Commit cccfc9c4 authored by Jean Delvare's avatar Jean Delvare
Browse files

hwmon: (it87) Validate auto pwm settings 



Before switching to automatic fan control mode, make sure that all the
trip points make sense. Otherwise, the control loop could lead to
weird fan behavior.

Signed-off-by: default avatarJean Delvare <khali@linux-fr.org>
parent 4f3f51bc

Documentation/hwmon/it87

+4 −0
Original line number Diff line number Diff line
@@ -177,3 +177,7 @@ between trip point N and trip point N+1 then the PWM output value is 
the one of trip point N. The automatic control mode is less flexible

than the manual control mode, but it reacts faster, is more robust and

doesn't use CPU cycles.



Trip points must be set properly before switching to automatic fan speed

control mode. The driver will perform basic integrity checks before

actually switching to automatic control mode.

drivers/hwmon/it87.c

+32 −0
Original line number Diff line number Diff line
@@ -719,6 +719,32 @@ static ssize_t set_fan_div(struct device *dev, struct device_attribute *attr, 
	mutex_unlock(&data->update_lock);

	return count;

}



/* Returns 0 if OK, -EINVAL otherwise */

static int check_trip_points(struct device *dev, int nr)

{

	const struct it87_data *data = dev_get_drvdata(dev);

	int i, err = 0;



	if (has_old_autopwm(data)) {

		for (i = 0; i < 3; i++) {

			if (data->auto_temp[nr][i] > data->auto_temp[nr][i + 1])

				err = -EINVAL;

		}

		for (i = 0; i < 2; i++) {

			if (data->auto_pwm[nr][i] > data->auto_pwm[nr][i + 1])

				err = -EINVAL;

		}

	}



	if (err) {

		dev_err(dev, "Inconsistent trip points, not switching to "

			"automatic mode\n");

		dev_err(dev, "Adjust the trip points and try again\n");

	}

	return err;

}



static ssize_t set_pwm_enable(struct device *dev,

		struct device_attribute *attr, const char *buf, size_t count)

{
@@ -731,6 +757,12 @@ static ssize_t set_pwm_enable(struct device *dev, 
	if (strict_strtol(buf, 10, &val) < 0 || val < 0 || val > 2)

		return -EINVAL;



	/* Check trip points before switching to automatic mode */

	if (val == 2) {

		if (check_trip_points(dev, nr) < 0)

			return -EINVAL;

	}



	mutex_lock(&data->update_lock);



	if (val == 0) {