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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: Jean Delvare <khali@linux-fr.org>
This commit is contained in:
Jean Delvare 2010-03-05 22:17:21 +01:00
parent 4f3f51bc21
commit cccfc9c4bb
2 changed files with 36 additions and 0 deletions
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4
Documentation/hwmon/it87
View File

@ -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.

32
drivers/hwmon/it87.c
View File

@ -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) {