thermal zone

[lukasz.luba@arm.com]

From: Lukasz Luba <lukasz.luba@arm.com>

Make it possible to bind from userspace a cooling device to an existing
thermal zone. It adds more flexibility in addition to static device tree
definitions. There is also a code for changing trip point connected to
cooling device instance in the thermal zone.

In order to bind a device to a zone, first the proper thermal zone name
must be checked from file:
cat /sys/class/thermal/thermal_zoneX/type
Then that name must be set into cooling device 'bind_tz' file:
echo 'gpu-thermal' > /sys/class/thermal/cooling_deviceY/bind_tz
Next a proper trip point must be chosen for this cooling device:
echo 2 > /sys/class/thermal/thermal_zoneX/cdev_Z_trip_point

To unbind, first set -1 to connected trip point:
echo -1 > /sys/class/thermal/thermal_zoneX/cdev_Z_trip_point
Then unbind the thermal zone from the cooling device:
echo 'gpu-thermal' > /sys/class/thermal/cooling_deviceY/unbind_tz

Signed-off-by: Lukasz Luba <lukasz.luba@arm.com>
---
 drivers/thermal/thermal_sysfs.c | 57 +++++++++++++++++++++++++++++++++
 1 file changed, 57 insertions(+)

diff --git a/drivers/thermal/thermal_sysfs.c b/drivers/thermal/thermal_sysfs.c
index 80c8bae6dd1c..473449b41d55 100644
--- a/drivers/thermal/thermal_sysfs.c
+++ b/drivers/thermal/thermal_sysfs.c
@@ -722,15 +722,72 @@ cur_state_store(struct device *dev, struct device_attribute *attr,
 	return result ? result : count;
 }
 
+static ssize_t
+bind_tz_store(struct device *dev, struct device_attribute *attr,
+		const char *buf, size_t count)
+{
+	struct thermal_cooling_device *cdev = to_cooling_device(dev);
+	struct thermal_zone_device *tz;
+	char *orig, *name;
+	int res = 0;
+
+	orig = kstrndup(buf, count, GFP_KERNEL);
+	if (!orig)
+		return -ENOMEM;
+
+	name = strstrip(orig);
+
+	tz = thermal_zone_get_zone_by_name(name);
+	if (IS_ERR_OR_NULL(tz))
+		return -EINVAL;
+
+	res = thermal_zone_bind_cooling_device(tz, THERMAL_TRIPS_NONE, cdev,
+					       THERMAL_NO_LIMIT,
+					       THERMAL_NO_LIMIT,
+					       THERMAL_WEIGHT_DEFAULT);
+
+	kfree(orig);
+	return res ? res : count;
+}
+
+static ssize_t
+unbind_tz_store(struct device *dev, struct device_attribute *attr,
+		const char *buf, size_t count)
+{
+	struct thermal_cooling_device *cdev = to_cooling_device(dev);
+	struct thermal_zone_device *tz;
+	char *name, *orig;
+	int res = 0;
+
+	orig = kstrndup(buf, count, GFP_KERNEL);
+	if (!orig)
+		return -ENOMEM;
+
+	name = strstrip(orig);
+
+	tz = thermal_zone_get_zone_by_name(name);
+	if (IS_ERR_OR_NULL(tz))
+		return -EINVAL;
+
+	res = thermal_zone_unbind_cooling_device(tz, THERMAL_TRIPS_NONE, cdev);
+
+	kfree(orig);
+	return res ? res : count;
+}
+
 static struct device_attribute
 dev_attr_cdev_type = __ATTR(type, 0444, cdev_type_show, NULL);
 static DEVICE_ATTR_RO(max_state);
 static DEVICE_ATTR_RW(cur_state);
+static DEVICE_ATTR_WO(bind_tz);
+static DEVICE_ATTR_WO(unbind_tz);
 
 static struct attribute *cooling_device_attrs[] = {
 	&dev_attr_cdev_type.attr,
 	&dev_attr_max_state.attr,
 	&dev_attr_cur_state.attr,
+	&dev_attr_bind_tz.attr,
+	&dev_attr_unbind_tz.attr,
 	NULL,
 };
 
-- 
2.17.1