hwmon: Support set_trips() of thermal device ops

Support set_trips() callback of thermal device ops. This allows HWMON
device to operatively notify thermal core about temperature changes, which
is very handy to have in a case where HWMON sensor is used by CPU thermal
zone that performs passive cooling and emergency shutdown on overheat.
Thermal core will be able to react faster to temperature changes.

The set_trips() callback is entirely optional. If HWMON sensor doesn't
support setting thermal trips, then the callback is a NO-OP. The dummy
callback has no effect on the thermal core. The temperature trips are
either complement the temperature polling mechanism of thermal core or
replace the polling if sensor can set the trips and polling is disabled
by a particular device in a device-tree.
Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
Link: https://lore.kernel.org/r/20210623042231.16008-3-digetx@gmail.comSigned-off-by: Guenter Roeck <linux@roeck-us.net>

drivers/hwmon/hwmon.c

@@ -153,8 +153,44 @@ static int hwmon_thermal_get_temp(void *data, int *temp)
 	return 0;
 }
 
+static int hwmon_thermal_set_trips(void *data, int low, int high)
+{
+	struct hwmon_thermal_data *tdata = data;
+	struct hwmon_device *hwdev = to_hwmon_device(tdata->dev);
+	const struct hwmon_chip_info *chip = hwdev->chip;
+	const struct hwmon_channel_info **info = chip->info;
+	unsigned int i;
+	int err;
+
+	if (!chip->ops->write)
+		return 0;
+
+	for (i = 0; info[i] && info[i]->type != hwmon_temp; i++)
+		continue;
+
+	if (!info[i])
+		return 0;
+
+	if (info[i]->config[tdata->index] & HWMON_T_MIN) {
+		err = chip->ops->write(tdata->dev, hwmon_temp,
+				       hwmon_temp_min, tdata->index, low);
+		if (err && err != -EOPNOTSUPP)
+			return err;
+	}
+
+	if (info[i]->config[tdata->index] & HWMON_T_MAX) {
+		err = chip->ops->write(tdata->dev, hwmon_temp,
+				       hwmon_temp_max, tdata->index, high);
+		if (err && err != -EOPNOTSUPP)
+			return err;
+	}
+
+	return 0;
+}
+
 static const struct thermal_zone_of_device_ops hwmon_thermal_ops = {
 	.get_temp = hwmon_thermal_get_temp,
+	.set_trips = hwmon_thermal_set_trips,
 };
 
 static void hwmon_thermal_remove_sensor(void *data)